From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793718117; b=UoZAzSr69jRfuzTxmFu4gUBJJP0GbvLk0VX6UiXsIfr0Nr0YedEVuObFYp212wSYbAj1 4dwoVT7rDuhvXqBVNqCxLERf07pETcqBiF+UJKkbeWxp9wBU2xtq2GMFCtjloWRj17APe jOcq40QYgSoV8yWBQ9R6H6sivlYRzXXQakb5F5SYK26YFe6G0nTHvqLIl3lPnl53spFwv Zz5cs/T0chgNZZKhb4b6gjXaf6G5kA1IvrCj39Hhw8qO+ORn/CSYvxPDPS7NqLPySVY0G JR6WzU6C5h53EtFZprBN8pFMu2DqWsH64HUC7KQmNQG+wDYQFg+md6LNDGmm5sY/BpA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793718117; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=x+DwvzPCizDdWmjSJvWlcQRJydG6oUcS5wV4t674KgA=; b=ATRct9tINwpwLEmTdCTzGKKV5qC0d/FpQeR6bLrKk7KyS3CihJpST1BIots1+YE5PlLy 9oEDejOehhRCAYLvIROfem2A8Gp/o+2nJNKX5OUr9pKTlxOa87pEr9xSvq6Gih3GJj8tj R7rALNsyuzOqYjwkMiSC3Tu37A6jvEATbZ9L6gqK43fyS0Im2Gk9vdmb1mJYU3N3KEnYn CkfJHjuypQonTc7K562v8r8jOlf2xq5TWlfzzxpzGKnQWfVM9lrBoDCYilAOAK4jtBWl4 kaw55T6zLl2eM29QlvtU8EMxvb3gdhxYxlvRd3aM5Dct94yXQzQWAiE89vx1o44trdg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=nt5AkpQ9; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 15CCC606B251; Tue, 3 Nov 2026 15:01:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=nt5AkpQ9 Received: by smtp.kernel.org (Postfix) with ESMTPSA id B751B1F00919; Tue, 3 Nov 2026 15:01:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793718116; bh=x+DwvzPCizDdWmjSJvWlcQRJydG6oUcS5wV4t674KgA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=nt5AkpQ9xzaOQ1fTYw0l5B4HfodCv0sPfD7QFVJnV2c9oEkdAzkw+NTT59o2ggnYz SZbi23+yzLh/v2Wmpx5CcIEUDB/1X8Quo+88j2eLBa7Atfjqeky9v2k319KGMODtCL Ftok0laG7i6piw0fW0Q9jYqWx9uBGsBs0lSJ2yTdHUS+DhfdosZx8g1F1Hs27HmGh0 4IhfI1cku3+T+DlOdPXavAnvm4eVfgYQX/2QigbFcpkT9b//JO6CmCEC6mB6ePeJWt 9zdofkU10cLS6w5myGpOLtx8+RRydr5ein+oH2Hfsg1neaOR7DpSJV2t51KkYE/IPO PMvkXzaCKV5OA== Date: Tue, 3 Nov 2026 05:01:56 -1000 From: Tejun Heo To: Matthew Ruffell Cc: Waiman Long , Frederic Weisbecker , Peter Zijlstra , Ingo Molnar , Andrew Morton , David Hildenbrand , Caron Wills , Ridong Chen , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Jay Vosburgh Subject: Re: [PATCH 0/6] mm, sched, cgroup: LRU Cache never drains when isolcpus are used with spinning SCHED_FIFO tasks causing page migration stalls Message-ID: References: <20261103075940.110308-1-matthew.ruffell@canonical.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261103075940.110308-1-matthew.ruffell@canonical.com> Hello, On Tue, Nov 03, 2026 at 08:59:34PM +1300, Matthew Ruffell wrote: ... > isolcpus=nohz,18-95,108-178 nohz_full=18-95,108-178 rcu_nocbs=18-95,108-178 > rcu_nocb_poll skew_tick=1 nosmt=force idle=poll numa_balancing=disable > transparent_hugepage=never audit=0 nmi_watchdog=0 nowatchdog mce=ignore_ce > tsc=reliable clocksource=tsc We should get rid of fine grained isolation control. This is such a footgun and ties implementation details to interface too tightly. ... > What happens is that the spinning SCHED_FIFO processes running on isolcpus are > constantly dirtying the LRU cache, and when we attempt NUMA migration of the > 50GB of pages, systemd calls flush_migrate_mm_task_workfn() which creates a > kworker that calls cpuset_migrate_mm_workfn() then do_migrate_pages() then > lru_cache_disable(), and then __lru_add_drain_all(). __lru_add_drain_all() then > creates a kworker on each CPU to drain the LRU cache, and systemd and the > initial kworker wait until this is done on all CPUs. I suppose you have fair deadline server disabled? Thanks. -- tejun