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 2D54B15E97 for ; Mon, 30 Mar 2026 19:16:25 +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=1774898186; cv=none; b=N9WyK37LrJmg9aKAaU4aEzmyEBgUd871TC5KGaXo80HQlkzf0QyYVpVp/AuqefrHK22xjsptO2pNhl3LN0jhjATI+iLHEG1vQVm92K1FLrKk0OUFCPt9cdV5kC1yUctDWfUj+v8Yn5xbzaN8m28l0sJoy9dFT8oRNqapcL9mGAA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774898186; c=relaxed/simple; bh=oXQolb1yAb0DgfmX0q35ABD3ZFnm55kI9pf0oMncHE8=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=oKu0cPgnBfTOa4kbKtz3ua3Co76cgEtxcAFH/XVXY2IBaGTnG93BwLG+R+PDdA1pQV1pe+1bhlZzgYLEYFcW5kgY0giJIdxIcHlpAqwIIWKpnLCPUQ+JHTkbP4ooubKlGkXRx/WCW70dlCFMsWAGqzwDfLYQ1Z3mhEl+vkoyoZ8= 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=wNT35w/v; 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="wNT35w/v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9871C4CEF7; Mon, 30 Mar 2026 19:16:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1774898185; bh=oXQolb1yAb0DgfmX0q35ABD3ZFnm55kI9pf0oMncHE8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=wNT35w/vw8xWsD/40fdXn5qc9f0rBOKnU6X48i8mSooOyOfijeLu3kEYts46pIyKe ei6FPh3502BrQiCMZOvAc7esofUiL4PysrOwbE1Qw4vhTO24C2li4kwdUnNSzkRC1r taTbKOXEtY28t2ZBhhL+VepThvLN2OnPxzQSIpEI= Date: Mon, 30 Mar 2026 12:16:25 -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: <20260330121625.c69f46a63c86c9540b823398@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. AI review flagged a couple of possible issues. Do they look real to you? https://sashiko.dev/#/patchset/20260330175824.2777270-1-urezki@gmail.com