linux-kernel - Re: [PATCH v2 0/2] Make reader optimistic spinning optional

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Date: Tue, 2 Apr 2024 16:46:06 -0700
From: John Stultz <jstultz@...gle.com>
To: Bongkyu Kim <bongkyu7.kim@...sung.com>
Cc: peterz@...radead.org, mingo@...hat.com, will@...nel.org, 
	longman@...hat.com, boqun.feng@...il.com, linux-kernel@...r.kernel.org, 
	gregkh@...uxfoundation.org
Subject: Re: [PATCH v2 0/2] Make reader optimistic spinning optional

On Thu, Aug 31, 2023 at 6:07 PM Bongkyu Kim <bongkyu7.kim@...sung.com> wrote:
>
> This is rework of the following discussed patch.
> https://lore.kernel.org/all/20230613043308.GA1027@KORCO045595.samsungds.net/
>
> Changes from the previous patch
> - Split to revert and modify patches
> - Change according to Waiman Long's review
>     More wording to documentation part
>     Change module_param to early_param
>     Code change by Waiman Long's suggestion
>
> In mobile environment, reader optimistic spinning is still useful
> because there're not many readers. In my test result at android device,
> it improves application startup time about 3.8%
> App startup time is most important factor for android user expriences.
> So, re-enable reader optimistic spinning by this commit. And,
> make it optional feature by cmdline.
>
> Test result:
> This is 15 application startup performance in our exynos soc.
> - Cortex A78*2 + Cortex A55*6
> - unit: ms (lower is better)
>
> Application             base  opt_rspin  Diff  Diff(%)
> --------------------  ------  ---------  ----  -------
> * Total(geomean)         343        330   -13    +3.8%
> --------------------  ------  ---------  ----  -------
> helloworld               110        108    -2    +1.8%
> Amazon_Seller            397        388    -9    +2.3%
> Whatsapp                 311        304    -7    +2.3%
> Simple_PDF_Reader        500        463   -37    +7.4%
> FaceApp                  330        317   -13    +3.9%
> Timestamp_Camera_Free    451        443    -8    +1.8%
> Kindle                   629        597   -32    +5.1%
> Coinbase                 243        233   -10    +4.1%
> Firefox                  425        399   -26    +6.1%
> Candy_Crush_Soda         552        538   -14    +2.5%
> Hill_Climb_Racing        245        230   -15    +6.1%
> Call_Recorder            437        426   -11    +2.5%
> Color_Fill_3D            190        180   -10    +5.3%
> eToro                    512        505    -7    +1.4%
> GroupMe                  281        266   -15    +5.3%
>

Hey Bongkyu,
  I wanted to reach out to see what the current status of this patch
set? I'm seeing other parties trying to work around the loss of the
optimistic spinning functionality since commit 617f3ef95177
("locking/rwsem: Remove reader optimistic spinning") as well, with
their own custom variants (providing some substantial gains), and
would really like to have a common solution.

thanks
-john