From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B7F352ECEAE for ; Mon, 30 Mar 2026 18:56:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774896979; cv=none; b=RO5kW8qeWrFeS28IL5zR4Jgmel1MnledqMzkVIoqdEFiwjvfIioLB+iHtr/xKCNsUzEuKENFUBhPpITlEe4cyHCoFRvwIK+7ZLCNI0yNMf0MW2/BrkoY0RU5cQe0vXlKv8la8qh67subxttw23IZUEBJyWoU/NSprWFiBpHdh/U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774896979; c=relaxed/simple; bh=59JFEL/6YtbWchuoZOYX4CjEHVV67PqkA6uWzpMcbEk=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=pJkARH1CbCuUXmkhtWEFkbqsnrgGnqtmW/ntQCJmC7UeIu+SUEdgZp1ny38llLHQVecqKoNsjEJsOe9aNXbaOy7wpxToVmmAqQqDavpXHElSv6GhMLvUg9C5Ua/X/z6/cIMLshLKOT4XqFANTni9Wpg3tGCTpaZj58+L/ETFzG4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=ysBOI21w; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="ysBOI21w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2775FC4CEF7; Mon, 30 Mar 2026 18:56:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1774896979; bh=59JFEL/6YtbWchuoZOYX4CjEHVV67PqkA6uWzpMcbEk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; 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) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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.