linux-kernel - Re: [PATCH] perf/x86: Add cond_resched() when allocate/release DS buffers

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: <20251028190422.GE3419281@noisy.programming.kicks-ass.net>
Date: Tue, 28 Oct 2025 20:04:22 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>, Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH] perf/x86: Add cond_resched() when allocate/release DS
 buffers

On Tue, Oct 28, 2025 at 12:02:58PM -0700, Namhyung Kim wrote:
> Hi Peter,
> 
> On Tue, Oct 28, 2025 at 04:27:47PM +0100, Peter Zijlstra wrote:
> > On Tue, Oct 28, 2025 at 03:15:18PM +0100, Peter Zijlstra wrote:
> > > On Mon, Oct 27, 2025 at 02:27:24PM -0700, Namhyung Kim wrote:
> > > > On large systems, it's possible to trigger sched latency warning during
> > > > the DS buffer allocation or release.  Add cond_resched() to avoid it.
> > > 
> > > We're >.< close to deleting cond_resched(), it makes absolutely no sense
> > > adding more.
> > 
> > Specifically, IIRC the plan was to do something like the below after the
> > next LTS release, and then continue to remove VOLUNTARY in subsequent
> > releases, leaving NONE the only option for the legacy architectures that
> > do not support preemption.
> 
> Thanks for your review!
> 
> I haven't followed the work in this area so was not aware of the
> PREEMPT_LAZY.  Looks great!  I hope it'll work well on server platforms
> with many batch jobs and interactive tasks.
> 
> I will drop my patch then.

Well, we've been trying to get people to test things... But
realistically people will only test once you force them. So we'll see.