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[RFC V3] Add gup trace points support

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  [RFC V3] Add gup trace points support Yang Shi <yang.shi@linaro.org> - 2015-12-08 21:10 +0100
    [PATCH v3 2/7] mm/gup: add gup trace points Yang Shi <yang.shi@linaro.org> - 2015-12-08 21:10 +0100
      Re: [PATCH v3 2/7] mm/gup: add gup trace points Steven Rostedt <rostedt@goodmis.org> - 2015-12-08 21:30 +0100
        Re: [PATCH v3 2/7] mm/gup: add gup trace points "Shi, Yang" <yang.shi@linaro.org> - 2015-12-08 22:00 +0100
    [PATCH v3 3/7] x86: mm/gup: add gup trace points Yang Shi <yang.shi@linaro.org> - 2015-12-08 21:10 +0100
    [PATCH v3 5/7] s390: mm/gup: add gup trace points Yang Shi <yang.shi@linaro.org> - 2015-12-08 21:10 +0100
    [PATCH v3 4/7] mips: mm/gup: add gup trace points Yang Shi <yang.shi@linaro.org> - 2015-12-08 21:10 +0100

#1286811 — [RFC V3] Add gup trace points support

v3:
* Adopted suggestion from Dave Hansen to move the gup header include to the last
* Adopted comments from Steven:
  - Use DECLARE_EVENT_CLASS and DEFINE_EVENT
  - Just keep necessary TP_ARGS
* Moved archtichture specific fall-backable fast version trace point after the
  do while loop since it may jump to the slow version.
* Not implement recording return value since Steven plans to have it in generic
  tracing code
 
v2:
* Adopted commetns from Steven
  - remove all reference to tsk->comm since it is unnecessary for non-sched
    trace points
  - reduce arguments for __get_user_pages trace point and update mm/gup.c
    accordingly
* Added Ralf's acked-by for patch 4/7.

There is not content change for the trace points in arch specific mm/gup.c.


Some background about why I think this might be useful.

When I was profiling some hugetlb related program, I got page-faults event
doubled when hugetlb is enabled. When I looked into the code, I found page-faults
come from two places, do_page_fault and gup. So, I tried to figure out which
play a role (or both) in my use case. But I can't find existing finer tracing
event for sub page-faults in current mainline kernel.

So, I added the gup trace points support to have finer tracing events for
page-faults. The below events are added:

__get_user_pages
__get_user_pages_fast
fixup_user_fault

Both __get_user_pages and fixup_user_fault call handle_mm_fault.

Just added trace points to raw version __get_user_pages since all variants
will call it finally to do real work.

Although __get_user_pages_fast doesn't call handle_mm_fault, it might be useful
to have it to distinguish between slow and fast version.

Yang Shi (7):
      trace/events: Add gup trace events
      mm/gup: add gup trace points
      x86: mm/gup: add gup trace points
      mips: mm/gup: add gup trace points
      s390: mm/gup: add gup trace points
      sh: mm/gup: add gup trace points
      sparc64: mm/gup: add gup trace points

 arch/mips/mm/gup.c         |  7 +++++++
 arch/s390/mm/gup.c         |  6 ++++++
 arch/sh/mm/gup.c           |  7 +++++++
 arch/sparc/mm/gup.c        |  7 +++++++
 arch/x86/mm/gup.c          |  7 +++++++
 include/trace/events/gup.h | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 mm/gup.c                   |  8 ++++++++
 7 files changed, 105 insertions(+)
 create mode 100644 include/trace/events/gup.h
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#1286812 — [PATCH v3 2/7] mm/gup: add gup trace points

For slow version, just add trace point for raw __get_user_pages since all
slow variants call it to do the real work finally.

Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
 mm/gup.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/gup.c b/mm/gup.c
index deafa2c..44f05c9 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -18,6 +18,9 @@
 
 #include "internal.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/gup.h>
+
 static struct page *no_page_table(struct vm_area_struct *vma,
 		unsigned int flags)
 {
@@ -462,6 +465,8 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 	if (!nr_pages)
 		return 0;
 
+	trace_gup_get_user_pages(start, nr_pages);
+
 	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
 
 	/*
@@ -599,6 +604,7 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
 	if (!(vm_flags & vma->vm_flags))
 		return -EFAULT;
 
+	trace_gup_fixup_user_fault(address);
 	ret = handle_mm_fault(mm, vma, address, fault_flags);
 	if (ret & VM_FAULT_ERROR) {
 		if (ret & VM_FAULT_OOM)
@@ -1340,6 +1346,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 					start, len)))
 		return 0;
 
+	trace_gup_get_user_pages_fast(start, (unsigned long) nr_pages);
+
 	/*
 	 * Disable interrupts.  We use the nested form as we can already have
 	 * interrupts disabled by get_futex_key.
-- 
2.0.2

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#1286825 — Re: [PATCH v3 2/7] mm/gup: add gup trace points

On Tue,  8 Dec 2015 11:39:50 -0800
Yang Shi <yang.shi@linaro.org> wrote:

> For slow version, just add trace point for raw __get_user_pages since all
> slow variants call it to do the real work finally.
> 
> Signed-off-by: Yang Shi <yang.shi@linaro.org>
> ---
>  mm/gup.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index deafa2c..44f05c9 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -18,6 +18,9 @@
>  
>  #include "internal.h"
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/gup.h>
> +
>  static struct page *no_page_table(struct vm_area_struct *vma,
>  		unsigned int flags)
>  {
> @@ -462,6 +465,8 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
>  	if (!nr_pages)
>  		return 0;
>  
> +	trace_gup_get_user_pages(start, nr_pages);
> +
>  	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
>  
>  	/*
> @@ -599,6 +604,7 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
>  	if (!(vm_flags & vma->vm_flags))
>  		return -EFAULT;
>  
> +	trace_gup_fixup_user_fault(address);
>  	ret = handle_mm_fault(mm, vma, address, fault_flags);
>  	if (ret & VM_FAULT_ERROR) {
>  		if (ret & VM_FAULT_OOM)
> @@ -1340,6 +1346,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
>  					start, len)))
>  		return 0;
>  
> +	trace_gup_get_user_pages_fast(start, (unsigned long) nr_pages);

typecast shouldn't be needed. But I'm wondering, it would save space in
the ring buffer if we used unsigend int instead of long. Will nr_pages
ever be bigger than 4 billion?

-- Steve

> +
>  	/*
>  	 * Disable interrupts.  We use the nested form as we can already have
>  	 * interrupts disabled by get_futex_key.

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#1286847 — Re: [PATCH v3 2/7] mm/gup: add gup trace points

On 12/8/2015 12:25 PM, Steven Rostedt wrote:
> On Tue,  8 Dec 2015 11:39:50 -0800
> Yang Shi <yang.shi@linaro.org> wrote:
>
>> For slow version, just add trace point for raw __get_user_pages since all
>> slow variants call it to do the real work finally.
>>
>> Signed-off-by: Yang Shi <yang.shi@linaro.org>
>> ---
>>   mm/gup.c | 8 ++++++++
>>   1 file changed, 8 insertions(+)
>>
>> diff --git a/mm/gup.c b/mm/gup.c
>> index deafa2c..44f05c9 100644
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -18,6 +18,9 @@
>>
>>   #include "internal.h"
>>
>> +#define CREATE_TRACE_POINTS
>> +#include <trace/events/gup.h>
>> +
>>   static struct page *no_page_table(struct vm_area_struct *vma,
>>   		unsigned int flags)
>>   {
>> @@ -462,6 +465,8 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
>>   	if (!nr_pages)
>>   		return 0;
>>
>> +	trace_gup_get_user_pages(start, nr_pages);
>> +
>>   	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
>>
>>   	/*
>> @@ -599,6 +604,7 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
>>   	if (!(vm_flags & vma->vm_flags))
>>   		return -EFAULT;
>>
>> +	trace_gup_fixup_user_fault(address);
>>   	ret = handle_mm_fault(mm, vma, address, fault_flags);
>>   	if (ret & VM_FAULT_ERROR) {
>>   		if (ret & VM_FAULT_OOM)
>> @@ -1340,6 +1346,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
>>   					start, len)))
>>   		return 0;
>>
>> +	trace_gup_get_user_pages_fast(start, (unsigned long) nr_pages);
>
> typecast shouldn't be needed. But I'm wondering, it would save space in
> the ring buffer if we used unsigend int instead of long. Will nr_pages
> ever be bigger than 4 billion?

