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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 5825BC4727C for ; Fri, 25 Sep 2020 15:52:39 +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 B7CB421741 for ; Fri, 25 Sep 2020 15:52:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b="h2bq8Guj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B7CB421741 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=crudebyte.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:43684 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kLq1V-0005kR-Om for qemu-devel@archiver.kernel.org; Fri, 25 Sep 2020 11:52:37 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:37724) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kLpwY-00015a-9L for qemu-devel@nongnu.org; Fri, 25 Sep 2020 11:47:33 -0400 Received: from lizzy.crudebyte.com ([91.194.90.13]:39521) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kLpwU-0000E7-BR for qemu-devel@nongnu.org; Fri, 25 Sep 2020 11:47:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Content-Type:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Content-ID:Content-Description; bh=F6mcedIpg5w876yARFX2BeCE/zuKLgBW/YTc2xMOwYs=; b=h2bq8GujGL2lRk3oXTBBG8LRo8 YxCYpUvZ4nmv7Bq1Vx88aab5lfs2CqRroM8CqZkZBUW/gsAYArsiWo0BZIIsDf5+AH2o5QuO+7RZ1 /k7SMz0jYc8w83BOc2syySLFu2zCRQ/9+qvUzRghQwSaZiIq4Zb8IEyW7rJ+grsyMvaW+J9AgM6bv hA5UW6G+nNchQej3TCia3nnFTk7ldZ3V98OINeZRo9OpSaIPfvO7NO56EXRaMIvd/RypOLJmBWhHr sTOqVnJN+XI7ut2FKRW30mQbbau/2H8ne7kclMNWYLNgSoQ7iE0RcN7rY+dOUI1rtxC2Uf4sKfnsq yLpTKUPQ==; From: Christian Schoenebeck To: qemu-devel@nongnu.org Cc: Vivek Goyal , "Shinde, Archana M" , "Venegas Munoz, Jose Carlos" , "Dr. David Alan Gilbert" , virtio-fs-list , Greg Kurz , Stefan Hajnoczi , "cdupontd@redhat.com" Subject: Re: virtiofs vs 9p performance Date: Fri, 25 Sep 2020 17:47:21 +0200 Message-ID: <4615316.mGufCYyPMH@silver> In-Reply-To: <20200925131356.GD132653@redhat.com> References: <20200918213436.GA3520@redhat.com> <17216624.eqST2d0sUl@silver> <20200925131356.GD132653@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Received-SPF: pass client-ip=91.194.90.13; envelope-from=qemu_oss@crudebyte.com; helo=lizzy.crudebyte.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/25 11:47:23 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [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 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Freitag, 25. September 2020 15:13:56 CEST Vivek Goyal wrote: > On Fri, Sep 25, 2020 at 10:06:41AM +0200, Christian Schoenebeck wrote: > > On Freitag, 25. September 2020 00:10:23 CEST Vivek Goyal wrote: > > > In my testing, with cache=none, virtiofs performed better than 9p in > > > all the fio jobs I was running. For the case of cache=auto for virtiofs > > > (with xattr enabled), 9p performed better in certain write workloads. I > > > have identified root cause of that problem and working on > > > HANDLE_KILLPRIV_V2 patches to improve WRITE performance of virtiofs > > > with cache=auto and xattr enabled. > > > > Please note, when it comes to performance aspects, you should set a > > reasonable high value for 'msize' on 9p client side: > > https://wiki.qemu.org/Documentation/9psetup#msize > > Interesting. I will try that. What does "msize" do? Simple: it's the "maximum message size" ever to be used for communication between host and guest, in both directions that is. So if that 'msize' value is too small, a potential large 9p message would be split into several smaller 9p messages, and each message adds latency which is the main problem. Keep in mind: The default value with Linux clients for msize is still only 8kB! Think of doing 'dd bs=8192 if=/src.dat of=/dst.dat count=...' as analogy, which probably makes its impact on performance clear. However the negative impact of a small 'msize' value is not just limited to raw file I/O like that; calling readdir() for instance on a guest directory with several hundred files or more, will likewise slow down in the same way tremendously as both sides have to transmit a large amount of 9p messages back and forth instead of just 2 messages (Treaddir and Rreaddir). > > I'm also working on performance optimizations for 9p BTW. There is plenty > > of headroom to put it mildly. For QEMU 5.2 I started by addressing > > readdir requests: > > https://wiki.qemu.org/ChangeLog/5.2#9pfs > > Nice. I guess this performance comparison between 9p and virtiofs is good. > Both the projects can try to identify weak points and improve performance. Yes, that's indeed handy being able to make comparisons. Best regards, Christian Schoenebeck