From patchwork Sun Jul 19 13:43:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Schoenebeck X-Patchwork-Id: 277727 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=-4.1 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 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 B98CBC433E0 for ; Sun, 19 Jul 2020 14:42:07 +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 830562080D for ; Sun, 19 Jul 2020 14:42:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b="meTzvAwD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 830562080D 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]:33994 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jxAVy-0005Rm-Rb for qemu-devel@archiver.kernel.org; Sun, 19 Jul 2020 10:42:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40178) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jxAVM-0004wc-Mh for qemu-devel@nongnu.org; Sun, 19 Jul 2020 10:41:28 -0400 Received: from lizzy.crudebyte.com ([91.194.90.13]:35909) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jxAVI-0005OK-EK for qemu-devel@nongnu.org; Sun, 19 Jul 2020 10:41:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Cc:To:Subject:Date:From:Message-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Content-ID: Content-Description; bh=qUnVgMmJwCCmefD8hN6aBd1Wz6oGOT8goAe+C5cdzkw=; b=meTzv AwDU43nLnONwBGZwQ8njJqAaaGTzMnJG2mWK2DaQzH7TLeql6RtrLvBlgBW++5ZhBt5q7FJNdlKKq T+ILpAGJynspmI2EomNuH2LspQX2ElUyIZDTOwdsoIhzKt8QmAzKy6YsRlkm0Q+yiVaCeSBWKQgym JU4R1qanWru5oez3x2yS3hdvTr4VGYBTXZEbPZ1mj4jGEaVqefojzMEjBco5gm4uCrtB/EPrBr/28 UKc6g8sKEaakcYndDOt5xJIUroPHd75gFz8L4NTpc3qd5n2NiL7IdsecrnMtO4zESn46L/GWaMMEr TeCk1KYpcZbzzYmYSMOv4m4Uzhr2A==; Message-Id: From: Christian Schoenebeck Date: Sun, 19 Jul 2020 15:43:47 +0200 Subject: [PATCH v7 0/6] 9pfs: readdir optimization To: qemu-devel@nongnu.org Cc: Greg Kurz Received-SPF: none client-ip=91.194.90.13; envelope-from=cb67ffe2c8e5bddc31511d62a859cebfda0b7feb@lizzy.crudebyte.com; helo=lizzy.crudebyte.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/19 10:12:15 X-ACL-Warn: Detected OS = Linux 3.11 and newer 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_NONE=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: , 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 are 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 optimization is patch 4. v6->v7: * Rebased to master: SHA-1 b442119329 * Handle directory seeking more consistently by doing it in do_readdir_many() instead of in v9fs_readdir() [patch 3], [patch 4]. * Updated API doc on v9fs_co_readdir_many(): make it clear that v9fs_free_dirents() must always be called, including error cases [patch 3]. * New patch: use different lock type for 9p2000.u vs. 9p2000.L [patch 5]. Unchanged patches: [patch 1], [patch 2], [patch 6]. Message-ID of previous version (v6): cover.1587309014.git.qemu_oss@crudebyte.com Message-ID of version with performance benchmark (v4): cover.1579567019.git.qemu_oss@crudebyte.com Christian Schoenebeck (6): tests/virtio-9p: added split readdir tests 9pfs: make v9fs_readdir_response_size() public 9pfs: add new function v9fs_co_readdir_many() 9pfs: T_readdir latency optimization 9pfs: differentiate readdir lock between 9P2000.u vs. 9P2000.L 9pfs: clarify latency of v9fs_co_run_in_worker() hw/9pfs/9p.c | 144 ++++++++++++------------- hw/9pfs/9p.h | 50 ++++++++- hw/9pfs/codir.c | 196 +++++++++++++++++++++++++++++++++-- hw/9pfs/coth.h | 15 ++- tests/qtest/virtio-9p-test.c | 108 +++++++++++++++++++ 5 files changed, 419 insertions(+), 94 deletions(-)