From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E78791C3F02; Thu, 20 Mar 2025 07:08:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742454503; cv=none; b=V5vaRprPvfgjEg/nT2NWuE/3PMffkrJFkb+FV6pB8dqb8oZL7bzu9sWTNduewGjgXBTgOfjYj/1ZPOxiabFi8xXXYEDFeLgwvBSK62m0XJc0QPk/Mf+SymoXxV7FFBPCSLrj7h4fErJTTnYbN5QdmQZMTTjKj6Ruojn2aqfjSuQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742454503; c=relaxed/simple; bh=W+9m4XEehGdKldYYVEGbIC6F/LyBFoLsNvRrssBfmkA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aAl3SRwwIrl8482+lWRO6dDny8Ma+tsQhmCPn5TXn2q8cvqpqLWoURY7/7aKY6CMV9rmYkGCvbTwQwX7xK7xW54NORC32FEqdp/FHYQwMGZ1iAx+uqi7FwOM+9v77Uss1e3bsVGBFWjWcBR0ShYK61nNVmXvLFHx50ffc/1dieY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Lfi9GVUP; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Lfi9GVUP" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Z1vSfJUNPkSiRaWMFL7kD4jilYBU0XwUxXLmUH1EUDc=; b=Lfi9GVUP7J0+CSIvCCEI9YBvDt NG6+M1wHsK5fW6nYH7D2gxkPlwi047ytsQs+KDdovgDNmsr2Flg5NrwjefXdwJbX6OaELW7/Hidyi MMbR2kuyVXC+jSPCKCTb/cCP6Ur/fXK/rcD7eb5CIe7EfTWum142o0rFFw1n4t+ZTT3g0jSQ7r6tw QNNAmQQfubgOKceoh+S9i/9OvaTREuTx6yvgxJMbmjqSQE/zWR+CgbpB85vF31YwbnRdlcogymNc+ HRLXr9FWGHDaOzs0wVso0L4veyVaP/pBK8yQxTXWpF5jUQp52yVY/VNsxDAj+yqrTHvNNWT+k3AMD hZoEy8MQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tvA0q-0000000BMyY-05jV; Thu, 20 Mar 2025 07:08:20 +0000 Date: Thu, 20 Mar 2025 00:08:19 -0700 From: Christoph Hellwig To: Ming Lei Cc: Christoph Hellwig , Dave Chinner , Mikulas Patocka , Jens Axboe , Jooyung Han , Alasdair Kergon , Mike Snitzer , Heinz Mauelshagen , zkabelac@redhat.com, dm-devel@lists.linux.dev, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org Subject: Re: [PATCH] the dm-loop target Message-ID: References: <7b8b8a24-f36b-d213-cca1-d8857b6aca02@redhat.com> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Mar 18, 2025 at 05:34:28PM +0800, Ming Lei wrote: > On Tue, Mar 18, 2025 at 12:57:17AM -0700, Christoph Hellwig wrote: > > On Tue, Mar 18, 2025 at 03:27:48PM +1100, Dave Chinner wrote: > > > Yes, NOWAIT may then add an incremental performance improvement on > > > top for optimal layout cases, but I'm still not yet convinced that > > > it is a generally applicable loop device optimisation that everyone > > > wants to always enable due to the potential for 100% NOWAIT > > > submission failure on any given loop device..... > > NOWAIT failure can be avoided actually: > > https://lore.kernel.org/linux-block/20250314021148.3081954-6-ming.lei@redhat.com/ That's a very complex set of heuristics which doesn't match up with other uses of it. > > > > > Yes, I think this is a really good first step: > > > > 1) switch loop to use a per-command work_item unconditionally, which also > > has the nice effect that it cleans up the horrible mess of the > > per-blkcg workers. (note that this is what the nvmet file backend has > > It could be worse to take per-command work, because IO handling crosses > all system wq worker contexts. So do other workloads with pretty good success. > > > always done with good result) > > per-command work does burn lots of CPU unnecessarily, it isn't good for > use case of container That does not match my observations in say nvmet. But if you have numbers please share them.