From: Mike Galbraith <efault@gmx.de>
To: Vlastimil Babka <vbabka@suse.cz>,
Frank van der Linden <fvdl@google.com>,
Alexander Krabler <Alexander.Krabler@kuka.com>
Cc: "linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Dennis Schimmel <Dennis.Schimmel@kuka.com>,
Daniel Braunwarth <Daniel.Braunwarth@kuka.com>
Subject: Re: Realtime threads delayed due to kcompactd0
Date: Fri, 01 Aug 2025 04:46:24 +0200 [thread overview]
Message-ID: <026de9fcd4f0ed17c2df95c4f7c56b878a844012.camel@gmx.de> (raw)
In-Reply-To: <71df781c-3ef3-4b26-9ba8-93fc7d4f9eec@suse.cz>
On Thu, 2025-07-31 at 20:41 +0200, Vlastimil Babka wrote:
> On 7/31/25 20:34, Frank van der Linden wrote:
> > Not sure what the right thing to do would be. Either explicitly boost
> > the priority of a thread temporarily during migrate_pages_batch, or
> > mitigate the issue by dealing with 'busy' pages more quickly in
> > migrate_pages_batch.
>
> There's a workaround for realtime tasks. If you mlock[all]() their memory,
> setting sysctl vm.compact_unevictable_allowed to 0 should exclude these
> pages from migration by compaction.
Hm, per documentation that's done automatically for PREEMPT_RT...
On CONFIG_PREEMPT_RT the default value is 0 in order to avoid a page fault, due
to compaction, which would block the task from becoming active until the fault
is resolved.
...but rummaging, seems other stuff can step on it (contiguous alloc?).
-Mike
next prev parent reply other threads:[~2025-08-01 2:46 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-25 5:30 Alexander Krabler
2025-07-31 18:34 ` Frank van der Linden
2025-07-31 18:41 ` Vlastimil Babka
2025-08-01 2:46 ` Mike Galbraith [this message]
2025-08-01 9:58 ` Vlastimil Babka
2025-08-01 11:23 ` Alexander Krabler
2025-08-01 12:57 ` Vlastimil Babka
2025-08-01 13:40 ` Alexander Krabler
2025-08-07 10:48 ` Vlastimil Babka
2025-08-07 12:21 ` Hugh Dickins
2025-08-07 15:49 ` Alexander Krabler
2025-08-08 7:37 ` Vlastimil Babka
2025-08-20 14:29 ` Sebastian Andrzej Siewior
2025-08-01 19:27 ` Frank van der Linden
2025-08-05 14:11 ` Alexander Krabler
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