linux-kernel - Re: [RFC PATCH] sched: fix the nonsense shares when load of cfs

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: <20200304095209.GK2596@hirez.programming.kicks-ass.net>
Date:   Wed, 4 Mar 2020 10:52:09 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     王贇 <yun.wang@...ux.alibaba.com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        "open list:SCHEDULER" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] sched: fix the nonsense shares when load of cfs_rq
 is too, small

On Wed, Mar 04, 2020 at 09:47:34AM +0100, Vincent Guittot wrote:
> you will add +1 of nice prio for each device
> 
> should we use instead
> # define scale_load_down(w) ((w >> SCHED_FIXEDPOINT_SHIFT) ? (w >>
> SCHED_FIXEDPOINT_SHIFT) : MIN_SHARES)

That's '((w >> SHIFT) ?: MIN_SHARES)', but even that is not quite right.

I think we want something like:

#define scale_load_down(w) \
({ unsigned long ___w = (w); \
   if (___w) \
     ____w = max(MIN_SHARES, ___w >> SHIFT); \
   ___w; })

That is, we very much want to retain 0 I'm thinking.