On 02/26/2016 01:58 AM, [email protected] wrote:
> From: Joonsoo Kim <[email protected]>
>
> CMA allocation should be guaranteed to succeed by definition, but,
> unfortunately, it would be failed sometimes. It is hard to track down
> the problem, because it is related to page reference manipulation and
> we don't have any facility to analyze it.
>
> This patch adds tracepoints to track down page reference manipulation.
> With it, we can find exact reason of failure and can fix the problem.
> Following is an example of tracepoint output. (note: this example is
> stale version that printing flags as the number. Recent version will
> print it as human readable string.)
>
> Enabling this feature bloat kernel text 30 KB in my configuration.
>
> text data bss dec hex filename
> 12127327 2243616 1507328 15878271 f2487f vmlinux_disabled
> 12157208 2258880 1507328 15923416 f2f8d8 vmlinux_enabled
>
That's not bad, and it's even configurable. Thanks for taking the extra
care about overhead since v1.
> Note that, due to header file dependency problem between mm.h and
> tracepoint.h, this feature has to open code the static key functions
> for tracepoints. Proposed by Steven Rostedt in following link.
>
> https://lkml.org/lkml/2015/12/9/699
>
> v3:
> o Add commit description and code comment why this patch open code
> the static key functions for tracepoints.
> o Notify that example is stale version.
> o Add "depends on TRACEPOINTS".
>
> v2:
> o Use static key of each tracepoints to avoid function call overhead
> when tracepoints are disabled.
> o Print human-readable page flag thanks to newly introduced %pgp option.
> o Add more description to Kconfig.debug.
>
> Acked-by: Michal Nazarewicz <[email protected]>
> Signed-off-by: Joonsoo Kim <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
> +config DEBUG_PAGE_REF
> + bool "Enable tracepoint to track down page reference manipulation"
> + depends on DEBUG_KERNEL
> + depends on TRACEPOINTS
> + ---help---
> + This is the feature to add tracepoint for tracking down page reference
> + manipulation. This tracking is useful to diagnosis functional failure
> + due to migration failure caused by page reference mismatch. Be
OK.
> + careful to turn on this feature because it could bloat some kernel
> + text. In my configuration, it bloats 30 KB. Although kernel text will
> + be bloated, there would be no runtime performance overhead if
> + tracepoint isn't enabled thanks to jump label.
I would just write something like:
Enabling this feature adds about 30 KB to the kernel code, but runtime
performance overhead is virtually none until the tracepoints are
actually enabled.
2016-03-03 1:58 GMT+09:00 Vlastimil Babka <[email protected]>:
> On 02/26/2016 01:58 AM, [email protected] wrote:
>>
>> From: Joonsoo Kim <[email protected]>
>>
>> CMA allocation should be guaranteed to succeed by definition, but,
>> unfortunately, it would be failed sometimes. It is hard to track down
>> the problem, because it is related to page reference manipulation and
>> we don't have any facility to analyze it.
>>
>> This patch adds tracepoints to track down page reference manipulation.
>> With it, we can find exact reason of failure and can fix the problem.
>> Following is an example of tracepoint output. (note: this example is
>> stale version that printing flags as the number. Recent version will
>> print it as human readable string.)
>>
>> Enabling this feature bloat kernel text 30 KB in my configuration.
>>
>> text data bss dec hex filename
>> 12127327 2243616 1507328 15878271 f2487f vmlinux_disabled
>> 12157208 2258880 1507328 15923416 f2f8d8 vmlinux_enabled
>>
>
> That's not bad, and it's even configurable. Thanks for taking the extra care
> about overhead since v1.
>
>> Note that, due to header file dependency problem between mm.h and
>> tracepoint.h, this feature has to open code the static key functions
>> for tracepoints. Proposed by Steven Rostedt in following link.
>>
>> https://lkml.org/lkml/2015/12/9/699
>>
>> v3:
>> o Add commit description and code comment why this patch open code
>> the static key functions for tracepoints.
>> o Notify that example is stale version.
>> o Add "depends on TRACEPOINTS".
>>
>> v2:
>> o Use static key of each tracepoints to avoid function call overhead
>> when tracepoints are disabled.
>> o Print human-readable page flag thanks to newly introduced %pgp option.
>> o Add more description to Kconfig.debug.
>>
>> Acked-by: Michal Nazarewicz <[email protected]>
>> Signed-off-by: Joonsoo Kim <[email protected]>
>
>
> Acked-by: Vlastimil Babka <[email protected]>
>
>> +config DEBUG_PAGE_REF
>> + bool "Enable tracepoint to track down page reference manipulation"
>> + depends on DEBUG_KERNEL
>> + depends on TRACEPOINTS
>> + ---help---
>> + This is the feature to add tracepoint for tracking down page
>> reference
>> + manipulation. This tracking is useful to diagnosis functional
>> failure
>> + due to migration failure caused by page reference mismatch. Be
>
>
> OK.
>
>> + careful to turn on this feature because it could bloat some
>> kernel
>> + text. In my configuration, it bloats 30 KB. Although kernel text
>> will
>> + be bloated, there would be no runtime performance overhead if
>> + tracepoint isn't enabled thanks to jump label.
