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[PATCH 00/46] perf tools: Fix and improvements (bpf and overwrite)

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  [PATCH 00/46] perf tools: Fix and improvements (bpf and overwrite) Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:40 +0100
    [PATCH 07/46] perf trace: Print content of bpf-output event Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:40 +0100
      [tip:perf/core] perf trace: Print content of bpf-output event tip-bot for Wang Nan <tipbot@zytor.com> - 2016-02-27 10:50 +0100
    [PATCH 43/46] perf record: Rename variable to make code clear Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:40 +0100
    [PATCH 46/46] perf tools: Don't warn about out of order event if write_backward is used Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 26/46] perf record: Disable buildid cache options by default in switch output mode Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 33/46] perf tools: Operate multiple channels Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 24/46] perf record: Split output into multiple files via '--switch-output' Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 45/46] perf record: Allow generate tracking events at the end of output Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 36/46] perf record: Don't poll on overwrite channel Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 30/46] perf record: Prevent reading invalid data in record__mmap_read Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 31/46] perf tools: Add evlist channel helpers Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 35/46] perf record: Don't read from and poll overwrite channel Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 23/46] perf record: Add '--timestamp-filename' option to append timestamp to output filename Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 25/46] perf record: Force enable --timestamp-filename when --switch-output is provided Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 28/46] perf record: Generate tracking events for process forked by perf Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 21/46] perf record: Turns auxtrace_snapshot_enable into 3 states Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 27/46] perf record: Re-synthesize tracking events after output switching Wang Nan <wangnan0@huawei.com> - 2016-02-26 10:50 +0100
    [PATCH 12/46] perf core: Prepare writing into ring buffer from end Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 19/46] perf record: Extract synthesize code to record__synthesize() Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 11/46] perf core: Set event's default overflow_handler Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 13/46] perf core: Add backward attribute to perf event Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 18/46] perf record: Use WARN_ONCE to replace 'if' condition Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 20/46] perf tools: Add perf_data_file__switch() helper Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 17/46] perf tools: Make ordered_events reusable Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 14/46] perf core: Reduce perf event output overhead by new overflow handler Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 08/46] perf data: Support converting data from bpf_perf_event_output() Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 10/46] perf core: Introduce new ioctl options to pause and resume ring buffer Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
      Re: [PATCH 10/46] perf core: Introduce new ioctl options to pause  and resume ring buffer Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-29 16:40 +0100
        Re: [PATCH 10/46] perf core: Introduce new ioctl options to pause and  resume ring buffer "Wangnan (F)" <wangnan0@huawei.com> - 2016-03-03 03:20 +0100
    [PATCH 09/46] perf data: Explicitly set byte order for integer types Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
    [PATCH 03/46] perf config: Bring perf_default_config to the very beginning at main() Wang Nan <wangnan0@huawei.com> - 2016-02-26 11:00 +0100
      [tip:perf/core] perf config: Bring perf_default_config to the very  beginning at main() tip-bot for Wang Nan <tipbot@zytor.com> - 2016-02-27 10:50 +0100

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#1343984 — [PATCH 11/46] perf core: Set event's default overflow_handler

Set a default event->overflow_handler in perf_event_alloc() so don't
need checking event->overflow_handler in __perf_event_overflow().
Following commits can give a different default overflow_handler.

No extra performance introduced into hot path because in the original
code we still need reading this handler from memory. A conditional branch
is avoided so actually we remove some instructions.

Initial idea comes from Peter at [1].

[1] http://lkml.kernel.org/r/20130708121557.GA17211@twins.programming.kicks-ass.net

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 kernel/events/core.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index a7075ae..ae34061 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6392,10 +6392,7 @@ static int __perf_event_overflow(struct perf_event *event,
 		irq_work_queue(&event->pending);
 	}
 
-	if (event->overflow_handler)
-		event->overflow_handler(event, data, regs);
-	else
-		perf_event_output(event, data, regs);
+	event->overflow_handler(event, data, regs);
 
 	if (*perf_event_fasync(event) && event->pending_kill) {
 		event->pending_wakeup = 1;
@@ -7868,8 +7865,13 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 		context = parent_event->overflow_handler_context;
 	}
 
-	event->overflow_handler	= overflow_handler;
-	event->overflow_handler_context = context;
+	if (overflow_handler) {
+		event->overflow_handler	= overflow_handler;
+		event->overflow_handler_context = context;
+	} else {
+		event->overflow_handler = perf_event_output;
+		event->overflow_handler_context = NULL;
+	}
 
 	perf_event__state_init(event);
 
-- 
1.8.3.4

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#1343985 — [PATCH 13/46] perf core: Add backward attribute to perf event

In perf_event_attr a new bit 'write_backward' is appended to indicate
this event should write ring buffer from its end to beginning.

In perf_output_begin(), prepare ring buffer according this bit.

This patch introduces small overhead into perf_output_begin():
an extra memory read and a conditional branch. Further patch can remove
this overhead by using custom output handler.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 include/linux/perf_event.h      | 5 +++++
 include/uapi/linux/perf_event.h | 3 ++-
 kernel/events/core.c            | 7 +++++++
 kernel/events/ring_buffer.c     | 2 ++
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index b35a61a..0ce1015 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1029,6 +1029,11 @@ static inline bool has_aux(struct perf_event *event)
 	return event->pmu->setup_aux;
 }
 
+static inline bool is_write_backward(struct perf_event *event)
+{
+	return !!event->attr.write_backward;
+}
+
 extern int perf_output_begin(struct perf_output_handle *handle,
 			     struct perf_event *event, unsigned int size);
 extern void perf_output_end(struct perf_output_handle *handle);
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index a3c1903..43fc8d2 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -340,7 +340,8 @@ struct perf_event_attr {
 				comm_exec      :  1, /* flag comm events that are due to an exec */
 				use_clockid    :  1, /* use @clockid for time fields */
 				context_switch :  1, /* context switch data */
-				__reserved_1   : 37;
+				write_backward :  1, /* Write ring buffer from end to beginning */
+				__reserved_1   : 36;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index ae34061..9353154 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8101,6 +8101,13 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
 		goto out;
 
 	/*
+	 * Either writing ring buffer from beginning or from end.
+	 * Mixing is not allowed.
+	 */
+	if (is_write_backward(output_event) != is_write_backward(event))
+		goto out;
+
+	/*
 	 * If both events generate aux data, they must be on the same PMU
 	 */
 	if (has_aux(event) && has_aux(output_event) &&
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 37c11c6..80b1fa7 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -233,6 +233,8 @@ out:
 int perf_output_begin(struct perf_output_handle *handle,
 		      struct perf_event *event, unsigned int size)
 {
+	if (unlikely(is_write_backward(event)))
+		return __perf_output_begin(handle, event, size, true);
 	return __perf_output_begin(handle, event, size, false);
 }
 
-- 
1.8.3.4

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#1343986 — [PATCH 18/46] perf record: Use WARN_ONCE to replace 'if' condition

Following commits will extract kernel and module synthesizing code into
a separated function and call it multiple times. This patch replace
'if (err < 0)' using WARN_ONCE, makes sure the error message show
one time.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/builtin-record.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 7d11162..9dec7e5 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -33,6 +33,7 @@
 #include "util/parse-regs-options.h"
 #include "util/llvm-utils.h"
 #include "util/bpf-loader.h"
+#include "asm/bug.h"
 
