From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87613C433E1 for ; Wed, 19 Aug 2020 14:26:05 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4E7A92076E for ; Wed, 19 Aug 2020 14:26:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="TAzHyBAp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4E7A92076E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=igalia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33614 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8P2S-0002Nl-Hm for qemu-devel@archiver.kernel.org; Wed, 19 Aug 2020 10:26:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43990) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8P1n-0001tc-WB; Wed, 19 Aug 2020 10:25:24 -0400 Received: from fanzine.igalia.com ([178.60.130.6]:41649) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1k8P1l-0008Mn-0w; Wed, 19 Aug 2020 10:25:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Type:MIME-Version:Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From; bh=bmTOdycsi+/DSc9HRJbtzGFxOWXqK4qfIg1yiai7eFw=; b=TAzHyBApXMaAiqJCSVKqjhtYh2yaNASmYkIjCneslwsuwj4EuoDqPad6SMenr31cftINdfhNwvaBe3jnKPUwUPSiatCTt1pEQwSoK5EpkpSWG9RTL9/+S8qQJ8uNSpDJAJM6uGuBpqWDFKKSoUpTuPJPruqNxFGVpF2RZDhNBxhCDlh0sm/k3uDHIw3iC8Qda5WixlaRfbbtgD6thDG4k3eAEgic/uC2eJlLS7P7u4k5FvrwRbe9Szw8zJy3CDriuo56edyMHuKSz936LSsSxedYMFDavxFCfdqFirlclS2FrY4KuentKojuwqiR+hoPeSjUXhZDvM4yWN4QLZwk6A==; Received: from maestria.local.igalia.com ([192.168.10.14] helo=mail.igalia.com) by fanzine.igalia.com with esmtps (Cipher TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim) id 1k8P1h-0007G9-59; Wed, 19 Aug 2020 16:25:17 +0200 Received: from berto by mail.igalia.com with local (Exim) id 1k8P1g-0006eN-Rm; Wed, 19 Aug 2020 16:25:16 +0200 From: Alberto Garcia To: Kevin Wolf Subject: Re: [PATCH 0/1] qcow2: Skip copy-on-write when allocating a zero cluster In-Reply-To: <20200817155307.GS11402@linux.fritz.box> References: <20200817101019.GD11402@linux.fritz.box> <20200817155307.GS11402@linux.fritz.box> User-Agent: Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) Date: Wed, 19 Aug 2020 16:25:16 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=178.60.130.6; envelope-from=berto@igalia.com; helo=fanzine.igalia.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/19 10:25:17 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x (no timestamps) [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon 17 Aug 2020 05:53:07 PM CEST, Kevin Wolf wrote: >> > Or are you saying that ZERO_RANGE + pwrite on a sparse file (= >> > cluster allocation) is faster for you than just the pwrite alone (= >> > writing to already allocated cluster)? >> >> Yes, 20% faster in my tests (4KB random writes), but in the latter >> case the cluster is already allocated only at the qcow2 level, not on >> the filesystem. preallocation=falloc is faster than >> preallocation=metadata (preallocation=off sits in the middle). > > Hm, this feels wrong. Doing more operations should never be faster > than doing less operations. > > Maybe the difference is in allocating 64k at once instead of doing a > separate allocation for every 4k block? But with the extent size hint > patches to file-posix, we should allocate 1 MB at once by default now > (if your test image was newly created). Can you check whether this is > in effect for your image file? I checked with xfs on my computer. I'm not very familiar with that filesystem so I was using the default options and I didn't tune anything. What I got with my tests (using fio): - Using extent_size_hint didn't make any difference in my test case (I do see a clear difference however with the test case described in commit ffa244c84a). - preallocation=off is still faster than preallocation=metadata. If I disable handle_alloc_space() (so there is no ZERO_RANGE used) then it is much slower. - With preallocation=falloc I get the same results as with preallocation=metadata. - preallocation=full is the fastest by far. Berto