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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 C6CDFC43603 for ; Wed, 18 Dec 2019 15:11:37 +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 8FA832146E for ; Wed, 18 Dec 2019 15:11:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b="ew1nyq9n" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8FA832146E 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]:55492 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ihazA-00070J-N1 for qemu-devel@archiver.kernel.org; Wed, 18 Dec 2019 10:11:36 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47114) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ihayF-0005zw-Aj for qemu-devel@nongnu.org; Wed, 18 Dec 2019 10:10:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ihayC-0007jD-K4 for qemu-devel@nongnu.org; Wed, 18 Dec 2019 10:10:38 -0500 Received: from lizzy.crudebyte.com ([91.194.90.13]:41569) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ihayC-0001jF-AC for qemu-devel@nongnu.org; Wed, 18 Dec 2019 10:10:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Subject:Date:Cc:To:From:Message-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Content-ID: Content-Description; bh=xB5nDUai3x8uOUkmS81PvHKbTLLxkdWC5+Wpk/EGVoE=; b=ew1ny q9nI7IxnXpz6OCDbOadD9BClX6/fxGXhjrN4kMu+yKF4X10Vy3sKqxDKWNbTRlsvK3IjHjM4aXHWu 9xUsaBIeo8aRvwBfD5wdsGTJLaXptsP+OlXeuGCm0cvC85XBJAuLWLeTG5+JQC92iuYb0ukTCLfcM E72nLKf6vw+10PjFb9VB5Br2Rge/suJD/yLmSD5fjZj00E/se9cQBVTxXRCPPsdWDf248EkGmdcNp wNfyfJiaU3ukknOdA82xIfg9qSbDqH+5VJaVYMZWEa7MV2kFb6/dpKVRa4ndrhv5/8lsSR4Q08fuH JiUjAsL2unbWmJYwcZKKi94YKq1YA==; Message-Id: From: Christian Schoenebeck To: qemu-devel@nongnu.org Cc: Greg Kurz Date: Wed, 18 Dec 2019 15:17:24 +0100 Subject: [PATCH v2 0/9] 9pfs: readdir optimization X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 91.194.90.13 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" As previously mentioned, I was investigating performance issues with 9pfs. Raw file read/write of 9pfs is actually quite good, provided that client picked a reasonable high msize (maximum message size). I would recommend to log a warning on 9p server side if a client attached with a small msize that would cause performance issues for that reason. However there other aspects where 9pfs currently performs suboptimally, especially readdir handling of 9pfs is extremely slow, a simple readdir request of a guest typically blocks for several hundred milliseconds or even several seconds, no matter how powerful the underlying hardware is. The reason for this performance issue: latency. Currently 9pfs is heavily dispatching a T_readdir request numerous times between main I/O thread and a background I/O thread back and forth; in fact it is actually hopping between threads even multiple times for every single directory entry during T_readdir request handling which leads in total to huge latencies for a single T_readdir request. This patch series aims to address this severe performance issue of 9pfs T_readdir request handling. The actual performance fix is patch 8. I also provided a convenient benchmark for comparing the performance improvements by using the 9pfs "synth" driver (see patch 6 for instructions how to run the benchmark), so no guest OS installation is required to peform this benchmark A/B comparison. With patch 8 I achieved a performance improvement of factor 40 on my test machine. ** NOTE: ** These patches are not heavily tested yet, nor thouroughly reviewed for potential security issues yet. I decided to post them already though, because I won't have the time in the next few weeks for polishing them. The benchmark results should demonstrate though that it is worth the hassle. So any testing/reviews/fixes appreciated! v1->v2: * Fixed missing email threading of this patch set. * Fixed code style issues. * No need to check for NULL when calling g_free() [patch 4] and [patch 8]. * No need to initialize static variable with NULL [patch 7]. * Adjustments to commit log messages. Christian Schoenebeck (9): tests/virtio-9p: add terminating null in v9fs_string_read() 9pfs: validate count sent by client with T_readdir hw/9pfs/9p-synth: added directory for readdir test tests/virtio-9p: added readdir test tests/virtio-9p: check file names of R_readdir response 9pfs: readdir benchmark hw/9pfs/9p-synth: avoid n-square issue in synth_readdir() 9pfs: T_readdir latency optimization hw/9pfs/9p.c: benchmark time on T_readdir request hw/9pfs/9p-synth.c | 48 ++++++++++- hw/9pfs/9p-synth.h | 5 ++ hw/9pfs/9p.c | 151 ++++++++++++++++++--------------- hw/9pfs/9p.h | 23 +++++ hw/9pfs/codir.c | 183 +++++++++++++++++++++++++++++++++++++--- hw/9pfs/coth.h | 3 + tests/virtio-9p-test.c | 186 ++++++++++++++++++++++++++++++++++++++++- 7 files changed, 516 insertions(+), 83 deletions(-) -- 2.20.1