linux-kernel - Re: [Question]: try to fix contention between expire_timers and try_to_del_timer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170815184039.GE10801@arm.com>
Date:   Tue, 15 Aug 2017 19:40:40 +0100
From:   Will Deacon <will.deacon@....com>
To:     Vikram Mulukutla <markivx@...eaurora.org>
Cc:     qiaozhou <qiaozhou@...micro.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>, sboyd@...eaurora.org,
        LKML <linux-kernel@...r.kernel.org>,
        Wang Wilbur <wilburwang@...micro.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel-owner@...r.kernel.org, sudeep.holla@....com
Subject: Re: [Question]: try to fix contention between expire_timers and
 try_to_del_timer_sync

Hi Vikram,

On Thu, Aug 03, 2017 at 04:25:12PM -0700, Vikram Mulukutla wrote:
> On 2017-07-31 06:13, Will Deacon wrote:
> >On Fri, Jul 28, 2017 at 12:09:38PM -0700, Vikram Mulukutla wrote:
> >>On 2017-07-28 02:28, Will Deacon wrote:
> >>>On Thu, Jul 27, 2017 at 06:10:34PM -0700, Vikram Mulukutla wrote:
> 
> >>>
> >>This does seem to help. Here's some data after 5 runs with and without
> >>the
> >>patch.
> >
> >Blimey, that does seem to make a difference. Shame it's so ugly! Would you
> >be able to experiment with other values for CPU_RELAX_WFE_THRESHOLD? I had
> >it set to 10000 in the diff I posted, but that might be higher than
> >optimal.
> >It would be interested to see if it correlates with num_possible_cpus()
> >for the highly contended case.
> >
> >Will
> 
> Sorry for the late response - I should hopefully have some more data with
> different thresholds before the week is finished or on Monday.

Did you get anywhere with the threshold heuristic?

Will