linux-kernel - Re: [PATCH v2 0/5] Defer throttle when task exits to user

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: <20250702085139.GA789@bytedance>
Date: Wed, 2 Jul 2025 16:51:39 +0800
From: Aaron Lu <ziqianlu@...edance.com>
To: K Prateek Nayak <kprateek.nayak@....com>
Cc: Valentin Schneider <vschneid@...hat.com>,
	Ben Segall <bsegall@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Chengming Zhou <chengming.zhou@...ux.dev>,
	Josh Don <joshdon@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Xi Wang <xii@...gle.com>, linux-kernel@...r.kernel.org,
	Juri Lelli <juri.lelli@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>, Mel Gorman <mgorman@...e.de>,
	Chuyi Zhou <zhouchuyi@...edance.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Florian Bezdeka <florian.bezdeka@...mens.com>
Subject: Re: [PATCH v2 0/5] Defer throttle when task exits to user

Hi Prateek,

On Wed, Jul 02, 2025 at 09:55:19AM +0530, K Prateek Nayak wrote:
> Hello Aaron,
> 
> On 6/18/2025 1:49 PM, Aaron Lu wrote:
> > v2:
> > - Re-org the patchset to use a single patch to implement throttle
> >    related changes, suggested by Chengming;
> > - Use check_cfs_rq_runtime()'s return value in pick_task_fair() to
> >    decide if throttle task work is needed instead of checking
> >    throttled_hierarchy(), suggested by Peter;
> > - Simplify throttle_count check in tg_throtthe_down() and
> >    tg_unthrottle_up(), suggested by Peter;
> > - Add enqueue_throttled_task() to speed up enqueuing a throttled task to
> >    a throttled cfs_rq, suggested by Peter;
> > - Address the missing of detach_task_cfs_rq() for throttled tasks that
> >    get migrated to a new rq, pointed out by Chengming;
> > - Remove cond_resched_tasks_rcu_qs() in throttle_cfs_rq_work() as
> >    cond_resched*() is going away, pointed out by Peter.
> > I hope I didn't miss any comments and suggestions for v1 and if I do,
> > please kindly let me know, thanks!
> > 
> > Base: tip/sched/core commit dabe1be4e84c("sched/smp: Use the SMP version
> > of double_rq_clock_clear_update()")
> 
> Sorry for the delay! I gave this a spin with my nested hierarchy stress
> test with sched-messaging as well as with Jan's reproducer from [1] and
> I didn't see anything unexpected.
> 
> A 2 vCPU VM running vanilla tip:sched/core (PREEMPT_RT) hangs within a
> few seconds when the two tasks from Jan's reproducer are pinned to the
> same CPU as the bandwidth timer.
> 
> I haven't seen any hangs / rcu-stalls with this series applied on top of
> tip:sched/core. Feel free to include:
> 
> Tested-by: K Prateek Nayak <kprateek.nayak@....com>
> 
> [1] https://lore.kernel.org/all/7483d3ae-5846-4067-b9f7-390a614ba408@siemens.com/
>

Thanks a lot Prateek, I really appreciate your time on testing this.

Best regards,
Aaron