From: Michal Hocko <mhocko@suse.com>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Valentin Schneider <vschneid@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [RFC PATCH 6/6] mm: Drain LRUs upon resume to userspace on nohz_full CPUs
Date: Tue, 25 Jun 2024 16:20:01 +0200 [thread overview]
Message-ID: <ZnrSEf1xuFxKxj1D@tiehlicka> (raw)
In-Reply-To: <20240625135244.20227-7-frederic@kernel.org>
On Tue 25-06-24 15:52:44, Frederic Weisbecker wrote:
> LRUs can be drained through several ways. One of them may add disturbances
> to isolated workloads while queuing a work at any time to any target,
> whether running in nohz_full mode or not.
>
> Prevent from that on isolated tasks with draining LRUs upon resuming to
> userspace using the isolated task work framework.
>
> It's worth noting that this is inherently racy against
> lru_add_drain_all() remotely queueing the per CPU drain work and
> therefore it prevents from the undesired disturbance only
> *most of the time*.
Can we simply not schedule flushing on remote CPUs and leave that to the
"return to the userspace" path?
I do not think we rely on LRU cache flushing for correctness purposes anywhere.
Please also CC linux MM ML once the core infrastructure is agreed on.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2024-06-25 14:20 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-25 13:52 [RFC PATCH 0/6] mm: LRU drain flush on nohz_full Frederic Weisbecker
2024-06-25 13:52 ` [RFC PATCH 1/6] task_work: Provide means to check if a work is queued Frederic Weisbecker
2024-06-25 14:15 ` Oleg Nesterov
2024-06-25 15:16 ` Oleg Nesterov
2024-07-03 12:42 ` Frederic Weisbecker
2024-07-03 12:41 ` Frederic Weisbecker
2024-07-16 13:00 ` Valentin Schneider
2024-06-25 13:52 ` [RFC PATCH 2/6] sched/fair: Use task_work_queued() on numa_work Frederic Weisbecker
2024-07-16 13:00 ` Valentin Schneider
2024-06-25 13:52 ` [RFC PATCH 3/6] sched: Use task_work_queued() on cid_work Frederic Weisbecker
2024-07-16 13:00 ` Valentin Schneider
2024-06-25 13:52 ` [RFC PATCH 4/6] tick/nohz: Move nohz_full related fields out of hot task struct's places Frederic Weisbecker
2024-06-25 13:52 ` [RFC PATCH 5/6] sched/isolation: Introduce isolated task work Frederic Weisbecker
2024-06-26 13:27 ` Vlastimil Babka
2024-07-03 12:47 ` Frederic Weisbecker
2024-06-25 13:52 ` [RFC PATCH 6/6] mm: Drain LRUs upon resume to userspace on nohz_full CPUs Frederic Weisbecker
2024-06-25 14:20 ` Michal Hocko [this message]
2024-06-26 13:16 ` Vlastimil Babka
2024-06-27 6:54 ` Michal Hocko
2024-07-03 12:52 ` Frederic Weisbecker
2024-07-04 13:11 ` Michal Hocko
2024-07-17 13:21 ` Frederic Weisbecker
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