[RFC V4] Add gup trace points support

[RFC V4] Add gup trace points support

[Yang Shi]

v4:
* Adopted Steven's suggestion to use "unsigned int" for nr_pages to save
  space in ring buffer since it is unlikely to have more than 0xffffffff
  pages are touched by gup in one invoke
* Remove unnecessray type cast

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.


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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[PATCH v4 1/7] trace/events: Add gup trace events

[Yang Shi]

page-faults events record the invoke to handle_mm_fault, but the invoke
may come from do_page_fault or gup. In some use cases, the finer event count
mey be needed, so add trace events support for:

__get_user_pages
__get_user_pages_fast
fixup_user_fault

Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
 include/trace/events/gup.h | 63 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 include/trace/events/gup.h

diff --git a/include/trace/events/gup.h b/include/trace/events/gup.h
new file mode 100644
index 0000000..ac0e011
--- /dev/null
+++ b/include/trace/events/gup.h
@@ -0,0 +1,63 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM gup
+
+#if !defined(_TRACE_GUP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_GUP_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(gup_fixup_user_fault,
+
+	TP_PROTO(unsigned long address),
+
+	TP_ARGS(address),
+
+	TP_STRUCT__entry(
+		__field(	unsigned long,	address		)
+	),
+
+	TP_fast_assign(
+		__entry->address	= address;
+	),
+
+	TP_printk("address=%lx",  __entry->address)
+);
+
+DECLARE_EVENT_CLASS(gup,
+
+	TP_PROTO(unsigned long start, unsigned int nr_pages),
+
+	TP_ARGS(start, nr_pages),
+
+	TP_STRUCT__entry(
+		__field(	unsigned long,	start		)
+		__field(	unsigned int,	nr_pages	)
+	),
+
+	TP_fast_assign(
+		__entry->start		= start;
+		__entry->nr_pages	= nr_pages;
+	),
+
+	TP_printk("start=%lx nr_pages=%d", __entry->start, __entry->nr_pages)
+);
+
+DEFINE_EVENT(gup, gup_get_user_pages,
+
+	TP_PROTO(unsigned long start, unsigned int nr_pages),
+
+	TP_ARGS(start, nr_pages)
+);
+
+DEFINE_EVENT(gup, gup_get_user_pages_fast,
+
+	TP_PROTO(unsigned long start, unsigned int nr_pages),
+
+	TP_ARGS(start, nr_pages)
+);
+
+#endif /* _TRACE_GUP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.0.2

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[PATCH v4 2/7] mm/gup: add gup trace points

[Yang Shi]

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..00a3cff 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, 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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[PATCH v4 3/7] x86: mm/gup: add gup trace points

[Yang Shi]

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..a96bcb7 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, 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, nr_pages);
+
 	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
 	return nr;
 
-- 
2.0.2

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[PATCH v4 4/7] mips: mm/gup: add gup trace points

[Yang Shi]

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..e0d8838 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, 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, nr_pages);
+
 	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
 	return nr;
 slow:
-- 
2.0.2

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[PATCH v4 5/7] s390: mm/gup: add gup trace points

[Yang Shi]

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..0ff7e92 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, 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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[PATCH v4 6/7] sh: mm/gup: add gup trace points

[Yang Shi]

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

diff --git a/arch/sh/mm/gup.c b/arch/sh/mm/gup.c
index e7af6a6..fa72aac 100644
--- a/arch/sh/mm/gup.c
+++ b/arch/sh/mm/gup.c
@@ -14,6 +14,9 @@
 #include <linux/highmem.h>
 #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_X2TLB
@@ -178,6 +181,8 @@ 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, nr_pages);
+
 	/*
 	 * This doesn't prevent pagetable teardown, but does prevent
 	 * the pagetables and pages from being freed.
@@ -244,6 +249,8 @@ 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, nr_pages);
+
 	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
 	return nr;
 
-- 
2.0.2

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[PATCH v4 7/7] sparc64: mm/gup: add gup trace points

[Yang Shi]

Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
 arch/sparc/mm/gup.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
index 2e5c4fc..d9f573c 100644
--- a/arch/sparc/mm/gup.c
+++ b/arch/sparc/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
@@ -174,6 +177,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 	len = (unsigned long) nr_pages << PAGE_SHIFT;
 	end = start + len;
 
+	trace_gup_get_user_pages_fast(start, nr_pages);
+
 	local_irq_save(flags);
 	pgdp = pgd_offset(mm, addr);
 	do {
@@ -236,6 +241,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
 
 	local_irq_enable();
 
+	trace_gup_get_user_pages_fast(start, nr_pages);
+
 	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
 	return nr;
 
-- 
2.0.2

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Re: [PATCH v4 3/7] x86: mm/gup: add gup trace points

[Steven Rostedt]

On Wed,  9 Dec 2015 09:29:20 -0800
Yang Shi <yang.shi@linaro.org> wrote:

> 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..a96bcb7 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>>

First off, does the above even compile?

Second, you already created the tracepoints in mm/gup.c, why are you
creating them here again? CREATE_TRACE_POINTS must be defined only once
per events/.h file.

-- Steve

> +
>  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, 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, nr_pages);
> +
>  	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
>  	return nr;
>  

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Re: [PATCH v4 3/7] x86: mm/gup: add gup trace points

[Shi, Yang]

On 12/9/2015 1:07 PM, Steven Rostedt wrote:
> On Wed,  9 Dec 2015 09:29:20 -0800
> Yang Shi <yang.shi@linaro.org> wrote:
>
>> 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..a96bcb7 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>>
>
> First off, does the above even compile?
>
> Second, you already created the tracepoints in mm/gup.c, why are you
> creating them here again? CREATE_TRACE_POINTS must be defined only once
> per events/.h file.

Sorry for that. The typo was introduced by git amend without running 
test build. The multiple definition of trace points was not caught by my 
shaky test script.

Will fix them soon.

Thanks,
Yang

>
> -- Steve
>
>> +
>>   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, 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, nr_pages);
>> +
>>   	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
>>   	return nr;
>>
>

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