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Tue, 31 Mar 2026 02:39:08 -0700 (PDT) Received: from milan ([2001:9b1:d5a0:a500::24b]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-38c835b0946sm20380921fa.0.2026.03.31.02.39.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Mar 2026 02:39:07 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 31 Mar 2026 11:39:06 +0200 To: Andrew Morton Cc: "Uladzislau Rezki (Sony)" , linux-mm@kvack.org, Baoquan He , LKML , lirongqing Subject: Re: [PATCH v2] mm/vmalloc: Use dedicated unbound workqueue for vmap purge/drain Message-ID: References: <20260330175824.2777270-1-urezki@gmail.com> <20260330121625.c69f46a63c86c9540b823398@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260330121625.c69f46a63c86c9540b823398@linux-foundation.org> X-Rspamd-Queue-Id: 21AA4160006 X-Stat-Signature: icdu4ce7fdxahpk4hxc9azu7xbcjrimp X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1774949949-889 X-HE-Meta: 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 Xh4kfAzT 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 30, 2026 at 12:16:25PM -0700, Andrew Morton wrote: > 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. AI review flagged a couple of possible issues. Do they look > real to you? > https://sashiko.dev/#/patchset/20260330175824.2777270-1-urezki@gmail.com > I think the problem about itself locking if running by rescue thread is a valid concern. I will address this. I think the easiest is to use two UNBOUND queues one for master/main thread and second for helpers which reclaim if there are too many objects so the help is needed. I will work on v3. Thank you for review! -- Uladzislau Rezki