From: H. Peter Anvin <hpa@linux.intel.com>
To: lkp@lists.01.org
Subject: Re: [x86, vdso] cfda7bb9ecb: +14.7% will-it-scale.per_thread_ops
Date: Wed, 21 May 2014 22:03:39 -0700 [thread overview]
Message-ID: <537D852B.8070106@linux.intel.com> (raw)
In-Reply-To: <20140522015448.GA23196@localhost>
[-- Attachment #1: Type: text/plain, Size: 1231 bytes --]
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
WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@linux.intel.com>
To: Fengguang Wu <fengguang.wu@intel.com>,
Andy Lutomirski <luto@amacapital.net>
Cc: Jet Chen <jet.chen@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
lkp@01.org
Subject: Re: [x86, vdso] cfda7bb9ecb: +14.7% will-it-scale.per_thread_ops
Date: Wed, 21 May 2014 22:03:39 -0700 [thread overview]
Message-ID: <537D852B.8070106@linux.intel.com> (raw)
In-Reply-To: <20140522015448.GA23196@localhost>
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
next prev parent reply other threads:[~2014-05-22 5:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-20 5:59 [x86, vdso] cfda7bb9ecb: +14.7% will-it-scale.per_thread_ops Jet Chen
2014-05-20 5:59 ` Jet Chen
2014-05-21 22:46 ` Andy Lutomirski
2014-05-21 22:46 ` Andy Lutomirski
2014-05-22 1:54 ` Fengguang Wu
2014-05-22 1:54 ` Fengguang Wu
2014-05-22 5:03 ` H. Peter Anvin [this message]
2014-05-22 5:03 ` H. Peter Anvin
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