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Fri, 25 Sep 2026 16:30:03 +0000 (GMT) Received: from [9.124.212.213] (unknown [9.124.212.213]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 25 Sep 2026 16:30:03 +0000 (GMT) Message-ID: Date: Fri, 25 Sep 2026 22:00:02 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 09/13] sched/debug: Add migration stats due to non preferred CPUs To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, yury.norov@gmail.com, kprateek.nayak@amd.com, iii@linux.ibm.com, corbet@lwn.net, meted@linux.ibm.com, ynorov@nvidia.com, tglx@kernel.org, gregkh@linuxfoundation.org, pbonzini@redhat.com, seanjc@google.com, vschneid@redhat.com, huschle@linux.ibm.com, rostedt@goodmis.org, dietmar.eggemann@arm.com, maddy@linux.ibm.com, srikar@linux.ibm.com, hdanton@sina.com, chleroy@kernel.org, vineeth@bitbyteword.org, frederic@kernel.org, arighi@nvidia.com, pauld@redhat.com, christian.loehle@arm.com, tj@kernel.org, tommaso.cucinotta@gmail.com, maz@kernel.org, rafael@kernel.org, rdunlap@infradead.org, kernellwp@gmail.com, linux-doc@vger.kernel.org, jgross@suse.com, virtualization@lists.linux.dev, sunlightlinux@gmail.com References: <20260909135617.871006-1-sshegde@linux.ibm.com> <20260909135617.871006-10-sshegde@linux.ibm.com> <20260925154540.GO2009045@noisy.programming.kicks-ass.net> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <20260925154540.GO2009045@noisy.programming.kicks-ass.net> Content-Type: text/plain; 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On 9/25/26 9:15 PM, Peter Zijlstra wrote: > On Wed, Sep 09, 2026 at 07:26:13PM +0530, Shrikanth Hegde wrote: >> Add a new stat, >> - nr_migrations_cpu_non_preferred: number of migrations happened since >> a CPU was marked as non preferred due to high steal time. >> >> Signed-off-by: Shrikanth Hegde >> --- >> include/linux/sched.h | 1 + >> kernel/sched/core.c | 9 +++++++-- >> kernel/sched/debug.c | 1 + >> 3 files changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/sched.h b/include/linux/sched.h >> index d7cc77181ef9..48639b0c75d0 100644 >> --- a/include/linux/sched.h >> +++ b/include/linux/sched.h >> @@ -554,6 +554,7 @@ struct sched_statistics { >> u64 nr_failed_migrations_running; >> u64 nr_failed_migrations_hot; >> u64 nr_forced_migrations; >> + u64 nr_migrations_cpu_non_preferred; >> >> u64 nr_wakeups; >> u64 nr_wakeups_sync; >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index 458b8c6fd9af..fb8404bd47e2 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -11239,8 +11239,13 @@ static int sched_non_preferred_cpu_push_stop(void *arg) >> context_unsafe_alias(rq); >> >> if (task_rq(p) == rq && task_on_rq_queued(p) && >> - !is_migration_disabled(p)) >> - rq = __migrate_task(rq, &rf, p, cpu); >> + !is_migration_disabled(p)) { >> + struct rq *dest_rq = __migrate_task(rq, &rf, p, cpu); >> + >> + if (rq != dest_rq) >> + schedstat_inc(p->stats.nr_migrations_cpu_non_preferred); >> + rq = dest_rq; >> + } >> >> rq_unlock(rq, &rf); >> raw_spin_unlock_irq(&p->pi_lock); >> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c >> index fda10b3fa249..e6a3b516c703 100644 >> --- a/kernel/sched/debug.c >> +++ b/kernel/sched/debug.c >> @@ -1440,6 +1440,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns, >> P_SCHEDSTAT(nr_failed_migrations_running); >> P_SCHEDSTAT(nr_failed_migrations_hot); >> P_SCHEDSTAT(nr_forced_migrations); >> + P_SCHEDSTAT(nr_migrations_cpu_non_preferred); >> P_SCHEDSTAT(nr_wakeups); >> P_SCHEDSTAT(nr_wakeups_sync); >> P_SCHEDSTAT(nr_wakeups_migrate); > > Should we not also bump the schedstat version? I forgot the rules, but > you do change the output. And did we ever merge that perf schedstat > thing, then that probably needs 'fixing' for the new format too. This doesn't change /proc/schedstat. Tt does rather change in /proc//sched which isn't defined by version number IIRC. Also i don't recollect that perf sched stat using anything from /proc//sched I skimmed through this. https://lore.kernel.org/all/20260119175833.340369-1-swapnil.sapkal@amd.com/ So I don't think we need to update the version.