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[PATCH 2/5] perf tools: Extract __perf_evlist__mmap_read()

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  [PATCH 2/5] perf tools: Extract __perf_evlist__mmap_read() Wang Nan <wangnan0@huawei.com> - 2016-04-26 04:40 +0200
    Re: [PATCH 2/5] perf tools: Extract __perf_evlist__mmap_read() Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-04-26 15:40 +0200

#1387097 — [PATCH 2/5] perf tools: Extract __perf_evlist__mmap_read()

Extract event reader to __perf_evlist__mmap_read(). Future commit will
feed it with manually computed 'head' and 'old' pointers.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/util/evlist.c | 40 +++++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 85271e5..3ee94b2 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -679,24 +679,15 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
 	return NULL;
 }
 
-union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+static union perf_event *
+__perf_evlist__mmap_read(struct perf_mmap *md, bool overwrite, u64 head,
+			 u64 old, u64 *prev)
 {
-	struct perf_mmap *md = &evlist->mmap[idx];
-	u64 head;
-	u64 old = md->prev;
-	int diff;
 	unsigned char *data = md->base + page_size;
 	union perf_event *event = NULL;
+	int diff = head - old;
 
-	/*
-	 * Check if event was unmapped due to a POLLHUP/POLLERR.
-	 */
-	if (!atomic_read(&md->refcnt))
-		return NULL;
-
-	head = perf_mmap__read_head(md);
-	diff = head - old;
-	if (evlist->overwrite) {
+	if (overwrite) {
 		/*
 		 * If we're further behind than half the buffer, there's a chance
 		 * the writer will bite our tail and mess up the samples under us.
@@ -751,11 +742,30 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
 	}
 
 broken_event:
-	md->prev = old;
+	if (prev)
+		*prev = old;
 
 	return event;
 }
 
+union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+{
+	struct perf_mmap *md = &evlist->mmap[idx];
+	u64 head;
+	u64 old = md->prev;
+
+	/*
+	 * Check if event was unmapped due to a POLLHUP/POLLERR.
+	 */
+	if (!atomic_read(&md->refcnt))
+		return NULL;
+
+	head = perf_mmap__read_head(md);
+
+	return __perf_evlist__mmap_read(md, evlist->overwrite, head,
+					old, &md->prev);
+}
+
 static bool perf_mmap__empty(struct perf_mmap *md)
 {
 	return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;
-- 
1.8.3.4

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#1387474

Em Tue, Apr 26, 2016 at 02:28:55AM +0000, Wang Nan escreveu:
> Extract event reader to __perf_evlist__mmap_read(). Future commit will
> feed it with manually computed 'head' and 'old' pointers.
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Zefan Li <lizefan@huawei.com>
> Cc: pi3orama@163.com
> ---
>  tools/perf/util/evlist.c | 40 +++++++++++++++++++++++++---------------
>  1 file changed, 25 insertions(+), 15 deletions(-)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 85271e5..3ee94b2 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -679,24 +679,15 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
>  	return NULL;
>  }
>  
> -union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
> +static union perf_event *
> +__perf_evlist__mmap_read(struct perf_mmap *md, bool overwrite, u64 head,
> +			 u64 old, u64 *prev)
>  {

Ok, now this is not a perf_evlist method anymore, see the first
parameter? It handles perf_mmap instances, so please rename it to:

static union perf_event *perf_mmap__read(struct perf_mmap *md, bool overwrite,
					 u64 head, u64 *prev)

And thanks for leaving the renaming of those variables to the next
patch, that eases reviewieng indeed.

> -	struct perf_mmap *md = &evlist->mmap[idx];
> -	u64 head;
> -	u64 old = md->prev;
>  
> +union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
> +{
> +	struct perf_mmap *md = &evlist->mmap[idx];
> +	u64 head;
> +	u64 old = md->prev;
> +
> +	if (!atomic_read(&md->refcnt))
> +		return NULL;
> +
> +	head = perf_mmap__read_head(md);
> +
> +	return __perf_evlist__mmap_read(md, evlist->overwrite, head,
> +					old, &md->prev);


See that perf_mmap__read_head()? It acts on a struct perf_mmap too, thus
the prefix. This will end up as:

	head = perf_mmap__read_head(md);

	return perf_mmap__read(md, evlist->overwrite, head, old, &md->prev);

And see below yet another perf_mmap method, perf_mmap__empty()

Regards,

- Arnaldo
> +}
> +
>  static bool perf_mmap__empty(struct perf_mmap *md)
>  {
>  	return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;
> -- 
> 1.8.3.4

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