 #include <unistd.h>
 #include <sched.h>
@@ -615,17 +616,15 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 
 	err = perf_event__synthesize_kernel_mmap(tool, process_synthesized_event,
 						 machine);
-	if (err < 0)
-		pr_err("Couldn't record kernel reference relocation symbol\n"
-		       "Symbol resolution may be skewed if relocation was used (e.g. kexec).\n"
-		       "Check /proc/kallsyms permission or run as root.\n");
+	WARN_ONCE(err < 0, "Couldn't record kernel reference relocation symbol\n"
+			   "Symbol resolution may be skewed if relocation was used (e.g. kexec).\n"
+			   "Check /proc/kallsyms permission or run as root.\n");
 
 	err = perf_event__synthesize_modules(tool, process_synthesized_event,
 					     machine);
-	if (err < 0)
-		pr_err("Couldn't record kernel module information.\n"
-		       "Symbol resolution may be skewed if relocation was used (e.g. kexec).\n"
-		       "Check /proc/modules permission or run as root.\n");
+	WARN_ONCE(err < 0, "Couldn't record kernel module information.\n"
+			   "Symbol resolution may be skewed if relocation was used (e.g. kexec).\n"
+			   "Check /proc/modules permission or run as root.\n");
 
 	if (perf_guest) {
 		machines__process_guests(&session->machines,
-- 
1.8.3.4

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#1343989 — [PATCH 20/46] perf tools: Add perf_data_file__switch() helper

perf_data_file__switch() closes current output file, renames it, then
open a new one to continue record. It will be used by perf record
to split output into multiple perf.data files.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: He Kuang <hekuang@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/util/data.c | 38 ++++++++++++++++++++++++++++++++++++++
 tools/perf/util/data.h | 11 ++++++++++-
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
index 1921942..6840fc9 100644
--- a/tools/perf/util/data.c
+++ b/tools/perf/util/data.c
@@ -136,3 +136,41 @@ ssize_t perf_data_file__write(struct perf_data_file *file,
 {
 	return writen(file->fd, buf, size);
 }
+
+int perf_data_file__switch(struct perf_data_file *file,
+			   const char *postfix,
+			   size_t pos, bool at_exit)
+{
+	char *new_filepath;
+	int ret;
+
+	if (check_pipe(file))
+		return -EINVAL;
+	if (perf_data_file__is_read(file))
+		return -EINVAL;
+
+	if (asprintf(&new_filepath, "%s.%s", file->path, postfix) < 0)
+		return -ENOMEM;
+
+	/* Only fire a warning, don't return error. */
+	if (rename(file->path, new_filepath))
+		pr_warning("Failed to rename %s to %s\n", file->path, new_filepath);
+
+	if (!at_exit) {
+		close(file->fd);
+		ret = perf_data_file__open(file);
+		if (ret < 0)
+			goto out;
+
+		if (lseek(file->fd, pos, SEEK_SET) == (off_t)-1) {
+			ret = -errno;
+			pr_debug("Failed to lseek to %zu: %s",
+				 pos, strerror(errno));
+			goto out;
+		}
+	}
+	ret = file->fd;
+out:
+	free(new_filepath);
+	return ret;
+}
diff --git a/tools/perf/util/data.h b/tools/perf/util/data.h
index 2b15d0c..ae510ce 100644
--- a/tools/perf/util/data.h
+++ b/tools/perf/util/data.h
@@ -46,5 +46,14 @@ int perf_data_file__open(struct perf_data_file *file);
 void perf_data_file__close(struct perf_data_file *file);
 ssize_t perf_data_file__write(struct perf_data_file *file,
 			      void *buf, size_t size);
-
+/*
+ * If at_exit is set, only rename current perf.data to
+ * perf.data.<postfix>, continue write on original file.
+ * Set at_exit when flushing the last output.
+ *
+ * Return value is fd of new output.
+ */
+int perf_data_file__switch(struct perf_data_file *file,
+			   const char *postfix,
+			   size_t pos, bool at_exit);
 #endif /* __PERF_DATA_H */
-- 
1.8.3.4

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#1343990 — [PATCH 17/46] perf tools: Make ordered_events reusable

ordered_events__free() leaves linked lists and timestamps not cleared,
so unable to be reused after ordered_events__free(). Which is inconvenient
after 'perf record' supports generating multiple perf.data output and
process build-ids for each of them.

Introduce ordered_events__reinit() for this.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: He Kuang <hekuang@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/util/ordered-events.c | 9 +++++++++
 tools/perf/util/ordered-events.h | 1 +
 tools/perf/util/session.c        | 6 +++++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index b1b9e23..fe84df1 100644
--- a/tools/perf/util/ordered-events.c
+++ b/tools/perf/util/ordered-events.c
@@ -308,3 +308,12 @@ void ordered_events__free(struct ordered_events *oe)
 		free(event);
 	}
 }
+
+void ordered_events__reinit(struct ordered_events *oe)
+{
+	ordered_events__deliver_t old_deliver = oe->deliver;
+
+	ordered_events__free(oe);
+	memset(oe, '\0', sizeof(*oe));
+	ordered_events__init(oe, old_deliver);
+}
diff --git a/tools/perf/util/ordered-events.h b/tools/perf/util/ordered-events.h
index f403991..e11468a 100644
--- a/tools/perf/util/ordered-events.h
+++ b/tools/perf/util/ordered-events.h
@@ -49,6 +49,7 @@ void ordered_events__delete(struct ordered_events *oe, struct ordered_event *eve
 int ordered_events__flush(struct ordered_events *oe, enum oe_flush how);
 void ordered_events__init(struct ordered_events *oe, ordered_events__deliver_t deliver);
 void ordered_events__free(struct ordered_events *oe);
+void ordered_events__reinit(struct ordered_events *oe);
 
 static inline
 void ordered_events__set_alloc_size(struct ordered_events *oe, u64 size)
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 40b7a0d..ab3a296 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1857,7 +1857,11 @@ out:
 out_err:
 	ui_progress__finish();
 	perf_session__warn_about_errors(session);
-	ordered_events__free(&session->ordered_events);
+	/*
+	 * We may switching perf.data output, make ordered_events
+	 * reusable.
+	 */
+	ordered_events__reinit(&session->ordered_events);
 	auxtrace__free_events(session);
 	session->one_mmap = false;
 	return err;
-- 
1.8.3.4

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#1343991 — [PATCH 14/46] perf core: Reduce perf event output overhead by new overflow handler

By creating onward and backward specific overflow handlers and setting
them according to event's backward setting, normal sampling events
don't need checking backward setting of an event any more.

This is the last patch of backward writing patchset. After this patch,
there's no extra overhead introduced to the fast path of sampling
output.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 include/linux/perf_event.h  | 17 +++++++++++++++--
 kernel/events/core.c        | 41 ++++++++++++++++++++++++++++++++++++-----
 kernel/events/ring_buffer.c | 12 ++++++++++++
 3 files changed, 63 insertions(+), 7 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 0ce1015..e466cc6 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -827,9 +827,15 @@ extern int perf_event_overflow(struct perf_event *event,
 				 struct perf_sample_data *data,
 				 struct pt_regs *regs);
 
