From: "Gautham R. Shenoy" <gautham.shenoy@amd.com>
To: David Vernet <void@manifault.com>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com,
peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, rostedt@goodmis.org,
dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, vschneid@redhat.com, joshdon@google.com,
roman.gushchin@linux.dev, tj@kernel.org, kernel-team@meta.com
Subject: Re: [RFC PATCH 3/3] sched: Implement shared wakequeue in CFS
Date: Mon, 19 Jun 2023 11:43:13 +0530 [thread overview]
Message-ID: <ZI/x+RkSqpct4bM3@BLR-5CG11610CF.amd.com> (raw)
In-Reply-To: <20230613052004.2836135-4-void@manifault.com>
Hello David,
On Tue, Jun 13, 2023 at 12:20:04AM -0500, David Vernet wrote:
[..snip..]
> +static void swqueue_enqueue(struct rq *rq, struct task_struct *p, int enq_flags)
> +{
> + unsigned long flags;
> + struct swqueue *swqueue;
> + bool task_migrated = enq_flags & ENQUEUE_MIGRATED;
> + bool task_wakeup = enq_flags & ENQUEUE_WAKEUP;
> +
> + /*
> + * Only enqueue the task in the shared wakequeue if:
> + *
> + * - SWQUEUE is enabled
> + * - The task is on the wakeup path
> + * - The task wasn't purposefully migrated to the current rq by
> + * select_task_rq()
> + * - The task isn't pinned to a specific CPU
> + */
> + if (!task_wakeup || task_migrated || p->nr_cpus_allowed == 1)
> + return;
In select_task_rq_fair(), having determined if the target of task
wakeup should be the task's previous CPU vs the waker's current CPU,
we spend quite a bit of time already to determine if there is an idle
core/CPU in the target's LLC. @rq would correspond to CPU chosen as a
result of that scan or if no idle CPU exists, @rq corresponds to the
target CPU determined by wake_affine_idle()/wake_affine_weight().
So if the CPU of @rq is idle here, can we not simply return here?
Or if the idea is to avoid the scan for an idle core/CPU in
select_task_rq_fair(), then
Perhaps I am missing something...
> +
> + swqueue = rq_swqueue(rq);
> + spin_lock_irqsave(&swqueue->lock, flags);
> + list_add_tail(&p->swqueue_node, &swqueue->list);
> + spin_unlock_irqrestore(&swqueue->lock, flags);
> +}
> +
--
Thanks and Regards
gautham.
next prev parent reply other threads:[~2023-06-19 6:13 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-13 5:20 [RFC PATCH 0/3] sched: Implement shared wakequeue in CFS David Vernet
2023-06-13 5:20 ` [RFC PATCH 1/3] sched: Make migrate_task_to() take any task David Vernet
2023-06-21 13:04 ` Peter Zijlstra
2023-06-22 2:07 ` David Vernet
2023-06-13 5:20 ` [RFC PATCH 2/3] sched/fair: Add SWQUEUE sched feature and skeleton calls David Vernet
2023-06-21 12:49 ` Peter Zijlstra
2023-06-22 14:53 ` David Vernet
2023-06-13 5:20 ` [RFC PATCH 3/3] sched: Implement shared wakequeue in CFS David Vernet
2023-06-13 8:32 ` Peter Zijlstra
2023-06-14 4:35 ` Aaron Lu
2023-06-14 9:27 ` Peter Zijlstra
2023-06-15 0:01 ` David Vernet
2023-06-15 4:49 ` Aaron Lu
2023-06-15 7:31 ` Aaron Lu
2023-06-15 23:26 ` David Vernet
2023-06-16 0:53 ` Aaron Lu
2023-06-20 17:36 ` David Vernet
2023-06-21 2:35 ` Aaron Lu
2023-06-21 2:43 ` David Vernet
2023-06-21 4:54 ` Aaron Lu
2023-06-21 5:43 ` David Vernet
2023-06-21 6:03 ` Aaron Lu
2023-06-22 15:57 ` Chris Mason
2023-06-13 8:41 ` Peter Zijlstra
2023-06-14 20:26 ` David Vernet
2023-06-16 8:08 ` Vincent Guittot
2023-06-20 19:54 ` David Vernet
2023-06-20 21:37 ` Roman Gushchin
2023-06-21 14:22 ` Peter Zijlstra
2023-06-19 6:13 ` Gautham R. Shenoy [this message]
2023-06-20 20:08 ` David Vernet
2023-06-21 8:17 ` Gautham R. Shenoy
2023-06-22 1:43 ` David Vernet
2023-06-22 9:11 ` Gautham R. Shenoy
2023-06-22 10:29 ` Peter Zijlstra
2023-06-23 9:50 ` Gautham R. Shenoy
2023-06-26 6:04 ` Gautham R. Shenoy
2023-06-27 3:17 ` David Vernet
2023-06-27 16:31 ` Chris Mason
2023-06-21 14:20 ` Peter Zijlstra
2023-06-21 20:34 ` David Vernet
2023-06-22 10:58 ` Peter Zijlstra
2023-06-22 14:43 ` David Vernet
2023-07-10 11:57 ` [RFC PATCH 0/3] " K Prateek Nayak
2023-07-11 4:43 ` David Vernet
2023-07-11 5:06 ` K Prateek Nayak
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ZI/x+RkSqpct4bM3@BLR-5CG11610CF.amd.com \
--to=gautham.shenoy@amd.com \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=joshdon@google.com \
--cc=juri.lelli@redhat.com \
--cc=kernel-team@meta.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=roman.gushchin@linux.dev \
--cc=rostedt@goodmis.org \
--cc=tj@kernel.org \
--cc=vincent.guittot@linaro.org \
--cc=void@manifault.com \
--cc=vschneid@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).