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b=ysBOI21wYxD8GcrME0utq+cQKbiY/9J62YP2177Wdqkv4Zro3jL97Kln2IraAHMIQ SU07hUqLBBLBxMYJ80zFoVkRoLYItJIfEG7EEURAJ59c86VON1R9cCTltAlSJvYyyk n6h84lxLYfOJrd29vIweJRw3JbuPCu8QYNauJNiE= Date: Mon, 30 Mar 2026 11:56:18 -0700 From: Andrew Morton To: "Uladzislau Rezki (Sony)" Cc: linux-mm@kvack.org, Baoquan He , LKML , lirongqing Subject: Re: [PATCH v2] mm/vmalloc: Use dedicated unbound workqueue for vmap purge/drain Message-Id: <20260330115618.62fb0d6bdf89cedd453035d0@linux-foundation.org> In-Reply-To: <20260330175824.2777270-1-urezki@gmail.com> References: <20260330175824.2777270-1-urezki@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: wtwcosfppwchihf9rbiz4puyzfees6p6 X-Rspamd-Queue-Id: 8BF4D40007 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1774896980-175334 X-HE-Meta: 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 oYJQPwoZ +mgLFwhezWe3KEMtj9jqqRmvXv1hTmpb6Qnk2BC9k0cNpJZzQmvzLRH+UtugNzr6tMGH+s3JR2ExwazOepCRp7xjiD7Ggg6gEYUK69MmuZk64FZvdGt/lCSY+sxA+LFGJq9o2GeBK5VE/6iPRo49EhJBcej+9ovUXprNu+5qelPuVpOJyi+rNKBTPweT9copQPtBaZf8eEtcOoNb1E8mLDYygDABdNHR9qLixlBnYzENwK1TlWkbaIX+pHLO3cmQWDIRZ2ZNTLmnwBw+79pYUETTUhRh0xqF201C7H1FUFgkBAJAqTZ+NeKAyfL9vvfVkgJRn Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 30 Mar 2026 19:58:24 +0200 "Uladzislau Rezki (Sony)" wrote: > The drain_vmap_area_work() function can take >10ms to complete > when there are many accumulated vmap areas in a system with a > high CPU count, causing workqueue watchdog warnings when run > via schedule_work(): > > [ 2069.796205] workqueue: drain_vmap_area_work hogged CPU for >10000us 4 times, consider switching to WQ_UNBOUND > [ 2192.823225] workqueue: drain_vmap_area_work hogged CPU for >10000us 5 times, consider switching to WQ_UNBOUND > > Switch to a dedicated WQ_UNBOUND workqueue to allow the scheduler to > run this background task on any available CPU, improving responsiveness. > Use WQ_MEM_RECLAIM to ensure forward progress under memory pressure. > > If queuing work to the dedicated workqueue is not possible(during > early boot), fall back to processing locally to avoid losing progress. > > Also simplify purge helper scheduling by removing cpumask-based > iteration in favour to iterating directly over vmap nodes with > pending work. Thanks, both. > Cc: lirongqing > Link: https://lore.kernel.org/all/20260319074307.2325-1-lirongqing@baidu.com/ > Signed-off-by: Uladzislau Rezki (Sony) We don't want to be scaring our users with kernel warnings. Do you think a Fixes: or cc:stable are justified? And I wonder if that workqueue warning should be WARN_ON_ONCE. That would mean that other, later call sites wouldn't get the report, but we'll still get to hear about those callsites from someone else.