+extern void perf_event_output_onward(struct perf_event *event,
+				     struct perf_sample_data *data,
+				     struct pt_regs *regs);
+extern void perf_event_output_backward(struct perf_event *event,
+				       struct perf_sample_data *data,
+				       struct pt_regs *regs);
 extern void perf_event_output(struct perf_event *event,
-				struct perf_sample_data *data,
-				struct pt_regs *regs);
+			      struct perf_sample_data *data,
+			      struct pt_regs *regs);
 
 extern void
 perf_event_header__init_id(struct perf_event_header *header,
@@ -1036,6 +1042,13 @@ static inline bool is_write_backward(struct perf_event *event)
 
 extern int perf_output_begin(struct perf_output_handle *handle,
 			     struct perf_event *event, unsigned int size);
+extern int perf_output_begin_onward(struct perf_output_handle *handle,
+				    struct perf_event *event,
+				    unsigned int size);
+extern int perf_output_begin_backward(struct perf_output_handle *handle,
+				      struct perf_event *event,
+				      unsigned int size);
+
 extern void perf_output_end(struct perf_output_handle *handle);
 extern unsigned int perf_output_copy(struct perf_output_handle *handle,
 			     const void *buf, unsigned int len);
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 9353154..ce70f54 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5531,9 +5531,13 @@ void perf_prepare_sample(struct perf_event_header *header,
 	}
 }
 
-void perf_event_output(struct perf_event *event,
-			struct perf_sample_data *data,
-			struct pt_regs *regs)
+static void __always_inline
+__perf_event_output(struct perf_event *event,
+		    struct perf_sample_data *data,
+		    struct pt_regs *regs,
+		    int (*output_begin)(struct perf_output_handle *,
+					struct perf_event *,
+					unsigned int))
 {
 	struct perf_output_handle handle;
 	struct perf_event_header header;
@@ -5543,7 +5547,7 @@ void perf_event_output(struct perf_event *event,
 
 	perf_prepare_sample(&header, data, event, regs);
 
-	if (perf_output_begin(&handle, event, header.size))
+	if (output_begin(&handle, event, header.size))
 		goto exit;
 
 	perf_output_sample(&handle, &header, data, event);
@@ -5554,6 +5558,30 @@ exit:
 	rcu_read_unlock();
 }
 
+void
+perf_event_output_onward(struct perf_event *event,
+			 struct perf_sample_data *data,
+			 struct pt_regs *regs)
+{
+	__perf_event_output(event, data, regs, perf_output_begin_onward);
+}
+
+void
+perf_event_output_backward(struct perf_event *event,
+			   struct perf_sample_data *data,
+			   struct pt_regs *regs)
+{
+	__perf_event_output(event, data, regs, perf_output_begin_backward);
+}
+
+void
+perf_event_output(struct perf_event *event,
+		  struct perf_sample_data *data,
+		  struct pt_regs *regs)
+{
+	__perf_event_output(event, data, regs, perf_output_begin);
+}
+
 /*
  * read event_id
  */
@@ -7868,8 +7896,11 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 	if (overflow_handler) {
 		event->overflow_handler	= overflow_handler;
 		event->overflow_handler_context = context;
+	} else if (is_write_backward(event)){
+		event->overflow_handler = perf_event_output_backward;
+		event->overflow_handler_context = NULL;
 	} else {
-		event->overflow_handler = perf_event_output;
+		event->overflow_handler = perf_event_output_onward;
 		event->overflow_handler_context = NULL;
 	}
 
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 80b1fa7..7e30e012 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -230,6 +230,18 @@ out:
 	return -ENOSPC;
 }
 
+int perf_output_begin_onward(struct perf_output_handle *handle,
+			     struct perf_event *event, unsigned int size)
+{
+	return __perf_output_begin(handle, event, size, false);
+}
+
+int perf_output_begin_backward(struct perf_output_handle *handle,
+			       struct perf_event *event, unsigned int size)
+{
+	return __perf_output_begin(handle, event, size, true);
+}
+
 int perf_output_begin(struct perf_output_handle *handle,
 		      struct perf_event *event, unsigned int size)
 {
-- 
1.8.3.4

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#1343992 — [PATCH 08/46] perf data: Support converting data from bpf_perf_event_output()

bpf_perf_event_output() outputs data through sample->raw_data. This
patch adds support to convert those data into CTF. A python script
then can be used to process output data from BPF programs.

Test result:

 # cat ./test_bpf_output_2.c
 /************************ BEGIN **************************/
 #include <uapi/linux/bpf.h>
 struct bpf_map_def {
 	unsigned int type;
 	unsigned int key_size;
 	unsigned int value_size;
 	unsigned int max_entries;
 };
 #define SEC(NAME) __attribute__((section(NAME), used))
 static u64 (*ktime_get_ns)(void) =
 	(void *)BPF_FUNC_ktime_get_ns;
 static int (*trace_printk)(const char *fmt, int fmt_size, ...) =
 	(void *)BPF_FUNC_trace_printk;
 static int (*get_smp_processor_id)(void) =
 	(void *)BPF_FUNC_get_smp_processor_id;
 static int (*perf_event_output)(void *, struct bpf_map_def *, int, void *, unsigned long) =
 	(void *)BPF_FUNC_perf_event_output;

 struct bpf_map_def SEC("maps") channel = {
 	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
 	.key_size = sizeof(int),
 	.value_size = sizeof(u32),
 	.max_entries = __NR_CPUS__,
 };

 static inline int __attribute__((always_inline))
 func(void *ctx, int type)
 {
 	struct {
 		u64 ktime;
 		int type;
 	} __attribute__((packed)) output_data;
 	char error_data[] = "Error: failed to output\n";
 	int err;

 	output_data.type = type;
 	output_data.ktime = ktime_get_ns();
 	err = perf_event_output(ctx, &channel, get_smp_processor_id(),
 				&output_data, sizeof(output_data));
 	if (err)
 		trace_printk(error_data, sizeof(error_data));
 	return 0;
 }
 SEC("func_begin=sys_nanosleep")
 int func_begin(void *ctx) {return func(ctx, 1);}
 SEC("func_end=sys_nanosleep%return")
 int func_end(void *ctx) { return func(ctx, 2);}
 char _license[] SEC("license") = "GPL";
 int _version SEC("version") = LINUX_VERSION_CODE;
 /************************* END ***************************/

 # ./perf record -e bpf-output/no-inherit,name=evt/ \
                 -e ./test_bpf_output_2.c/map:channel.event=evt/ \
                 usleep 100000
 [ perf record: Woken up 1 times to write data ]
 [ perf record: Captured and wrote 0.012 MB perf.data (2 samples) ]

 # ./perf script
          usleep 14942 92503.198504: evt:  ffffffff810e0ba1 sys_nanosleep (/lib/modules/4.3.0....
          usleep 14942 92503.298562: evt:  ffffffff810585e9 kretprobe_trampoline_holder (/lib....

 # ./perf data convert --to-ctf ./out.ctf
 [ perf data convert: Converted 'perf.data' into CTF data './out.ctf' ]
 [ perf data convert: Converted and wrote 0.000 MB (2 samples) ]

 # babeltrace ./out.ctf
 [01:41:43.198504134] (+?.?????????) evt: { cpu_id = 0 }, { perf_ip = 0xFFFFFFFF810E0BA1, perf_tid = 14942, perf_pid = 14942, perf_id = 1044, raw_len = 3, raw_data = [ [0] = 0x32C0C07B, [1] = 0x5421, [2] = 0x1 ] }
 [01:41:43.298562257] (+0.100058123) evt: { cpu_id = 0 }, { perf_ip = 0xFFFFFFFF810585E9, perf_tid = 14942, perf_pid = 14942, perf_id = 1044, raw_len = 3, raw_data = [ [0] = 0x38B77FAA, [1] = 0x5421, [2] = 0x2 ] }

