From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 AC3A33EA98 for ; Wed, 14 May 2025 05:17:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747199874; cv=none; b=LHM3IuOCEEs6CyGv2ymQW2ueHkkVqQ9yReuZVo5quxahxLJi8kq+m1qtWP732zPNG2grVlS5UoDCMLJufvs3uQ6tbsILuIhcsHes8yMbru+FEMqFqOyY7hyBqtCYCZM0u3rsyxxCLnPD7WU2L5pl1xoXY6r5B7pZRIgVOz9972A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747199874; c=relaxed/simple; bh=B8/PYLnIVwapTuCP6BmW6RrckGy6HOia+4hp75e9Px8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WZCQS4kEG7Hqva9kKoD83vlzFA86tP3zncfF6DtZnrSbQ/ecb3UQXjGAdB9RIMVX1wg1NyiGNcJiIcEO8O6WqFHMnqDX3mWSnHRhZtqqtXYs0Ogcu2CHH1W/CbcQAXJsMGoV0gFXDeabEfPgCtPEO98WaYOIZ/9vbBhE1IYYMJU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 798E068AA6; Wed, 14 May 2025 07:17:47 +0200 (CEST) Date: Wed, 14 May 2025 07:17:47 +0200 From: Christoph Hellwig To: Yu Kuai Cc: Christoph Hellwig , xni@redhat.com, colyli@kernel.org, agk@redhat.com, snitzer@kernel.org, mpatocka@redhat.com, song@kernel.org, linux-kernel@vger.kernel.org, dm-devel@lists.linux.dev, linux-raid@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, johnny.chenyi@huawei.com, "yukuai (C)" Subject: Re: [PATCH RFC md-6.16 v3 15/19] md/md-llbitmap: implement APIs to dirty bits and clear bits Message-ID: <20250514051747.GA24503@lst.de> References: <20250512051722.GA1667@lst.de> <0de7efeb-6d4a-2fa5-ed14-e2c0bec0257b@huaweicloud.com> <20250512132641.GC31781@lst.de> <20250512133048.GA32562@lst.de> <69dc5ab6-542d-dcc2-f4ec-0a6a8e49b937@huaweicloud.com> <03f64fc7-4e57-2f32-bffc-04836a9df790@huaweicloud.com> <20250513064803.GA1508@lst.de> <87a53ae0-c4d6-adff-8272-c49d63bf30db@huaweicloud.com> <20250513074304.GA2696@lst.de> Precedence: bulk X-Mailing-List: dm-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) On Tue, May 13, 2025 at 05:32:13PM +0800, Yu Kuai wrote: > I was thinking about record a stack dev depth in mddev to handle the > weird case inside raid. Is there other stack device have the same > problem? AFAIK, some dm targets like dm-crypt are using workqueue > to handle all IO. I guess anything that might have to read in metadata to serve a data I/O. bcache, dm-snapshot and dm-thinkp would be candidates for that, but I haven't checked the implementation. > I'm still interested because this can improve first write latency. > >> >> So instead just write a comment documenting why you switch to a >> different stack using the workqueue. > > Ok, I'll add comment if we keep using the workqueue. Maybe do that for getting the new bitmap code in ASAP and then revisit the above separately?