linux-kernel - Re: [RFC PATCH 2/5] sched: Add NOHZ_STATS

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20180118103234.GC28799@e105550-lin.cambridge.arm.com>
Date:   Thu, 18 Jan 2018 10:32:34 +0000
From:   Morten Rasmussen <morten.rasmussen@...s.arm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Brendan Jackman <brendan.jackman@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>
Subject: Re: [RFC PATCH 2/5] sched: Add NOHZ_STATS_KICK

On Mon, Jan 15, 2018 at 10:43:18AM +0100, Peter Zijlstra wrote:
> On Tue, Jan 02, 2018 at 03:44:57PM +0000, Morten Rasmussen wrote:
> 
> > Vincent already proposed, why can't we just modify Brendan's
> > CPU_NEWLY_IDLE proposal to do a stats update from idle_balance() every
> > 32ms regardless of whether we need to load-balance?
> 
> I think that code is there, no?
> 
> Subject: sched: Update blocked load from NEWIDLE

The mechanics are there, but I think the problem is that the
idle_balance() bails out before we get to it in some cases. If we only
have a few small periodic tasks running rd->overload won't be set and
idle_balance() returns before doing anything.

We would need some sort of check to see if a PELT update is due and make
sure it happens, even if idle_balance() has nothing to do.