 # cat ./test_bpf_output_2.py
 from babeltrace import TraceCollection
 tc = TraceCollection()
 tc.add_trace('./out.ctf', 'ctf')
 d = {1:[], 2:[]}
 for event in tc.events:
     if not event.name.startswith('evt'):
         continue
     raw_data = event['raw_data']
     (time, type) = ((raw_data[0] + (raw_data[1] << 32)), raw_data[2])
     d[type].append(time)
 print(list(map(lambda i: d[2][i] - d[1][i], range(len(d[1])))));

 # python3 ./test_bpf_output_2.py
 [100056879]

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/util/data-convert-bt.c | 112 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 111 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
index 6729f4d..1f608a6 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/tools/perf/util/data-convert-bt.c
@@ -352,6 +352,84 @@ static int add_tracepoint_values(struct ctf_writer *cw,
 	return ret;
 }
 
+static int
+add_bpf_output_values(struct bt_ctf_event_class *event_class,
+		      struct bt_ctf_event *event,
+		      struct perf_sample *sample)
+{
+	struct bt_ctf_field_type *len_type, *seq_type;
+	struct bt_ctf_field *len_field, *seq_field;
+	unsigned int raw_size = sample->raw_size;
+	unsigned int nr_elements = raw_size / sizeof(u32);
+	unsigned int i;
+	int ret;
+
+	if (nr_elements * sizeof(u32) != raw_size)
+		pr_warning("Incorrect raw_size (%u) in bpf output event, skip %lu bytes\n",
+			   raw_size, nr_elements * sizeof(u32) - raw_size);
+
+	len_type = bt_ctf_event_class_get_field_by_name(event_class, "raw_len");
+	len_field = bt_ctf_field_create(len_type);
+	if (!len_field) {
+		pr_err("failed to create 'raw_len' for bpf output event\n");
+		ret = -1;
+		goto put_len_type;
+	}
+
+	ret = bt_ctf_field_unsigned_integer_set_value(len_field, nr_elements);
+	if (ret) {
+		pr_err("failed to set field value for raw_len\n");
+		goto put_len_field;
+	}
+	ret = bt_ctf_event_set_payload(event, "raw_len", len_field);
+	if (ret) {
+		pr_err("failed to set payload to raw_len\n");
+		goto put_len_field;
+	}
+
+	seq_type = bt_ctf_event_class_get_field_by_name(event_class, "raw_data");
+	seq_field = bt_ctf_field_create(seq_type);
+	if (!seq_field) {
+		pr_err("failed to create 'raw_data' for bpf output event\n");
+		ret = -1;
+		goto put_seq_type;
+	}
+
+	ret = bt_ctf_field_sequence_set_length(seq_field, len_field);
+	if (ret) {
+		pr_err("failed to set length of 'raw_data'\n");
+		goto put_seq_field;
+	}
+
+	for (i = 0; i < nr_elements; i++) {
+		struct bt_ctf_field *elem_field =
+			bt_ctf_field_sequence_get_field(seq_field, i);
+
+		ret = bt_ctf_field_unsigned_integer_set_value(elem_field,
+				((u32 *)(sample->raw_data))[i]);
+
+		bt_ctf_field_put(elem_field);
+		if (ret) {
+			pr_err("failed to set raw_data[%d]\n", i);
+			goto put_seq_field;
+		}
+	}
+
+	ret = bt_ctf_event_set_payload(event, "raw_data", seq_field);
+	if (ret)
+		pr_err("failed to set payload for raw_data\n");
+
+put_seq_field:
+	bt_ctf_field_put(seq_field);
+put_seq_type:
+	bt_ctf_field_type_put(seq_type);
+put_len_field:
+	bt_ctf_field_put(len_field);
+put_len_type:
+	bt_ctf_field_type_put(len_type);
+	return ret;
+}
+
 static int add_generic_values(struct ctf_writer *cw,
 			      struct bt_ctf_event *event,
 			      struct perf_evsel *evsel,
@@ -597,6 +675,12 @@ static int process_sample_event(struct perf_tool *tool,
 			return -1;
 	}
 
+	if (perf_evsel__is_bpf_output(evsel)) {
+		ret = add_bpf_output_values(event_class, event, sample);
+		if (ret)
+			return -1;
+	}
+
 	cs = ctf_stream(cw, get_sample_cpu(cw, sample, evsel));
 	if (cs) {
 		if (is_flush_needed(cs))
@@ -744,6 +828,25 @@ static int add_tracepoint_types(struct ctf_writer *cw,
 	return ret;
 }
 
+static int add_bpf_output_types(struct ctf_writer *cw,
+				struct bt_ctf_event_class *class)
+{
+	struct bt_ctf_field_type *len_type = cw->data.u32;
+	struct bt_ctf_field_type *seq_base_type = cw->data.u32_hex;
+	struct bt_ctf_field_type *seq_type;
+	int ret;
+
+	ret = bt_ctf_event_class_add_field(class, len_type, "raw_len");
+	if (ret)
+		return ret;
+
+	seq_type = bt_ctf_field_type_sequence_create(seq_base_type, "raw_len");
+	if (!seq_type)
+		return -1;
+
+	return bt_ctf_event_class_add_field(class, seq_type, "raw_data");
+}
+
 static int add_generic_types(struct ctf_writer *cw, struct perf_evsel *evsel,
 			     struct bt_ctf_event_class *event_class)
 {
@@ -755,7 +858,8 @@ static int add_generic_types(struct ctf_writer *cw, struct perf_evsel *evsel,
 	 *                              ctf event header
 	 *   PERF_SAMPLE_READ         - TODO
 	 *   PERF_SAMPLE_CALLCHAIN    - TODO
-	 *   PERF_SAMPLE_RAW          - tracepoint fields are handled separately
+	 *   PERF_SAMPLE_RAW          - tracepoint fields and BPF output
+	 *                              are handled separately
 	 *   PERF_SAMPLE_BRANCH_STACK - TODO
 	 *   PERF_SAMPLE_REGS_USER    - TODO
 	 *   PERF_SAMPLE_STACK_USER   - TODO
@@ -824,6 +928,12 @@ static int add_event(struct ctf_writer *cw, struct perf_evsel *evsel)
 			goto err;
 	}
 
+	if (perf_evsel__is_bpf_output(evsel)) {
+		ret = add_bpf_output_types(cw, event_class);
+		if (ret)
+			goto err;
+	}
+
 	ret = bt_ctf_stream_class_add_event_class(cw->stream_class, event_class);
 	if (ret) {
 		pr("Failed to add event class into stream.\n");
-- 
1.8.3.4

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#1343994 — [PATCH 10/46] perf core: Introduce new ioctl options to pause and resume ring buffer

Add new ioctl() to pause/resume ring-buffer output.

In some situations we want to read from ring buffer only when we
ensure nothing can write to the ring buffer during reading. Without
this patch we have to turn off all events attached to this ring buffer
to achieve this.