The "unsigned long" comes from get_user_pages() definition, I'm not 
quite sure why "unsigned long" is used. The fast version uses int (I 
guess unsigned int sounds better since it will not go negative).

"unsigned int" could cover 0xffffffff pages (almost 16TB), it sounds 
good enough in the most use case to me. In my test, just 1 page is 
passed to nr_pages in the most cases.

Thanks,
Yang

>
> -- Steve
>
>> +
>>   	/*
>>   	 * Disable interrupts.  We use the nested form as we can already have
>>   	 * interrupts disabled by get_futex_key.
>

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#1286813 — [PATCH v3 3/7] x86: mm/gup: add gup trace points

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
 arch/x86/mm/gup.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index ae9a37b..081f69d 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -12,6 +12,9 @@
 
 #include <asm/pgtable.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/gup.h>>
+
 static inline pte_t gup_get_pte(pte_t *ptep)
 {
 #ifndef CONFIG_X86_PAE
@@ -270,6 +273,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 					(void __user *)start, len)))
 		return 0;
 
+	trace_gup_get_user_pages_fast(start, (unsigned long) nr_pages);
+
 	/*
 	 * XXX: batch / limit 'nr', to avoid large irq off latency
 	 * needs some instrumenting to determine the common sizes used by
@@ -373,6 +378,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
 	} while (pgdp++, addr = next, addr != end);
 	local_irq_enable();
 
+	trace_gup_get_user_pages_fast(start, (unsigned long) nr_pages);
+
 	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
 	return nr;
 
-- 
2.0.2

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#1286814 — [PATCH v3 5/7] s390: mm/gup: add gup trace points

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
 arch/s390/mm/gup.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 12bbf0e..bbd82bf 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -12,6 +12,9 @@
 #include <linux/rwsem.h>
 #include <asm/pgtable.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/gup.h>
+
 /*
  * The performance critical leaf functions are made noinline otherwise gcc
  * inlines everything into a single function which results in too much
@@ -188,6 +191,9 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 	end = start + len;
 	if ((end <= start) || (end > TASK_SIZE))
 		return 0;
+
+	trace_gup_get_user_pages_fast(start, (unsigned long) nr_pages);
+
 	/*
 	 * local_irq_save() doesn't prevent pagetable teardown, but does
 	 * prevent the pagetables from being freed on s390.
-- 
2.0.2

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#1286815 — [PATCH v3 4/7] mips: mm/gup: add gup trace points

Cc: linux-mips@linux-mips.org
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
 arch/mips/mm/gup.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/mips/mm/gup.c b/arch/mips/mm/gup.c
index 349995d..2107499 100644
--- a/arch/mips/mm/gup.c
+++ b/arch/mips/mm/gup.c
@@ -15,6 +15,9 @@
 #include <asm/cpu-features.h>
 #include <asm/pgtable.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/gup.h>
+
 static inline pte_t gup_get_pte(pte_t *ptep)
 {
 #if defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
@@ -211,6 +214,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 					(void __user *)start, len)))
 		return 0;
 
+	trace_gup_get_user_pages_fast(start, (unsigned long) nr_pages);
+
 	/*
 	 * XXX: batch / limit 'nr', to avoid large irq off latency
 	 * needs some instrumenting to determine the common sizes used by
@@ -291,6 +296,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
 	} while (pgdp++, addr = next, addr != end);
 	local_irq_enable();
 
+	trace_gup_get_user_pages_fast(start, (unsigned long) nr_pages);
+
 	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
 	return nr;
 slow:
-- 
2.0.2

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