From patchwork Mon Mar 20 23:08:45 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Roth X-Patchwork-Id: 741341 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3vnCkQ6B2Tz9s7B for ; Tue, 21 Mar 2017 11:05:18 +1100 (AEDT) Received: from localhost ([::1]:35808 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cq7Ia-0007CY-C0 for incoming@patchwork.ozlabs.org; Mon, 20 Mar 2017 20:05:16 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42088) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cq6RC-0002Ds-9Y for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:10:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cq6R0-0005NW-Vl for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:10:06 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:38784) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cq6R0-0005MX-Mv for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:54 -0400 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v2KN8g19020995 for ; Mon, 20 Mar 2017 19:09:53 -0400 Received: from e13.ny.us.ibm.com (e13.ny.us.ibm.com [129.33.205.203]) by mx0a-001b2d01.pphosted.com with ESMTP id 299yqc6yyr-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Mar 2017 19:09:53 -0400 Received: from localhost by e13.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 20 Mar 2017 19:09:50 -0400 Received: from b01ledav03.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v2KN9pjk38535170; Mon, 20 Mar 2017 23:09:51 GMT Received: from b01ledav03.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 338C5B204E; Mon, 20 Mar 2017 19:09:46 -0400 (EDT) Received: from localhost (unknown [9.53.92.194]) by b01ledav03.gho.pok.ibm.com (Postfix) with ESMTP id 2287DB2054; Mon, 20 Mar 2017 19:09:46 -0400 (EDT) From: Michael Roth To: qemu-devel@nongnu.org Date: Mon, 20 Mar 2017 18:08:45 -0500 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1490051325-3770-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1490051325-3770-1-git-send-email-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17032023-0008-0000-0000-000001CF4035 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006819; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000206; SDB=6.00836553; UDB=6.00411161; IPR=6.00614322; BA=6.00005224; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014732; XFM=3.00000013; UTC=2017-03-20 23:09:51 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17032023-0009-0000-0000-000033FD6323 Message-Id: <1490051325-3770-82-git-send-email-mdroth@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-03-20_16:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1703200196 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.156.1 Subject: [Qemu-devel] [PATCH 81/81] 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: Kevin Wolf , Peter Lieven , qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Peter Lieven 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 Signed-off-by: Kevin Wolf (cherry picked from commit b7a745dc33a18377bb4a8dfe54d1df01ea60bf66) * drop context dep on b9e413d Signed-off-by: Michael Roth --- thread-pool.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/thread-pool.c b/thread-pool.c index 6fba913..4157210 100644 --- a/thread-pool.c +++ b/thread-pool.c @@ -185,6 +185,13 @@ restart: qemu_bh_schedule(pool->completion_bh); elem->common.cb(elem->common.opaque, elem->ret); + + /* 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 {