This patch is for supporting overwrite ring buffer. Following
commits will introduce new methods support reading from overwrite ring
buffer. Before reading caller must ensure the ring buffer is frozen, or
the reading is unreliable.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 include/uapi/linux/perf_event.h |  1 +
 kernel/events/core.c            | 13 +++++++++++++
 kernel/events/internal.h        | 11 +++++++++++
 kernel/events/ring_buffer.c     |  7 ++++++-
 4 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 1afe962..a3c1903 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -401,6 +401,7 @@ struct perf_event_attr {
 #define PERF_EVENT_IOC_SET_FILTER	_IOW('$', 6, char *)
 #define PERF_EVENT_IOC_ID		_IOR('$', 7, __u64 *)
 #define PERF_EVENT_IOC_SET_BPF		_IOW('$', 8, __u32)
+#define PERF_EVENT_IOC_PAUSE_OUTPUT	_IOW('$', 9, __u32)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 94c47e3..a7075ae 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4231,6 +4231,19 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
 	case PERF_EVENT_IOC_SET_BPF:
 		return perf_event_set_bpf_prog(event, arg);
 
+	case PERF_EVENT_IOC_PAUSE_OUTPUT: {
+		struct ring_buffer *rb;
+
+		rcu_read_lock();
+		rb = rcu_dereference(event->rb);
+		if (!event->rb) {
+			rcu_read_unlock();
+			return -EINVAL;
+		}
+		rb_toggle_paused(rb, !!arg);
+		rcu_read_unlock();
+		return 0;
+	}
 	default:
 		return -ENOTTY;
 	}
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 2bbad9c..6a93d1b 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -18,6 +18,7 @@ struct ring_buffer {
 #endif
 	int				nr_pages;	/* nr of data pages  */
 	int				overwrite;	/* can overwrite itself */
+	int				paused;		/* can write into ring buffer */
 
 	atomic_t			poll;		/* POLL_ for wakeups */
 
@@ -65,6 +66,16 @@ static inline void rb_free_rcu(struct rcu_head *rcu_head)
 	rb_free(rb);
 }
 
+static inline void
+rb_toggle_paused(struct ring_buffer *rb,
+		 bool pause)
+{
+	if (!pause && rb->nr_pages)
+		rb->paused = 0;
+	else
+		rb->paused = 1;
+}
+
 extern struct ring_buffer *
 rb_alloc(int nr_pages, long watermark, int cpu, int flags);
 extern void perf_event_wakeup(struct perf_event *event);
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 1faad2c..22e1a47 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -125,8 +125,11 @@ int perf_output_begin(struct perf_output_handle *handle,
 	if (unlikely(!rb))
 		goto out;
 
-	if (unlikely(!rb->nr_pages))
+	if (unlikely(rb->paused)) {
+		if (rb->nr_pages)
+			local_inc(&rb->lost);
 		goto out;
+	}
 
 	handle->rb    = rb;
 	handle->event = event;
@@ -244,6 +247,8 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
 	INIT_LIST_HEAD(&rb->event_list);
 	spin_lock_init(&rb->event_lock);
 	init_irq_work(&rb->irq_work, rb_irq_work);
+
+	rb->paused = rb->nr_pages ? 0 : 1;
 }
 
 static void ring_buffer_put_async(struct ring_buffer *rb)
-- 
1.8.3.4

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#1345915 — Re: [PATCH 10/46] perf core: Introduce new ioctl options to pause and resume ring buffer

Em Fri, Feb 26, 2016 at 09:31:58AM +0000, Wang Nan escreveu:
> Add new ioctl() to pause/resume ring-buffer output.
> 
> In some situations we want to read from ring buffer only when we
> ensure nothing can write to the ring buffer during reading. Without
> this patch we have to turn off all events attached to this ring buffer
> to achieve this.
> 
> This patch is for supporting overwrite ring buffer. Following
> commits will introduce new methods support reading from overwrite ring
> buffer. Before reading caller must ensure the ring buffer is frozen, or
> the reading is unreliable.

Peter, have you have the chance too look at this and the other kernel
bits in this kit?

- Arnaldo
 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: He Kuang <hekuang@huawei.com>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Zefan Li <lizefan@huawei.com>
> Cc: pi3orama@163.com
> ---
>  include/uapi/linux/perf_event.h |  1 +
>  kernel/events/core.c            | 13 +++++++++++++
>  kernel/events/internal.h        | 11 +++++++++++
>  kernel/events/ring_buffer.c     |  7 ++++++-
>  4 files changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 1afe962..a3c1903 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -401,6 +401,7 @@ struct perf_event_attr {
>  #define PERF_EVENT_IOC_SET_FILTER	_IOW('$', 6, char *)
>  #define PERF_EVENT_IOC_ID		_IOR('$', 7, __u64 *)
>  #define PERF_EVENT_IOC_SET_BPF		_IOW('$', 8, __u32)
> +#define PERF_EVENT_IOC_PAUSE_OUTPUT	_IOW('$', 9, __u32)
>  
>  enum perf_event_ioc_flags {
>  	PERF_IOC_FLAG_GROUP		= 1U << 0,
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 94c47e3..a7075ae 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -4231,6 +4231,19 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
>  	case PERF_EVENT_IOC_SET_BPF:
>  		return perf_event_set_bpf_prog(event, arg);
>  
> +	case PERF_EVENT_IOC_PAUSE_OUTPUT: {
> +		struct ring_buffer *rb;
> +
> +		rcu_read_lock();
> +		rb = rcu_dereference(event->rb);
> +		if (!event->rb) {
> +			rcu_read_unlock();
> +			return -EINVAL;
> +		}
> +		rb_toggle_paused(rb, !!arg);
> +		rcu_read_unlock();
> +		return 0;
> +	}
>  	default:
>  		return -ENOTTY;
>  	}
> diff --git a/kernel/events/internal.h b/kernel/events/internal.h
> index 2bbad9c..6a93d1b 100644
> --- a/kernel/events/internal.h
> +++ b/kernel/events/internal.h
> @@ -18,6 +18,7 @@ struct ring_buffer {
>  #endif
>  	int				nr_pages;	/* nr of data pages  */
>  	int				overwrite;	/* can overwrite itself */
> +	int				paused;		/* can write into ring buffer */
>  
>  	atomic_t			poll;		/* POLL_ for wakeups */
>  
> @@ -65,6 +66,16 @@ static inline void rb_free_rcu(struct rcu_head *rcu_head)
>  	rb_free(rb);
>  }
>  
> +static inline void
> +rb_toggle_paused(struct ring_buffer *rb,
> +		 bool pause)
> +{
> +	if (!pause && rb->nr_pages)
> +		rb->paused = 0;
> +	else
> +		rb->paused = 1;
> +}
> +
>  extern struct ring_buffer *
>  rb_alloc(int nr_pages, long watermark, int cpu, int flags);
>  extern void perf_event_wakeup(struct perf_event *event);
> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> index 1faad2c..22e1a47 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -125,8 +125,11 @@ int perf_output_begin(struct perf_output_handle *handle,
>  	if (unlikely(!rb))
>  		goto out;
>  
> -	if (unlikely(!rb->nr_pages))
> +	if (unlikely(rb->paused)) {
> +		if (rb->nr_pages)
> +			local_inc(&rb->lost);
>  		goto out;
> +	}
>  
>  	handle->rb    = rb;
>  	handle->event = event;
> @@ -244,6 +247,8 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
>  	INIT_LIST_HEAD(&rb->event_list);
>  	spin_lock_init(&rb->event_lock);
>  	init_irq_work(&rb->irq_work, rb_irq_work);
> +
> +	rb->paused = rb->nr_pages ? 0 : 1;
>  }
>  
>  static void ring_buffer_put_async(struct ring_buffer *rb)
> -- 
> 1.8.3.4

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#1348696 — Re: [PATCH 10/46] perf core: Introduce new ioctl options to pause and resume ring buffer

Hi Peter,

  Patch 10/46 to 14/46 were sent separately to you and modified
follow your suggestion. Do you have further comment on it?

Thank you.

