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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 2F1FBC433E0 for ; Tue, 7 Jul 2020 14:48:31 +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 F2C8C20738 for ; Tue, 7 Jul 2020 14:48:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="P9JqHmW1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F2C8C20738 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:54152 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jsota-0007Dp-90 for qemu-devel@archiver.kernel.org; Tue, 07 Jul 2020 10:48:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39326) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jsosQ-00067Y-8k for qemu-devel@nongnu.org; Tue, 07 Jul 2020 10:47:19 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:54002 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jsosM-0007m0-FE for qemu-devel@nongnu.org; Tue, 07 Jul 2020 10:47:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594133232; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IO343SM0kWitS75vuoEF09RzcVckBgtH67BuOlTr2h0=; b=P9JqHmW1Z4H1P2VCMmvHcb+m9dUUdoub89mXpPaft8sZCiJ3+A4WoufNN80273yj53N3t5 T3tJhB2ZVolSj2XewASKVNM21yDDquWB8la0x9tILcRo1ddu0uNJquuFxMSSSoG3AM+ch/ jhMItUOCr2IZWGHduj43eswqv1KTrYY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-93-UzdBBxiZOwCGbBIFicH0TA-1; Tue, 07 Jul 2020 10:47:08 -0400 X-MC-Unique: UzdBBxiZOwCGbBIFicH0TA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E90CF804003; Tue, 7 Jul 2020 14:47:07 +0000 (UTC) Received: from [10.3.113.97] (ovpn-113-97.phx2.redhat.com [10.3.113.97]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 94D901001901; Tue, 7 Jul 2020 14:47:07 +0000 (UTC) Subject: Re: [PATCH for-5.1] file-posix: Mitigate file fragmentation with extent size hints To: Kevin Wolf , qemu-block@nongnu.org References: <20200707142329.48303-1-kwolf@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <7080e331-fa75-bc5c-1406-e4a772411ea2@redhat.com> Date: Tue, 7 Jul 2020 09:47:06 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200707142329.48303-1-kwolf@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/07 00:20:54 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/7/20 9:23 AM, Kevin Wolf wrote: > Espeically when O_DIRECT is used with image files so that the page cache Especially > indirection can't cause a merge of allocating requests, the file will > fragment on the file system layer, with a potentially very small > fragment size (this depends on the requests the guest sent). > > On Linux, fragmentation can be reduced by setting an extent size hint > when creating the file (at least on XFS, it can't be set any more after > the first extent has been allocated), basically giving raw files a > "cluster size" for allocation. > > This adds an create option to set the extent size hint, and changes the > default from not setting a hint to setting it to 1 MB. The main reason > why qcow2 defaults to smaller cluster sizes is that COW becomes more > expensive, which is not an issue with raw files, so we can choose a > larger file. The tradeoff here is only potentially wasted disk space. > > For qcow2 (or other image formats) over file-posix, the advantage should > even be greater because they grow sequentially without leaving holes, so > there won't be wasted space. Setting even larger extent size hints for > such images may make sense. This can be done with the new option, but > let's keep the default conservative for now. > > The effect is very visible with a test that intentionally creates a > badly fragmented file with qemu-img bench (the time difference while > creating the file is already remarkable) and then looks at the number of > extents and the take a simple "qemu-img map" takes. Cool! > > Signed-off-by: Kevin Wolf > --- > qapi/block-core.json | 11 ++++++---- > include/block/block_int.h | 1 + > block/file-posix.c | 42 +++++++++++++++++++++++++++++++++++++++ > 3 files changed, 50 insertions(+), 4 deletions(-) > > +#ifdef FS_IOC_FSSETXATTR > + /* > + * Try to set the extent size hint. Failure is not fatal, and a warning is > + * only printed if the option was explicitly specified. > + */ > + { > + struct fsxattr attr; > + result = ioctl(fd, FS_IOC_FSGETXATTR, &attr); > + if (result == 0) { > + attr.fsx_xflags |= FS_XFLAG_EXTSIZE; > + attr.fsx_extsize = file_opts->extent_size_hint; > + result = ioctl(fd, FS_IOC_FSSETXATTR, &attr); > + } > + if (result < 0 && file_opts->has_extent_size_hint) { > + warn_report("Failed to set extent size hint: %s", > + strerror(errno)); > + } > + } > +#endif That's a neat ioctl to learn. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org