linux-kernel - Re: [lkp] [futex] 65d8fc777f: +25.6% will-it-scale.per_process

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Date:	Mon, 29 Feb 2016 09:37:47 -0800
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	kernel test robot <ying.huang@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>, lkp@...org,
	LKML <linux-kernel@...r.kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Darren Hart <dvhart@...ux.intel.com>, Chris Mason <clm@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Davidlohr Bueso <dbueso@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [lkp] [futex] 65d8fc777f: +25.6% will-it-scale.per_process_ops

On Mon, 29 Feb 2016, Ingo Molnar wrote:

>
>* kernel test robot <ying.huang@...ux.intel.com> wrote:
>
>> FYI, we noticed the below changes on
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>> commit 65d8fc777f6dcfee12785c057a6b57f679641c90 ("futex: Remove requirement for
>> lock_page() in get_futex_key()")
>
>I have asked for this before, but let me try again: could you _PLEASE_ make these
>emails more readable?
>
>For example what are the 'below changes'? Changes in the profile output? Profiles
>always change from run to run, so that alone is not informative.
>
>Also, there are a lot of changes - which ones prompted the email to be generated?
>
>All in one, this email is hard to parse, because it just dumps a lot of
>information with very little explanatory structure for someone not versed in their
>format. Please try to create an easy to parse 'story' that leads the reader
>towards what you want these emails to tell - not just a raw dump of seemingly
>unconnected pieces of data ...
>â
>Thanks,
>
>	Ingo
>
>>
>>
>> =========================================================================================
>> compiler/cpufreq_governor/kconfig/rootfs/tbox_group/test/testcase:
>>   gcc-4.9/performance/x86_64-rhel/debian-x86_64-2015-02-07.cgz/lkp-sbx04/futex1/will-it-scale

If I'm reading this correctly, it is similar to what I measured wrt ~lockleless get_futex_key()
stuff using the perf runs, with similar performance improvement numbers (per process/thread ops).
The futex1 test will just pound on FUTEX_WAKE without anyone actually blocked on a futex, so it
mainly measures the key/hashing part of the operation.

Thanks,
Davidlohr