[PATCH] Documentation: statistics about nested locks

[PATCH] Documentation: statistics about nested locks

[Juri Lelli]

Hi all,
just a little patch to the Documentation. I had some trouble 
understanding the trailing "/1" on some lock class names of lock_stat 
output, so I added something on this inside lockstat documentation.

Signed-off-by: Juri Lelli <juri.lelli@gmail.com>

---
  Documentation/lockstat.txt |   36 ++++++++++++++++++++++++++++++++++--
  1 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/Documentation/lockstat.txt b/Documentation/lockstat.txt
index 65f4c79..75eeb65 100644
--- a/Documentation/lockstat.txt
+++ b/Documentation/lockstat.txt
@@ -12,8 +12,9 @@ Because things like lock contention can severely 
impact performance.
  - HOW

  Lockdep already has hooks in the lock functions and maps lock instances to
-lock classes. We build on that. The graph below shows the relation between
-the lock functions and the various hooks therein.
+lock classes. We build on that (see Documentation/lockdep-design.txt).
+The graph below shows the relation between the lock functions and the 
various
+hooks therein.

          __acquire
              |
@@ -128,6 +129,37 @@ points are the points we're contending with.

  The integer part of the time values is in us.

+Dealing with nested locks, subclasses may appear:
+
+32...............................................................................................................................................................................................
+33
+34                               &rq->lock:         13128 
13128           0.43         190.53      103881.26          97454 
  3453404           0.00         401.11    13224683.11
+35                               ---------
+36                               &rq->lock            645 
[<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
+37                               &rq->lock            297 
[<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+38                               &rq->lock            360 
[<ffffffff8103c4c5>] select_task_rq_fair+0x1f0/0x74a
+39                               &rq->lock            428 
[<ffffffff81045f98>] scheduler_tick+0x46/0x1fb
+40                               ---------
+41                               &rq->lock             77 
[<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
+42                               &rq->lock            174 
[<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+43                               &rq->lock           4715 
[<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
+44                               &rq->lock            893 
[<ffffffff81340524>] schedule+0x157/0x7b8
+45
+46...............................................................................................................................................................................................
+47
+48                             &rq->lock/1:         11526 
11488           0.33         388.73      136294.31          21461 
    38404           0.00          37.93      109388.53
+49                             -----------
+50                             &rq->lock/1          11526 
[<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
+51                             -----------
+52                             &rq->lock/1           5645 
[<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
+53                             &rq->lock/1           1224 
[<ffffffff81340524>] schedule+0x157/0x7b8
+54                             &rq->lock/1           4336 
[<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
+55                             &rq->lock/1            181 
[<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+
+Line 48 shows statistics for the first subclass (/1) of &rq->lock 
class, since
+in this case, as line 50 suggests, double_rq_lock actually acquires a 
nested
+lock of two spinlocks.
+
  View the top contending locks:

  # grep : /proc/lock_stat | head
-- 
1.7.4.1

Re: [PATCH] Documentation: statistics about nested locks

[Peter Zijlstra]

On Mon, 2011-05-16 at 12:01 +0200, Juri Lelli wrote:
> +The graph below shows the relation between the lock functions and the 
> various
> +hooks therein. 

That smells like the patch has whitespace damage..

Re: [PATCH] Documentation: statistics about nested locks

[Ingo Molnar]

* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> On Mon, 2011-05-16 at 12:01 +0200, Juri Lelli wrote:
> > +The graph below shows the relation between the lock functions and the 
> > various
> > +hooks therein. 
> 
> That smells like the patch has whitespace damage..

Yeah, Documentation/email-clients.txt might help there.

Thanks,

	Ingo

Re: [PATCH] Documentation: statistics about nested locks

[Yong Zhang]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=UTF-8, Size: 4699 bytes --]