On 2016/2/29 23:39, Arnaldo Carvalho de Melo wrote:
> Em Fri, Feb 26, 2016 at 09:31:58AM +0000, Wang Nan escreveu:
>> Add new ioctl() to pause/resume ring-buffer output.
>>
>> In some situations we want to read from ring buffer only when we
>> ensure nothing can write to the ring buffer during reading. Without
>> this patch we have to turn off all events attached to this ring buffer
>> to achieve this.
>>
>> This patch is for supporting overwrite ring buffer. Following
>> commits will introduce new methods support reading from overwrite ring
>> buffer. Before reading caller must ensure the ring buffer is frozen, or
>> the reading is unreliable.
> Peter, have you have the chance too look at this and the other kernel
> bits in this kit?
>
> - Arnaldo
>   
>> Signed-off-by: Wang Nan <wangnan0@huawei.com>
>> Cc: He Kuang <hekuang@huawei.com>
>> Cc: Alexei Starovoitov <ast@kernel.org>
>> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
>> Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
>> Cc: Jiri Olsa <jolsa@kernel.org>
>> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> Cc: Namhyung Kim <namhyung@kernel.org>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Zefan Li <lizefan@huawei.com>
>> Cc: pi3orama@163.com
>> ---
>>   include/uapi/linux/perf_event.h |  1 +
>>   kernel/events/core.c            | 13 +++++++++++++
>>   kernel/events/internal.h        | 11 +++++++++++
>>   kernel/events/ring_buffer.c     |  7 ++++++-
>>   4 files changed, 31 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
>> index 1afe962..a3c1903 100644
>> --- a/include/uapi/linux/perf_event.h
>> +++ b/include/uapi/linux/perf_event.h
>> @@ -401,6 +401,7 @@ struct perf_event_attr {
>>   #define PERF_EVENT_IOC_SET_FILTER	_IOW('$', 6, char *)
>>   #define PERF_EVENT_IOC_ID		_IOR('$', 7, __u64 *)
>>   #define PERF_EVENT_IOC_SET_BPF		_IOW('$', 8, __u32)
>> +#define PERF_EVENT_IOC_PAUSE_OUTPUT	_IOW('$', 9, __u32)
>>   
>>   enum perf_event_ioc_flags {
>>   	PERF_IOC_FLAG_GROUP		= 1U << 0,
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 94c47e3..a7075ae 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -4231,6 +4231,19 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
>>   	case PERF_EVENT_IOC_SET_BPF:
>>   		return perf_event_set_bpf_prog(event, arg);
>>   
>> +	case PERF_EVENT_IOC_PAUSE_OUTPUT: {
>> +		struct ring_buffer *rb;
>> +
>> +		rcu_read_lock();
>> +		rb = rcu_dereference(event->rb);
>> +		if (!event->rb) {
>> +			rcu_read_unlock();
>> +			return -EINVAL;
>> +		}
>> +		rb_toggle_paused(rb, !!arg);
>> +		rcu_read_unlock();
>> +		return 0;
>> +	}
>>   	default:
>>   		return -ENOTTY;
>>   	}
>> diff --git a/kernel/events/internal.h b/kernel/events/internal.h
>> index 2bbad9c..6a93d1b 100644
>> --- a/kernel/events/internal.h
>> +++ b/kernel/events/internal.h
>> @@ -18,6 +18,7 @@ struct ring_buffer {
>>   #endif
>>   	int				nr_pages;	/* nr of data pages  */
>>   	int				overwrite;	/* can overwrite itself */
>> +	int				paused;		/* can write into ring buffer */
>>   
>>   	atomic_t			poll;		/* POLL_ for wakeups */
>>   
>> @@ -65,6 +66,16 @@ static inline void rb_free_rcu(struct rcu_head *rcu_head)
>>   	rb_free(rb);
>>   }
>>   
>> +static inline void
>> +rb_toggle_paused(struct ring_buffer *rb,
>> +		 bool pause)
>> +{
>> +	if (!pause && rb->nr_pages)
>> +		rb->paused = 0;
>> +	else
>> +		rb->paused = 1;
>> +}
>> +
>>   extern struct ring_buffer *
>>   rb_alloc(int nr_pages, long watermark, int cpu, int flags);
>>   extern void perf_event_wakeup(struct perf_event *event);
>> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
>> index 1faad2c..22e1a47 100644
>> --- a/kernel/events/ring_buffer.c
>> +++ b/kernel/events/ring_buffer.c
>> @@ -125,8 +125,11 @@ int perf_output_begin(struct perf_output_handle *handle,
>>   	if (unlikely(!rb))
>>   		goto out;
>>   
>> -	if (unlikely(!rb->nr_pages))
>> +	if (unlikely(rb->paused)) {
>> +		if (rb->nr_pages)
>> +			local_inc(&rb->lost);
>>   		goto out;
>> +	}
>>   
>>   	handle->rb    = rb;
>>   	handle->event = event;
>> @@ -244,6 +247,8 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
>>   	INIT_LIST_HEAD(&rb->event_list);
>>   	spin_lock_init(&rb->event_lock);
>>   	init_irq_work(&rb->irq_work, rb_irq_work);
>> +
>> +	rb->paused = rb->nr_pages ? 0 : 1;
>>   }
>>   
>>   static void ring_buffer_put_async(struct ring_buffer *rb)
>> -- 
>> 1.8.3.4

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#1343995 — [PATCH 09/46] perf data: Explicitly set byte order for integer types

After babeltrace commit 5cec03e402aa ("ir: copy variants and
sequences when setting a field path"), 'perf data convert' gets
incorrect result if there's bpf output data. For example:

 # perf data convert --to-ctf ./out.ctf
 # babeltrace ./out.ctf
 [10:44:31.186045346] (+?.?????????) evt: { cpu_id = 0 }, { perf_ip = 0xFFFFFFFF810E7DD1, perf_tid = 23819, perf_pid = 23819, perf_id = 518, raw_len = 3, raw_data = [ [0] = 0xC028E32F, [1] = 0x815D0100, [2] = 0x1000000 ] }
 [10:44:31.286101003] (+0.100055657) evt: { cpu_id = 0 }, { perf_ip = 0xFFFFFFFF8105B609, perf_tid = 23819, perf_pid = 23819, perf_id = 518, raw_len = 3, raw_data = [ [0] = 0x35D9F1EB, [1] = 0x15D81, [2] = 0x2 ] }

The expected result of the first sample should be:

 raw_data = [ [0] = 0x2FE328C0, [1] = 0x15D81, [2] = 0x1 ] }

however, 'perf data convert' output big endian value to resuling CTF
file.

The reason is a internal change (or a bug?) of babeltrace.

Before this patch, at the first add_bpf_output_values(), byte order of
all integer type is uncertain (is 0, neither 1234 (le) nor 4321 (be)).
It would be fixed by:

perf_evlist__deliver_sample
 -> process_sample_event
   -> ctf_stream
      ...
      ->bt_ctf_trace_add_stream_class
        ->bt_ctf_field_type_structure_set_byte_order
          ->bt_ctf_field_type_integer_set_byte_order

during creating the stream.

However, the babeltrace commit mentioned above duplicates types in
sequence to prevent potential conflict in following call stack and
link the newly allocated type into the 'raw_data' sequence:

perf_evlist__deliver_sample
 -> process_sample_event
   -> ctf_stream
      ...
      -> bt_ctf_trace_add_stream_class
        -> bt_ctf_stream_class_resolve_types
           ...
           -> bt_ctf_field_type_sequence_copy
             ->bt_ctf_field_type_integer_copy

This happens before byte order setting, so only the newly allocated
type is initialized, the byte order of original type perf choose to
create the first raw_data is still uncertain.

