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Mon, 04 Aug 2025 04:48:31 -0700 (PDT) Date: Mon, 4 Aug 2025 19:48:22 +0800 From: Aaron Lu To: K Prateek Nayak Cc: Valentin Schneider , Ben Segall , Peter Zijlstra , Chengming Zhou , Josh Don , Ingo Molnar , Vincent Guittot , Xi Wang , linux-kernel@vger.kernel.org, Juri Lelli , Dietmar Eggemann , Steven Rostedt , Mel Gorman , Chuyi Zhou , Jan Kiszka , Florian Bezdeka , Songtang Liu Subject: Re: [PATCH v3 0/5] Defer throttle when task exits to user Message-ID: <20250804114822.GB496@bytedance> References: <20250715071658.267-1-ziqianlu@bytedance.com> <5c79fc39-2a68-4b6b-ba4b-73f6a0f4a30d@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5c79fc39-2a68-4b6b-ba4b-73f6a0f4a30d@amd.com> On Mon, Aug 04, 2025 at 02:21:30PM +0530, K Prateek Nayak wrote: > Hello Aaron, > > On 7/15/2025 12:46 PM, Aaron Lu wrote: > > v3: > > - Keep throttled cfs_rq's PELT clock running as long as it still has > > entity queued, suggested by Benjamin Segall. I've folded this change > > into patch3; > > - Rebased on top of tip/sched/core, commit 2885daf47081 > > ("lib/smp_processor_id: Make migration check unconditional of SMP"). > > > > Hi Prateek, > > I've kept your tested-by tag(Thanks!) for v2 since I believe this pelt > > clock change should not affect things much, but let me know if you don't > > think that is appropriate. > > I've officially tested this series so it should be fine :) Good to hear this :) > > In addition to Jan's test, I also did some sanity test looking at PELT > and everything looks good for the simplest case - once busy loop inside > a cgroup that gets throttled. The per-task throttling behavior is > identical to the current behavior for this simplest case. > > If I find time, I'll look into nested hierarchies with wakeups to see > if I can spot anything odd there. I don't really have a good control > setup to compare against here but so far I haven't found anything odd > and it works as intended. > Thanks for all these tests. Best regards, Aaron > > > > Tests I've done: > > - Jan's rt deadlock reproducer[1]. Without this series, I saw rcu-stalls > > within 2 minutes and with this series, I do not see rcu-stalls after > > 10 minutes. > > - A stress test that creates a lot of pressure on fork/exit path and > > cgroup_threadgroup_rwsem. Without this series, the test will cause > > task hung in about 5 minutes and with this series, no problem found > > after several hours. Songtang wrote this test script and I've used it > > to verify the patches, thanks Songtang. > > I just noticed this script. I'll give this a spin too when I test > nested hierarchies. > > -- > Thanks and Regards, > Prateek