On Mon, May 16, 2011 at 6:01 PM, Juri Lelli <juri.lelli@gmail.com> wrote:
> Hi all,
> just a little patch to the Documentation. I had some trouble understanding
> the trailing "/1" on some lock class names of lock_stat output, so I added
> something on this inside lockstat documentation.
>
> Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
>
> ---
>  Documentation/lockstat.txt |   36 ++++++++++++++++++++++++++++++++++--
>  1 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/lockstat.txt b/Documentation/lockstat.txt
> index 65f4c79..75eeb65 100644
> --- a/Documentation/lockstat.txt
> +++ b/Documentation/lockstat.txt
> @@ -12,8 +12,9 @@ Because things like lock contention can severely impact
> performance.
>  - HOW
>
>  Lockdep already has hooks in the lock functions and maps lock instances to
> -lock classes. We build on that. The graph below shows the relation between
> -the lock functions and the various hooks therein.
> +lock classes. We build on that (see Documentation/lockdep-design.txt).
> +The graph below shows the relation between the lock functions and the
> various
> +hooks therein.
>
>         __acquire
>             |
> @@ -128,6 +129,37 @@ points are the points we're contending with.
>
>  The integer part of the time values is in us.
>
> +Dealing with nested locks, subclasses may appear:
> +
> +32...............................................................................................................................................................................................
> +33
> +34                               &rq->lock:         13128 13128
> 0.43         190.53      103881.26          97454  3453404           0.00
>       401.11    13224683.11
> +35                               ---------
> +36                               &rq->lock            645
> [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
> +37                               &rq->lock            297
> [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
> +38                               &rq->lock            360
> [<ffffffff8103c4c5>] select_task_rq_fair+0x1f0/0x74a
> +39                               &rq->lock            428
> [<ffffffff81045f98>] scheduler_tick+0x46/0x1fb
> +40                               ---------
> +41                               &rq->lock             77
> [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
> +42                               &rq->lock            174
> [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
> +43                               &rq->lock           4715
> [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
> +44                               &rq->lock            893
> [<ffffffff81340524>] schedule+0x157/0x7b8
> +45
> +46...............................................................................................................................................................................................
> +47
> +48                             &rq->lock/1:         11526 11488
> 0.33         388.73      136294.31          21461    38404           0.00
>        37.93      109388.53
> +49                             -----------
> +50                             &rq->lock/1          11526
> [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
> +51                             -----------
> +52                             &rq->lock/1           5645
> [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
> +53                             &rq->lock/1           1224
> [<ffffffff81340524>] schedule+0x157/0x7b8
> +54                             &rq->lock/1           4336
> [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
> +55                             &rq->lock/1            181
> [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
> +
> +Line 48 shows statistics for the first subclass (/1) of &rq->lock class,

Actually it's the second subclass because subclass starts from 0.

Thanks,
Yong

> since
> +in this case, as line 50 suggests, double_rq_lock actually acquires a
> nested
> +lock of two spinlocks.
> +
>  View the top contending locks:
>
>  # grep : /proc/lock_stat | head
> --
> 1.7.4.1
>



-- 
Only stand for myself
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Re: [PATCH] Documentation: statistics about nested locks

[Juri Lelli]

Sorry for my mistake with the email client and thanks for the hint!
May I resend a (I hope) corrected version of this small patch with the revision
made by Yong?

On 05/16/2011 12:35 PM, Ingo Molnar wrote:
> 
> * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> 
>> On Mon, 2011-05-16 at 12:01 +0200, Juri Lelli wrote:
>>> +The graph below shows the relation between the lock functions and the 
>>> various
>>> +hooks therein. 
>>
>> That smells like the patch has whitespace damage..
> 
> Yeah, Documentation/email-clients.txt might help there.
> 
> Thanks,
> 
> 	Ingo

Thanks,

	Juri

Re: [PATCH] Documentation: statistics about nested locks

[Yong Zhang]

On Tue, May 17, 2011 at 4:39 PM, Juri Lelli <juri.lelli@gmail.com> wrote:
> Sorry for my mistake with the email client and thanks for the hint!
> May I resend a (I hope) corrected version of this small patch with the revision
> made by Yong?

No problem on my side :)

Thanks,
Yong

>
> On 05/16/2011 12:35 PM, Ingo Molnar wrote:
>>
>> * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
>>
>>> On Mon, 2011-05-16 at 12:01 +0200, Juri Lelli wrote:
>>>> +The graph below shows the relation between the lock functions and the
>>>> various
>>>> +hooks therein.
>>>
>>> That smells like the patch has whitespace damage..
>>
>> Yeah, Documentation/email-clients.txt might help there.
>>
>> Thanks,
>>
>>       Ingo
>
> Thanks,
>
>        Juri
>



-- 
Only stand for myself