From: Valentin Schneider <vschneid@redhat.com>
To: Frederic Weisbecker <frederic@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Michal Hocko <mhocko@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org
Subject: Re: [PATCH 4/6] tick/nohz: Move nohz_full related fields out of hot task struct's places
Date: Thu, 17 Jul 2025 18:32:26 +0200 [thread overview]
Message-ID: <xhsmh4ivag4md.mognet@vschneid-thinkpadt14sgen2i.remote.csb> (raw)
In-Reply-To: <20250703140717.25703-5-frederic@kernel.org>
On 03/07/25 16:07, Frederic Weisbecker wrote:
> nohz_full is a feature that only fits into rare and very corner cases.
> Yet distros enable it by default and therefore the related fields are
> always reserved in the task struct.
>
> Those task fields are stored in the middle of cacheline hot places such
> as cputime accounting and context switch counting, which doesn't make
> any sense for a feature that is disabled most of the time.
>
> Move the nohz_full storage to colder places.
>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
task_struct is still a bloody maze to me, but AFAICT there's *at least one*
full non-optional cacheline - the signal handling faff - between cputime
accounting and this new location, so:
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
next prev parent reply other threads:[~2025-07-17 16:32 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-03 14:07 [PATCH 0/6 v4] sched/mm: LRU drain flush on nohz_full Frederic Weisbecker
2025-07-03 14:07 ` [PATCH 1/6] task_work: Provide means to check if a work is queued Frederic Weisbecker
2025-07-03 14:07 ` [PATCH 2/6] sched/fair: Use task_work_queued() on numa_work Frederic Weisbecker
2025-07-03 14:07 ` [PATCH 3/6] sched: Use task_work_queued() on cid_work Frederic Weisbecker
2025-07-17 16:32 ` Valentin Schneider
2025-07-03 14:07 ` [PATCH 4/6] tick/nohz: Move nohz_full related fields out of hot task struct's places Frederic Weisbecker
2025-07-17 16:32 ` Valentin Schneider [this message]
2025-07-03 14:07 ` [PATCH 5/6] sched/isolation: Introduce isolated task work Frederic Weisbecker
2025-07-17 17:29 ` Vlastimil Babka
2025-07-18 9:52 ` Valentin Schneider
2025-07-18 14:23 ` Frederic Weisbecker
2025-07-03 14:07 ` [PATCH 6/6] mm: Drain LRUs upon resume to userspace on nohz_full CPUs Frederic Weisbecker
2025-07-03 14:24 ` Michal Hocko
2025-07-03 14:28 ` Matthew Wilcox
2025-07-03 16:12 ` Michal Hocko
2025-07-17 19:33 ` Vlastimil Babka
-- strict thread matches above, loose matches on Subject: below --
2025-04-10 15:23 [PATCH 0/6 v3] sched/mm: LRU drain flush on nohz_full Frederic Weisbecker
2025-04-10 15:23 ` [PATCH 4/6] tick/nohz: Move nohz_full related fields out of hot task struct's places Frederic Weisbecker
2025-04-23 18:40 ` Shrikanth Hegde
2025-07-01 12:17 ` Frederic Weisbecker
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