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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]:47628 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kLsqK-0007xo-PR for qemu-devel@archiver.kernel.org; Fri, 25 Sep 2020 14:53:16 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54446) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kLspL-0007V0-9d for qemu-devel@nongnu.org; Fri, 25 Sep 2020 14:52:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:51060) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kLspI-00010P-Mw for qemu-devel@nongnu.org; Fri, 25 Sep 2020 14:52:14 -0400 Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601059931; 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: in-reply-to:in-reply-to:references:references; bh=cMxaFPxG1eBNjJ2Be/WPnv7L4OGNxGiFZ8ZERl5Kflc=; b=ePW0R+w+V9CWQ0SbuUGHNGw+LKtNzu2cMHkCHkckgUBoHjrKnzV6+z4Z6U/Q4Q60BBKmsc 47/7Q4opBR+WzwNVGZjx3RsqwrPYmwrk7fZxh75L1mBHffI2Rkxxdn6JS89WJmXGw89Dko xBdkLY8akZkU0fT5Q3X62mhO50jJR68= 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-397-2RDZ81nTNV-OFyc4VdMfSw-1; Fri, 25 Sep 2020 14:52:06 -0400 X-MC-Unique: 2RDZ81nTNV-OFyc4VdMfSw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 22E5D807352; Fri, 25 Sep 2020 18:52:05 +0000 (UTC) Received: from work-vm (ovpn-114-177.ams2.redhat.com [10.36.114.177]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 80C8E7B7A3; Fri, 25 Sep 2020 18:51:49 +0000 (UTC) Date: Fri, 25 Sep 2020 19:51:47 +0100 From: "Dr. David Alan Gilbert" To: Christian Schoenebeck Subject: Re: virtiofs vs 9p performance(Re: tools/virtiofs: Multi threading seems to hurt performance) Message-ID: <20200925185147.GS2873@work-vm> References: <20200918213436.GA3520@redhat.com> <4973513.bp6ERB8pJA@silver> <20200925130538.GK2873@work-vm> <7085634.CctCyd8GvG@silver> MIME-Version: 1.0 In-Reply-To: <7085634.CctCyd8GvG@silver> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/25 02:48:20 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.199, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-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: "Venegas Munoz, Jose Carlos" , qemu-devel@nongnu.org, "cdupontd@redhat.com" , virtio-fs-list , Stefan Hajnoczi , "Shinde, Archana M" , Vivek Goyal Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Christian Schoenebeck (qemu_oss@crudebyte.com) wrote: > On Freitag, 25. September 2020 15:05:38 CEST Dr. David Alan Gilbert wrote: > > > > 9p ( mount -t 9p -o trans=virtio kernel /mnt > > > > -oversion=9p2000.L,cache=mmap,msize=1048576 ) test: (g=0): rw=randrw, > > > > > > Bottleneck ------------------------------^ > > > > > > By increasing 'msize' you would encounter better 9P I/O results. > > > > OK, I thought that was bigger than the default; what number should I > > use? > > It depends on the underlying storage hardware. In other words: you have to try > increasing the 'msize' value to a point where you no longer notice a negative > performance impact (or almost). Which is fortunately quite easy to test on > guest like: > > dd if=/dev/zero of=test.dat bs=1G count=12 > time cat test.dat > /dev/null > > I would start with an absolute minimum msize of 10MB. I would recommend > something around 100MB maybe for a mechanical hard drive. With a PCIe flash > you probably would rather pick several hundred MB or even more. > > That unpleasant 'msize' issue is a limitation of the 9p protocol: client > (guest) must suggest the value of msize on connection to server (host). Server > can only lower, but not raise it. And the client in turn obviously cannot see > host's storage device(s), so client is unable to pick a good value by itself. > So it's a suboptimal handshake issue right now. It doesn't seem to be making a vast difference here: 9p mount -t 9p -o trans=virtio kernel /mnt -oversion=9p2000.L,cache=mmap,msize=104857600 Run status group 0 (all jobs): READ: bw=62.5MiB/s (65.6MB/s), 62.5MiB/s-62.5MiB/s (65.6MB/s-65.6MB/s), io=3070MiB (3219MB), run=49099-49099msec WRITE: bw=20.9MiB/s (21.9MB/s), 20.9MiB/s-20.9MiB/s (21.9MB/s-21.9MB/s), io=1026MiB (1076MB), run=49099-49099msec 9p mount -t 9p -o trans=virtio kernel /mnt -oversion=9p2000.L,cache=mmap,msize=1048576000 Run status group 0 (all jobs): READ: bw=65.2MiB/s (68.3MB/s), 65.2MiB/s-65.2MiB/s (68.3MB/s-68.3MB/s), io=3070MiB (3219MB), run=47104-47104msec WRITE: bw=21.8MiB/s (22.8MB/s), 21.8MiB/s-21.8MiB/s (22.8MB/s-22.8MB/s), io=1026MiB (1076MB), run=47104-47104msec Dave > Many users don't even know this 'msize' parameter exists and hence run with > the Linux kernel's default value of just 8kB. For QEMU 5.2 I addressed this by > logging a performance warning on host side for making users at least aware > about this issue. The long-term plan is to pass a good msize value from host > to guest via virtio (like it's already done for the available export tags) and > the Linux kernel would default to that instead. > > Best regards, > Christian Schoenebeck > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK