10:59 p.m.
Hi Andy,
FYI, we noticed the below changes on
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/vdso
commit cfda7bb9ecbf9d96264bb5bade33a842966d1062 ("x86, vdso: Move syscall and
sysenter setup into kernel/cpu/common.c")
test case: nhm4/will-it-scale/sched_yield
3d7ee969bffcc98 cfda7bb9ecbf9d96264bb5bad
--------------- -------------------------
5497021 ~ 0% +14.7% 6303424 ~ 0% TOTAL will-it-scale.per_thread_ops
0.54 ~ 0% +5.6% 0.57 ~ 0% TOTAL will-it-scale.scalability
6209483 ~ 0% +1.6% 6305917 ~ 0% TOTAL will-it-scale.per_process_ops
2455 ~ 5% +16.9% 2870 ~ 5% TOTAL cpuidle.C1-NHM.usage
8829 ~ 7% +15.2% 10169 ~10% TOTAL slabinfo.kmalloc-64.active_objs
24.13 ~12% +48.9% 35.93 ~14% TOTAL time.user_time
393 ~ 0% -3.0% 382 ~ 1% TOTAL time.system_time
Legend:
~XX% - stddev percent
[+-]XX% - change percent
Thanks,
Jet
3:46 p.m.
On Mon, May 19, 2014 at 10:59 PM, Jet Chen <jet.chen(a)intel.com> wrote:
Hi Andy,
FYI, we noticed the below changes on
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/vdso
commit cfda7bb9ecbf9d96264bb5bade33a842966d1062 ("x86, vdso: Move syscall
and sysenter setup into kernel/cpu/common.c")
This is really strange. That change shouldn't have any effect except
that some kernels might boot a cycle or two faster.
test case: nhm4/will-it-scale/sched_yield
3d7ee969bffcc98 cfda7bb9ecbf9d96264bb5bad
--------------- -------------------------
5497021 ~ 0% +14.7% 6303424 ~ 0% TOTAL
will-it-scale.per_thread_ops
0.54 ~ 0% +5.6% 0.57 ~ 0% TOTAL will-it-scale.scalability
6209483 ~ 0% +1.6% 6305917 ~ 0% TOTAL
will-it-scale.per_process_ops
2455 ~ 5% +16.9% 2870 ~ 5% TOTAL cpuidle.C1-NHM.usage
8829 ~ 7% +15.2% 10169 ~10% TOTAL
slabinfo.kmalloc-64.active_objs
24.13 ~12% +48.9% 35.93 ~14% TOTAL time.user_time
393 ~ 0% -3.0% 382 ~ 1% TOTAL time.system_time
Is this a speedup or a slowdown?
--Andy
6:54 p.m.
Hi Andy,
On Wed, May 21, 2014 at 03:46:58PM -0700, Andy Lutomirski wrote:
On Mon, May 19, 2014 at 10:59 PM, Jet Chen <jet.chen(a)intel.com>
wrote:
> Hi Andy,
>
> FYI, we noticed the below changes on
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/vdso
> commit cfda7bb9ecbf9d96264bb5bade33a842966d1062 ("x86, vdso: Move syscall
> and sysenter setup into kernel/cpu/common.c")
This is really strange. That change shouldn't have any effect except
that some kernels might boot a cycle or two faster.
>
> test case: nhm4/will-it-scale/sched_yield
>
> 3d7ee969bffcc98 cfda7bb9ecbf9d96264bb5bad
> --------------- -------------------------
> 5497021 ~ 0% +14.7% 6303424 ~ 0% TOTAL
> will-it-scale.per_thread_ops
> 0.54 ~ 0% +5.6% 0.57 ~ 0% TOTAL will-it-scale.scalability
> 6209483 ~ 0% +1.6% 6305917 ~ 0% TOTAL
> will-it-scale.per_process_ops
> 2455 ~ 5% +16.9% 2870 ~ 5% TOTAL cpuidle.C1-NHM.usage
> 8829 ~ 7% +15.2% 10169 ~10% TOTAL
> slabinfo.kmalloc-64.active_objs
> 24.13 ~12% +48.9% 35.93 ~14% TOTAL time.user_time
> 393 ~ 0% -3.0% 382 ~ 1% TOTAL time.system_time
>
Is this a speedup or a slowdown?
It's a speedup. The will-it-scale/sched_yield test case's throughput
increased by +14.7% (multi-thread case) and +1.6% (multi-process case).
However the CPU %user time increased more, by +48.9%.
Thanks,
Fengguang
10:03 p.m.
On 05/21/2014 06:54 PM, Fengguang Wu wrote:
>>
>> test case: nhm4/will-it-scale/sched_yield
>>
>> 3d7ee969bffcc98 cfda7bb9ecbf9d96264bb5bad
>> --------------- -------------------------
>> 5497021 ~ 0% +14.7% 6303424 ~ 0% TOTAL
>> will-it-scale.per_thread_ops
>> 0.54 ~ 0% +5.6% 0.57 ~ 0% TOTAL will-it-scale.scalability
>> 6209483 ~ 0% +1.6% 6305917 ~ 0% TOTAL
>> will-it-scale.per_process_ops
>> 2455 ~ 5% +16.9% 2870 ~ 5% TOTAL cpuidle.C1-NHM.usage
>> 8829 ~ 7% +15.2% 10169 ~10% TOTAL
>> slabinfo.kmalloc-64.active_objs
>> 24.13 ~12% +48.9% 35.93 ~14% TOTAL time.user_time
>> 393 ~ 0% -3.0% 382 ~ 1% TOTAL time.system_time
>>
>
> Is this a speedup or a slowdown?
It's a speedup. The will-it-scale/sched_yield test case's throughput
increased by +14.7% (multi-thread case) and +1.6% (multi-process case).
However the CPU %user time increased more, by +48.9%.
That would be consistent with spending less time in the kernel, no?
But I agree... that is completely bizarre. That checkin should have
absolutely zero effect on performance.
-hpa
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3 comments
4 participants
participants (4)
-
Andy Lutomirski -
Fengguang Wu -
H. Peter Anvin -
Jet Chen