>
>
> I would just write something like:
>
> Enabling this feature adds about 30 KB to the kernel code, but runtime
> performance overhead is virtually none until the tracepoints are actually
> enabled.
Okay, better!
Andrew, do you want fixup patch from me or could you simply handle it?
Thanks.
On Thu, 3 Mar 2016 16:43:49 +0900 Joonsoo Kim <[email protected]> wrote:
> > Acked-by: Vlastimil Babka <[email protected]>
> >
> >> +config DEBUG_PAGE_REF
> >> + bool "Enable tracepoint to track down page reference manipulation"
> >> + depends on DEBUG_KERNEL
> >> + depends on TRACEPOINTS
> >> + ---help---
> >> + This is the feature to add tracepoint for tracking down page
> >> reference
> >> + manipulation. This tracking is useful to diagnosis functional
> >> failure
> >> + due to migration failure caused by page reference mismatch. Be
> >
> >
> > OK.
> >
> >> + careful to turn on this feature because it could bloat some
> >> kernel
> >> + text. In my configuration, it bloats 30 KB. Although kernel text
> >> will
> >> + be bloated, there would be no runtime performance overhead if
> >> + tracepoint isn't enabled thanks to jump label.
> >
> >
> > I would just write something like:
> >
> > Enabling this feature adds about 30 KB to the kernel code, but runtime
> > performance overhead is virtually none until the tracepoints are actually
> > enabled.
>
> Okay, better!
> Andrew, do you want fixup patch from me or could you simply handle it?
>
This?
--- a/mm/Kconfig.debug~mm-page_ref-add-tracepoint-to-track-down-page-reference-manipulation-fix-3-fix
+++ a/mm/Kconfig.debug
@@ -82,10 +82,9 @@ config DEBUG_PAGE_REF
depends on DEBUG_KERNEL
depends on TRACEPOINTS
---help---
- This is the feature to add tracepoint for tracking down page reference
- manipulation. This tracking is useful to diagnosis functional failure
- due to migration failure caused by page reference mismatch. Be
- careful to turn on this feature because it could bloat some kernel
- text. In my configuration, it bloats 30 KB. Although kernel text will
- be bloated, there would be no runtime performance overhead if
- tracepoint isn't enabled thanks to jump label.
+ This is a feature to add tracepoint for tracking down page reference
+ manipulation. This tracking is useful to diagnose functional failure
+ due to migration failures caused by page reference mismatches. Be
+ careful when enabling this feature because it adds about 30 KB to the
+ kernel code. However the runtime performance overhead is virtually
+ nil until the tracepoints are actually enabled.
_
On Fri, Mar 04, 2016 at 12:04:39PM -0800, Andrew Morton wrote:
> On Thu, 3 Mar 2016 16:43:49 +0900 Joonsoo Kim <[email protected]> wrote:
>
> > > Acked-by: Vlastimil Babka <[email protected]>
> > >
> > >> +config DEBUG_PAGE_REF
> > >> + bool "Enable tracepoint to track down page reference manipulation"
> > >> + depends on DEBUG_KERNEL
> > >> + depends on TRACEPOINTS
> > >> + ---help---
> > >> + This is the feature to add tracepoint for tracking down page
> > >> reference
> > >> + manipulation. This tracking is useful to diagnosis functional
> > >> failure
> > >> + due to migration failure caused by page reference mismatch. Be
> > >
> > >
> > > OK.
> > >
> > >> + careful to turn on this feature because it could bloat some
> > >> kernel
> > >> + text. In my configuration, it bloats 30 KB. Although kernel text
> > >> will
> > >> + be bloated, there would be no runtime performance overhead if
> > >> + tracepoint isn't enabled thanks to jump label.
> > >
> > >
> > > I would just write something like:
> > >
> > > Enabling this feature adds about 30 KB to the kernel code, but runtime
> > > performance overhead is virtually none until the tracepoints are actually
> > > enabled.
> >
> > Okay, better!
> > Andrew, do you want fixup patch from me or could you simply handle it?
> >
>
> This?
Yep!
Thanks!
>
> --- a/mm/Kconfig.debug~mm-page_ref-add-tracepoint-to-track-down-page-reference-manipulation-fix-3-fix
> +++ a/mm/Kconfig.debug
> @@ -82,10 +82,9 @@ config DEBUG_PAGE_REF
> depends on DEBUG_KERNEL
> depends on TRACEPOINTS
> ---help---
> - This is the feature to add tracepoint for tracking down page reference
> - manipulation. This tracking is useful to diagnosis functional failure
> - due to migration failure caused by page reference mismatch. Be
> - careful to turn on this feature because it could bloat some kernel
> - text. In my configuration, it bloats 30 KB. Although kernel text will
> - be bloated, there would be no runtime performance overhead if
> - tracepoint isn't enabled thanks to jump label.
> + This is a feature to add tracepoint for tracking down page reference
> + manipulation. This tracking is useful to diagnose functional failure
> + due to migration failures caused by page reference mismatches. Be
> + careful when enabling this feature because it adds about 30 KB to the
> + kernel code. However the runtime performance overhead is virtually
> + nil until the tracepoints are actually enabled.
> _
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to [email protected]. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"[email protected]"> [email protected] </a>