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Thu, 27 Aug 2026 19:20:20 -0700 (PDT) From: Zhan Xusheng To: tim.c.chen@linux.intel.com Cc: yu.c.chen@intel.com, peterz@infradead.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, linux-kernel@vger.kernel.org, zhanxusheng@xiaomi.com Subject: Re: [PATCH] sched/cache: Keep nr_pref_llc_running in the runnable domain Date: Fri, 28 Aug 2026 10:20:12 +0800 Message-ID: <20260828022012.936112-1-zhanxusheng1024@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <59e2b8265fc650266b93d8f523c366edfa912428.camel@linux.intel.com> References: <59e2b8265fc650266b93d8f523c366edfa912428.camel@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable From: Zhan Xusheng =0D The ordering the skip depends on is not visible in the diff, so for the=0D record: dequeue_hierarchy() at fair.c:8148 reaches account_llc_dequeue()=0D through dequeue_entity(), and clear_delayed() runs only afterwards at=0D 8164, so se->sched_delayed is still set when account_llc_dequeue() tests=0D it.=0D =0D The sequences balance:=0D =0D enqueue, dequeue +1, -1=0D enqueue, sleep, wake, dequeue +1, -1 set_delayed,=0D +1 clear_delayed, -1=0D enqueue, sleep, real dequeue +1, -1, skip, no re-add=0D load balance moves a delayed task source unchanged, destination +1=0D with sched_delayed already clear=0D =0D requeue_delayed_entity() does not reach account_entity_enqueue(), doing=0D only __enqueue_entity() and clear_delayed(), so the wake path cannot=0D double count. account_mm_sched() cannot see a delayed task either, since=0D task_running_on_cpu() at fair.c:12245 requires task_on_rq_queued() on the=0D current cpu and the caller is update_curr().=0D =0D sd->llc_counts is right to stay on queued semantics: both readers compare=0D it against another llc_counts value, at fair.c:11895 and 13228, so delayed= =0D tasks shift both sides alike.=0D =0D Reviewed-by: Zhan Xusheng =0D =0D Thanks,=0D Zhan Xusheng=0D