From patchwork Thu Mar 16 16:02:49 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Lieven X-Patchwork-Id: 9628811 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 885A96048C for ; Thu, 16 Mar 2017 16:04:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7A42028658 for ; Thu, 16 Mar 2017 16:04:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6F1A128676; Thu, 16 Mar 2017 16:04:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 6DF9528658 for ; Thu, 16 Mar 2017 16:04:23 +0000 (UTC) Received: from localhost ([::1]:44584 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1coXsz-0001i4-P7 for patchwork-qemu-devel@patchwork.kernel.org; Thu, 16 Mar 2017 12:04:21 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33272) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1coXrw-00016a-Ga for qemu-devel@nongnu.org; Thu, 16 Mar 2017 12:03:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1coXrs-0000CH-MY for qemu-devel@nongnu.org; Thu, 16 Mar 2017 12:03:16 -0400 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:40046 helo=mx01.kamp.de) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1coXrs-0000AQ-Dy for qemu-devel@nongnu.org; Thu, 16 Mar 2017 12:03:12 -0400 Received: (qmail 15927 invoked by uid 89); 16 Mar 2017 16:03:07 -0000 Received: from [195.62.97.28] by client-16-kamp (envelope-from , uid 89) with qmail-scanner-2010/03/19-MF (clamdscan: 0.99.2/23209. avast: 1.2.2/17010300. spamassassin: 3.4.1. Clear:RC:1(195.62.97.28):. Processed in 0.076172 secs); 16 Mar 2017 16:03:07 -0000 Received: from smtp.kamp.de (HELO submission.kamp.de) ([195.62.97.28]) by mx01.kamp.de with ESMTPS (DHE-RSA-AES256-GCM-SHA384 encrypted); 16 Mar 2017 16:03:05 -0000 X-GL_Whitelist: yes Received: (qmail 14571 invoked from network); 16 Mar 2017 16:03:05 -0000 Received: from lieven-pc.kamp-intra.net (HELO lieven-pc) (relay@kamp.de@::ffff:172.21.12.60) by submission.kamp.de with ESMTPS (DHE-RSA-AES256-GCM-SHA384 encrypted) ESMTPA; 16 Mar 2017 16:03:05 -0000 Received: by lieven-pc (Postfix, from userid 1000) id 7A2FC20472; Thu, 16 Mar 2017 17:03:05 +0100 (CET) From: Peter Lieven To: qemu-devel@nongnu.org Date: Thu, 16 Mar 2017 17:02:49 +0100 Message-Id: <1489680169-7638-1-git-send-email-pl@kamp.de> X-Mailer: git-send-email 1.9.1 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a02:248:0:51::16 Subject: [Qemu-devel] [PATCH for-2.9] thread-pool: add missing qemu_bh_cancel in completion function X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, qemu-block@nongnu.org, stefanha@gmail.com, Peter Lieven , qemu-stable@nongnu.org, pbonzini@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP commit 3c80ca15 fixed a deadlock scenarion with nested aio_poll invocations. However, the rescheduling of the completion BH introcuded unnecessary spinning in the main-loop. On very fast file backends this can even lead to the "WARNING: I/O thread spun for 1000 iterations" message popping up. Callgrind reports about 3-4% less instructions with this patch running qemu-img bench on a ramdisk based VMDK file. Fixes: 3c80ca158c96ff902a30883a8933e755988948b1 Cc: qemu-stable@nongnu.org Signed-off-by: Peter Lieven --- util/thread-pool.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/util/thread-pool.c b/util/thread-pool.c index ce6cd30..610646d 100644 --- a/util/thread-pool.c +++ b/util/thread-pool.c @@ -188,6 +188,13 @@ restart: aio_context_release(pool->ctx); elem->common.cb(elem->common.opaque, elem->ret); aio_context_acquire(pool->ctx); + + /* We can safely cancel the completion_bh here regardless of someone + * else having scheduled it meanwhile because we reenter the + * completion function anyway (goto restart). + */ + qemu_bh_cancel(pool->completion_bh); + qemu_aio_unref(elem); goto restart; } else {