linux-kernel - Re: [PATCH v5 1/3] sched/fair: Introduce the burstable CFS controller

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: <xm26pmxe4ib6.fsf@google.com>
Date:   Tue, 25 May 2021 14:25:33 -0700
From:   Benjamin Segall <bsegall@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     changhuaixin <changhuaixin@...ux.alibaba.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        dtcccc@...ux.alibaba.com, Juri Lelli <juri.lelli@...hat.com>,
        khlebnikov@...dex-team.ru,
        open list <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...e.de>, Ingo Molnar <mingo@...hat.com>,
        Odin Ugedal <odin@...d.al>, Odin Ugedal <odin@...dal.com>,
        pauld@...head.com, Paul Turner <pjt@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Shanpei Chen <shanpeic@...ux.alibaba.com>,
        Tejun Heo <tj@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        xiyou.wangcong@...il.com
Subject: Re: [PATCH v5 1/3] sched/fair: Introduce the burstable CFS controller

Peter Zijlstra <peterz@...radead.org> writes:

> On Mon, May 24, 2021 at 08:42:03PM +0800, changhuaixin wrote:
>
>> >> static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
>> >> @@ -4651,6 +4666,9 @@ static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
>> >> 	if (cfs_b->quota == RUNTIME_INF)
>> >> 		amount = min_amount;
>> >> 	else {
>> >> +		if (!cfs_b->period_active)
>> >> +			__refill_cfs_bandwidth_runtime(cfs_b);
>> > 
>> > Why this call?
>> 
>> As the cfs bandwidth timer stops on idle with runtime unfilled, refill runtime when it restarts to make
>> use of the underrun when period timer stops. Another way to do this might be:
>> 
>>         throttled = !list_empty(&cfs_b->throttled_cfs_rq);
>>         cfs_b->nr_periods += overrun;
>> 
>> +       __refill_cfs_bandwidth_runtime(cfs_b);
>> +
>>         /*
>>          * idle depends on !throttled (for the case of a large deficit), and if
>>          * we're going inactive then everything else can be deferred
>>          */
>>         if (cfs_b->idle && !throttled)
>>                 goto out_deactivate;
>> 
>> -       __refill_cfs_bandwidth_runtime(cfs_b);
>> -
>>         if (!throttled) {
>> 
>
> Ben, do you have a preference?


I think I prefer the latter, possibly with a
/* Refill extra burst quota even if cfs_b->idle */