Byte order in CTF output is not related to byte order in perf.data.
Setting it to anything other than BT_CTF_BYTE_ORDER_NATIVE solves this
problem (only BT_CTF_BYTE_ORDER_NATIVE needs to be fixed). To reduce
behavior changing, set byte order according to compiling options.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/util/data-convert-bt.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
index 1f608a6..811af89 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/tools/perf/util/data-convert-bt.c
@@ -1080,6 +1080,12 @@ static struct bt_ctf_field_type *create_int_type(int size, bool sign, bool hex)
 	    bt_ctf_field_type_integer_set_base(type, BT_CTF_INTEGER_BASE_HEXADECIMAL))
 		goto err;
 
+#if __BYTE_ORDER == __BIG_ENDIAN
+	bt_ctf_field_type_set_byte_order(type, BT_CTF_BYTE_ORDER_BIG_ENDIAN);
+#else
+	bt_ctf_field_type_set_byte_order(type, BT_CTF_BYTE_ORDER_LITTLE_ENDIAN);
+#endif
+
 	pr2("Created type: INTEGER %d-bit %ssigned %s\n",
 	    size, sign ? "un" : "", hex ? "hex" : "");
 	return type;
-- 
1.8.3.4

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#1343996 — [PATCH 03/46] perf config: Bring perf_default_config to the very beginning at main()

Before this patch each subcommand calls perf_config() by themselvs, set
default configuration together with subcommand specific options. If a
subcommand doesn't have it own options, it needs to call
'perf_config(perf_default_config, NULL)' to ensure .perfconfig is
loaded.

This patch brings perf_config(perf_default_config, NULL) to the
very beginning of main(), so subcommand don't need to consider
default options.

After this patch, 'llvm.clang-path' works for 'perf trace'.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/builtin-diff.c          | 2 --
 tools/perf/builtin-help.c          | 2 +-
 tools/perf/builtin-kmem.c          | 4 ++--
 tools/perf/builtin-report.c        | 2 +-
 tools/perf/builtin-top.c           | 4 ++--
 tools/perf/perf.c                  | 2 ++
 tools/perf/tests/llvm.c            | 8 --------
 tools/perf/util/color.c            | 5 +++--
 tools/perf/util/data-convert-bt.c  | 2 +-
 tools/perf/util/help-unknown-cmd.c | 5 +++--
 10 files changed, 15 insertions(+), 21 deletions(-)

diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index 36ccc2b..4d72359 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -1264,8 +1264,6 @@ int cmd_diff(int argc, const char **argv, const char *prefix __maybe_unused)
 	if (ret < 0)
 		return ret;
 
-	perf_config(perf_default_config, NULL);
-
 	argc = parse_options(argc, argv, options, diff_usage, 0);
 
 	if (symbol__init(NULL) < 0)
diff --git a/tools/perf/builtin-help.c b/tools/perf/builtin-help.c
index f4dd2b4..49d55e2 100644
--- a/tools/perf/builtin-help.c
+++ b/tools/perf/builtin-help.c
@@ -272,7 +272,7 @@ static int perf_help_config(const char *var, const char *value, void *cb)
 	if (!prefixcmp(var, "man."))
 		return add_man_viewer_info(var, value);
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static struct cmdnames main_cmds, other_cmds;
diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c
index 1180105..4d3340c 100644
--- a/tools/perf/builtin-kmem.c
+++ b/tools/perf/builtin-kmem.c
@@ -1834,7 +1834,7 @@ static int __cmd_record(int argc, const char **argv)
 	return cmd_record(i, rec_argv, NULL);
 }
 
-static int kmem_config(const char *var, const char *value, void *cb)
+static int kmem_config(const char *var, const char *value, void *cb __maybe_unused)
 {
 	if (!strcmp(var, "kmem.default")) {
 		if (!strcmp(value, "slab"))
@@ -1847,7 +1847,7 @@ static int kmem_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 int cmd_kmem(int argc, const char **argv, const char *prefix __maybe_unused)
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index f4d8244..7eea49f 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -90,7 +90,7 @@ static int report__config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static int hist_iter__report_callback(struct hist_entry_iter *iter,
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index b86b623..94af190 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1065,7 +1065,7 @@ parse_callchain_opt(const struct option *opt, const char *arg, int unset)
 	return parse_callchain_top_opt(arg);
 }
 
-static int perf_top_config(const char *var, const char *value, void *cb)
+static int perf_top_config(const char *var, const char *value, void *cb __maybe_unused)
 {
 	if (!strcmp(var, "top.call-graph"))
 		var = "call-graph.record-mode"; /* fall-through */
@@ -1074,7 +1074,7 @@ static int perf_top_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static int
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index f6321194..aaee0a7 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -548,6 +548,8 @@ int main(int argc, const char **argv)
 
 	srandom(time(NULL));
 
+	perf_config(perf_default_config, NULL);
+
 	/* get debugfs/tracefs mount point from /proc/mounts */
 	tracing_path_mount();
 
diff --git a/tools/perf/tests/llvm.c b/tools/perf/tests/llvm.c
index 70edcdf..cff564f 100644
--- a/tools/perf/tests/llvm.c
+++ b/tools/perf/tests/llvm.c
@@ -6,12 +6,6 @@
 #include "tests.h"
 #include "debug.h"
 
-static int perf_config_cb(const char *var, const char *val,
-			  void *arg __maybe_unused)
-{
-	return perf_default_config(var, val, arg);
-}
-
 #ifdef HAVE_LIBBPF_SUPPORT
 static int test__bpf_parsing(void *obj_buf, size_t obj_buf_sz)
 {
@@ -77,8 +71,6 @@ test_llvm__fetch_bpf_obj(void **p_obj_buf,
 	if (should_load_fail)
 		*should_load_fail = bpf_source_table[idx].should_load_fail;
 
-	perf_config(perf_config_cb, NULL);
-
 	/*
 	 * Skip this test if user's .perfconfig doesn't set [llvm] section
 	 * and clang is not found in $PATH, and this is not perf test -v
diff --git a/tools/perf/util/color.c b/tools/perf/util/color.c
index e5fb88b..43e84aa 100644
--- a/tools/perf/util/color.c
+++ b/tools/perf/util/color.c
@@ -32,14 +32,15 @@ int perf_config_colorbool(const char *var, const char *value, int stdout_is_tty)
 	return 0;
 }
 
-int perf_color_default_config(const char *var, const char *value, void *cb)
+int perf_color_default_config(const char *var, const char *value,
+			      void *cb __maybe_unused)
 {
 	if (!strcmp(var, "color.ui")) {
 		perf_use_color_default = perf_config_colorbool(var, value, -1);
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static int __color_vsnprintf(char *bf, size_t size, const char *color,
diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
index b722e57..6729f4d 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/tools/perf/util/data-convert-bt.c
@@ -1117,7 +1117,7 @@ static int convert__config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 int bt_convert__perf2ctf(const char *input, const char *path, bool force)
diff --git a/tools/perf/util/help-unknown-cmd.c b/tools/perf/util/help-unknown-cmd.c
index dc1e41c..43a98a4 100644
--- a/tools/perf/util/help-unknown-cmd.c
+++ b/tools/perf/util/help-unknown-cmd.c
@@ -6,7 +6,8 @@
 static int autocorrect;
 static struct cmdnames aliases;
 
-static int perf_unknown_cmd_config(const char *var, const char *value, void *cb)
+static int perf_unknown_cmd_config(const char *var, const char *value,
+				   void *cb __maybe_unused)
 {
 	if (!strcmp(var, "help.autocorrect"))
 		autocorrect = perf_config_int(var,value);
@@ -14,7 +15,7 @@ static int perf_unknown_cmd_config(const char *var, const char *value, void *cb)
 	if (!prefixcmp(var, "alias."))
 		add_cmdname(&aliases, var + 6, strlen(var + 6));
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static int levenshtein_compare(const void *p1, const void *p2)
-- 
1.8.3.4

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#1344963 — [tip:perf/core] perf config: Bring perf_default_config to the very beginning at main()

Commit-ID:  b8cbb349061edda648463b086cfa869a7ab583af
Gitweb:     http://git.kernel.org/tip/b8cbb349061edda648463b086cfa869a7ab583af
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Fri, 26 Feb 2016 09:31:51 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 26 Feb 2016 19:49:16 -0300

perf config: Bring perf_default_config to the very beginning at main()

Before this patch each subcommand calls perf_config() by themself,
reading the default configuration together with subcommand specific
options. If a subcommand doesn't have it own options, it needs to call
'perf_config(perf_default_config, NULL)' to ensure .perfconfig is
loaded.

