From: David Vernet <void@manifault.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, vschneid@redhat.com, gautham.shenoy@amd.com,
kprateek.nayak@amd.com, aaron.lu@intel.com, clm@meta.com,
tj@kernel.org, roman.gushchin@linux.dev, kernel-team@meta.com
Subject: [PATCH v2 3/7] sched: Check cpu_active() earlier in newidle_balance()
Date: Mon, 10 Jul 2023 15:03:38 -0500 [thread overview]
Message-ID: <20230710200342.358255-4-void@manifault.com> (raw)
In-Reply-To: <20230710200342.358255-1-void@manifault.com>
In newidle_balance(), we check if the current CPU is inactive, and then
decline to pull any remote tasks to the core if so. Before this check,
however, we're currently updating rq->idle_stamp. If a core is offline,
setting its idle stamp is not useful. The core won't be chosen by any
task in select_task_rq_fair(), and setting the rq->idle_stamp is
misleading anyways given that the core being inactive should imply that
it should have a very cold cache.
Let's set rq->idle_stamp in newidle_balance() only if the cpu is active.
Signed-off-by: David Vernet <void@manifault.com>
---
kernel/sched/fair.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a80a73909dc2..6e882b7bf5b4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11837,18 +11837,18 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
if (this_rq->ttwu_pending)
return 0;
- /*
- * We must set idle_stamp _before_ calling idle_balance(), such that we
- * measure the duration of idle_balance() as idle time.
- */
- this_rq->idle_stamp = rq_clock(this_rq);
-
/*
* Do not pull tasks towards !active CPUs...
*/
if (!cpu_active(this_cpu))
return 0;
+ /*
+ * We must set idle_stamp _before_ calling idle_balance(), such that we
+ * measure the duration of idle_balance() as idle time.
+ */
+ this_rq->idle_stamp = rq_clock(this_rq);
+
/*
* This is OK, because current is on_cpu, which avoids it being picked
* for load-balance and preemption/IRQs are still disabled avoiding
--
2.40.1
next prev parent reply other threads:[~2023-07-10 20:04 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-10 20:03 [PATCH v2 0/7] sched: Implement shared runqueue in CFS David Vernet
2023-07-10 20:03 ` [PATCH v2 1/7] sched: Expose move_queued_task() from core.c David Vernet
2023-07-10 20:03 ` [PATCH v2 2/7] sched: Move is_cpu_allowed() into sched.h David Vernet
2023-07-10 20:03 ` David Vernet [this message]
2023-07-10 20:03 ` [PATCH v2 4/7] sched/fair: Add SHARED_RUNQ sched feature and skeleton calls David Vernet
2023-07-11 9:45 ` Peter Zijlstra
2023-07-11 16:19 ` David Vernet
2023-07-12 8:39 ` Abel Wu
2023-07-12 21:34 ` David Vernet
2023-07-10 20:03 ` [PATCH v2 5/7] sched: Implement shared runqueue in CFS David Vernet
2023-07-11 10:18 ` Peter Zijlstra
2023-07-11 16:26 ` David Vernet
2023-07-12 6:00 ` Gautham R. Shenoy
2023-07-12 19:13 ` David Vernet
2023-07-12 10:47 ` Abel Wu
2023-07-12 22:16 ` David Vernet
2023-07-13 3:43 ` Abel Wu
2023-07-13 4:05 ` David Vernet
2023-07-13 7:58 ` Aaron Lu
2023-07-13 8:29 ` Peter Zijlstra
2023-07-10 20:03 ` [PATCH v2 6/7] sched: Shard per-LLC shared runqueues David Vernet
2023-07-11 10:49 ` Peter Zijlstra
2023-07-11 19:57 ` David Vernet
2023-07-12 10:06 ` Gautham R. Shenoy
2023-07-12 12:22 ` Peter Zijlstra
2023-07-10 20:03 ` [PATCH v2 7/7] sched: Move shared_runq to __{enqueue,dequeue}_entity() David Vernet
2023-07-11 10:51 ` Peter Zijlstra
2023-07-11 16:30 ` David Vernet
2023-07-11 11:42 ` [PATCH v2 0/7] sched: Implement shared runqueue in CFS Peter Zijlstra
2023-07-11 21:33 ` David Vernet
2023-07-21 9:12 ` Gautham R. Shenoy
2023-07-25 20:22 ` David Vernet
2023-08-02 6:32 ` Gautham R. Shenoy
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