This patch brings perf_config(perf_default_config, NULL) to the very
start of main(), so subcommands don't need to do it.

After this patch, 'llvm.clang-path' works for 'perf trace'.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Suggested-and-Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1456479154-136027-4-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/builtin-diff.c          | 2 --
 tools/perf/builtin-help.c          | 2 +-
 tools/perf/builtin-kmem.c          | 4 ++--
 tools/perf/builtin-report.c        | 2 +-
 tools/perf/builtin-top.c           | 4 ++--
 tools/perf/perf.c                  | 2 ++
 tools/perf/tests/llvm.c            | 8 --------
 tools/perf/util/color.c            | 5 +++--
 tools/perf/util/data-convert-bt.c  | 2 +-
 tools/perf/util/help-unknown-cmd.c | 5 +++--
 10 files changed, 15 insertions(+), 21 deletions(-)

diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index 36ccc2b..4d72359 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -1264,8 +1264,6 @@ int cmd_diff(int argc, const char **argv, const char *prefix __maybe_unused)
 	if (ret < 0)
 		return ret;
 
-	perf_config(perf_default_config, NULL);
-
 	argc = parse_options(argc, argv, options, diff_usage, 0);
 
 	if (symbol__init(NULL) < 0)
diff --git a/tools/perf/builtin-help.c b/tools/perf/builtin-help.c
index f4dd2b4..49d55e2 100644
--- a/tools/perf/builtin-help.c
+++ b/tools/perf/builtin-help.c
@@ -272,7 +272,7 @@ static int perf_help_config(const char *var, const char *value, void *cb)
 	if (!prefixcmp(var, "man."))
 		return add_man_viewer_info(var, value);
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static struct cmdnames main_cmds, other_cmds;
diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c
index 1180105..4d3340c 100644
--- a/tools/perf/builtin-kmem.c
+++ b/tools/perf/builtin-kmem.c
@@ -1834,7 +1834,7 @@ static int __cmd_record(int argc, const char **argv)
 	return cmd_record(i, rec_argv, NULL);
 }
 
-static int kmem_config(const char *var, const char *value, void *cb)
+static int kmem_config(const char *var, const char *value, void *cb __maybe_unused)
 {
 	if (!strcmp(var, "kmem.default")) {
 		if (!strcmp(value, "slab"))
@@ -1847,7 +1847,7 @@ static int kmem_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 int cmd_kmem(int argc, const char **argv, const char *prefix __maybe_unused)
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index f4d8244..7eea49f 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -90,7 +90,7 @@ static int report__config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static int hist_iter__report_callback(struct hist_entry_iter *iter,
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index b86b623..94af190 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1065,7 +1065,7 @@ parse_callchain_opt(const struct option *opt, const char *arg, int unset)
 	return parse_callchain_top_opt(arg);
 }
 
-static int perf_top_config(const char *var, const char *value, void *cb)
+static int perf_top_config(const char *var, const char *value, void *cb __maybe_unused)
 {
 	if (!strcmp(var, "top.call-graph"))
 		var = "call-graph.record-mode"; /* fall-through */
@@ -1074,7 +1074,7 @@ static int perf_top_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static int
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index f632119..aaee0a7 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -548,6 +548,8 @@ int main(int argc, const char **argv)
 
 	srandom(time(NULL));
 
+	perf_config(perf_default_config, NULL);
+
 	/* get debugfs/tracefs mount point from /proc/mounts */
 	tracing_path_mount();
 
diff --git a/tools/perf/tests/llvm.c b/tools/perf/tests/llvm.c
index 70edcdf..cff564f 100644
--- a/tools/perf/tests/llvm.c
+++ b/tools/perf/tests/llvm.c
@@ -6,12 +6,6 @@
 #include "tests.h"
 #include "debug.h"
 
-static int perf_config_cb(const char *var, const char *val,
-			  void *arg __maybe_unused)
-{
-	return perf_default_config(var, val, arg);
-}
-
 #ifdef HAVE_LIBBPF_SUPPORT
 static int test__bpf_parsing(void *obj_buf, size_t obj_buf_sz)
 {
@@ -77,8 +71,6 @@ test_llvm__fetch_bpf_obj(void **p_obj_buf,
 	if (should_load_fail)
 		*should_load_fail = bpf_source_table[idx].should_load_fail;
 
-	perf_config(perf_config_cb, NULL);
-
 	/*
 	 * Skip this test if user's .perfconfig doesn't set [llvm] section
 	 * and clang is not found in $PATH, and this is not perf test -v
diff --git a/tools/perf/util/color.c b/tools/perf/util/color.c
index e5fb88b..43e84aa 100644
--- a/tools/perf/util/color.c
+++ b/tools/perf/util/color.c
@@ -32,14 +32,15 @@ int perf_config_colorbool(const char *var, const char *value, int stdout_is_tty)
 	return 0;
 }
 
-int perf_color_default_config(const char *var, const char *value, void *cb)
+int perf_color_default_config(const char *var, const char *value,
+			      void *cb __maybe_unused)
 {
 	if (!strcmp(var, "color.ui")) {
 		perf_use_color_default = perf_config_colorbool(var, value, -1);
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static int __color_vsnprintf(char *bf, size_t size, const char *color,
diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
index b722e57..6729f4d 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/tools/perf/util/data-convert-bt.c
@@ -1117,7 +1117,7 @@ static int convert__config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 int bt_convert__perf2ctf(const char *input, const char *path, bool force)
diff --git a/tools/perf/util/help-unknown-cmd.c b/tools/perf/util/help-unknown-cmd.c
index dc1e41c..43a98a4 100644
--- a/tools/perf/util/help-unknown-cmd.c
+++ b/tools/perf/util/help-unknown-cmd.c
@@ -6,7 +6,8 @@
 static int autocorrect;
 static struct cmdnames aliases;
 
-static int perf_unknown_cmd_config(const char *var, const char *value, void *cb)
+static int perf_unknown_cmd_config(const char *var, const char *value,
+				   void *cb __maybe_unused)
 {
 	if (!strcmp(var, "help.autocorrect"))
 		autocorrect = perf_config_int(var,value);
@@ -14,7 +15,7 @@ static int perf_unknown_cmd_config(const char *var, const char *value, void *cb)
 	if (!prefixcmp(var, "alias."))
 		add_cmdname(&aliases, var + 6, strlen(var + 6));
 
-	return perf_default_config(var, value, cb);
+	return 0;
 }
 
 static int levenshtein_compare(const void *p1, const void *p2)

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