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Sat, 15 Sep 2018 01:31:41 +0000 Received: from CY4PR21MB0776.namprd21.prod.outlook.com ([fe80::151:b6fe:32c8:cccd]) by CY4PR21MB0776.namprd21.prod.outlook.com ([fe80::151:b6fe:32c8:cccd%9]) with mapi id 15.20.1164.008; Sat, 15 Sep 2018 01:31:41 +0000 From: Sasha Levin To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Ming Lei , Laurence Oberman , Omar Sandoval , Bart Van Assche , Jens Axboe , Sasha Levin Subject: [PATCH AUTOSEL 4.18 87/92] blk-mq: only attempt to merge bio if there is rq in sw queue Thread-Topic: [PATCH AUTOSEL 4.18 87/92] blk-mq: only attempt to merge bio if there is rq in sw queue Thread-Index: AQHUTJO+xsTBxEvFrkS+tytoy+ySqQ== Date: Sat, 15 Sep 2018 01:30:53 +0000 Message-ID: <20180915012944.179481-86-alexander.levin@microsoft.com> References: <20180915012944.179481-1-alexander.levin@microsoft.com> In-Reply-To: <20180915012944.179481-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;CY4PR21MB0117;6:tXiZ4qPy458iOHifaz9ELPrnzGGnr62TuL9vzbfqGntv/Vcs3OYJkwg6j3z6G+iM5lztKBdOuh0b1HG6/uhQDw6TYsEzzAQh4jcELNOEs+Mlwjt7D1OZbbhqENx6LhGBeAa6FXCHCYLOUzGelact+3UbHfpGTkKjfdTDLLVFkM0Nu5HfgtxxWFYNHbI0r1D2AwKcfgb0YDalYPfSdMdwW64MpfxPFqrfsbi1q3vWqRmViyRRgH3ozRTUCQtqXN/Ziy8vVo1edzff6vpnj4vB+zWF1UB8fCPW4DsyyzmSy/PVzz3xK+dcYFdYdtHni2L3uT+ZGtBMyg7hFMzXVcBWrjaOHumaC+dJnzCECpecwDd8j3fCf8MNXQ3D1wL1xgcvlRE3SrckEII9SgDhI376rlkwW+zuxZD0l2Y55jA+BP1tx47W0vbj6ncprCFkRzuDPUfJfDN2L61HtEvpK15j/A==;5:ZEsQAlowYxUT6pY5lpeWFK3JobS/bdHM2oJ+mCO1N4mPtlfG+xxYEIu2xs6pyvf5tWExscwrSqcynQUpd4MoZzKH3Cyg+8MRej/L8cR2ZWi9cebC3YoL0lY5+A6WTaD95GlhY7dl1+8Kt1A0t/9XpTyUi5qu7SjxS7f/uOEPd84=;7:zpai0W7Y/Hxz48I+UJrqyg1MJR6/YsaIjAuYbDZENeRNj6l/6DyWqisAMppNVmwcJ43Es/aHDTxMUeaqIX1WIuxOjBZJnWBmbsTGF7wt+davh0XBK3yzEBpy0RjdoOjJDzTnTCKVLDLZ97yg3i4UPmdcuHdbAa02RFCLqyCjmSAKzYTYkWH5BKBU8EVrBULfypMf0tXvUhR/k44IreKomFU+BHvGDBwqJ8XgzRaBJ7uf3YTxNAsrZR2PI9h/Rdjf x-ms-office365-filtering-correlation-id: bdc23c81-863f-4423-9158-08d61aaafd4e x-ms-office365-filtering-ht: Tenant x-microsoft-antispam: BCL:0;PCL:0;RULEID:(7020095)(4652040)(8989137)(4534165)(4627221)(201703031133081)(201702281549075)(8990107)(5600074)(711020)(4618075)(2017052603328)(7193020);SRVR:CY4PR21MB0117; 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received-spf: None (protection.outlook.com: microsoft.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: tjh39B/RqUEVSIFNeoGVqVeXuJ83OCF83kYAVwo1hmX0DSRlEcXyTs2iLIbEsm3ORltXgQVYxRfHXZuE4Knqgzw4vpsPNqeEBXmCkrnNsyONfskcc8cKm316qVsj8SrV/3gY0+kWmgM29sWns2YJwctMBy1j123KYLrl4tV6xvF4I3yJyFeU2KMa3ygQXxEkddnJSgE3afTbYiIiaotOs/8JtAcTNO1eeCrnTRskCTxNuRIHrtSKooNZcQw4vAOrS4c9mjCcntll4bUAvv1atM6mvH+5LcK80WUKhp1ebCvbxnJeLwPRLCtQKZ0rwpLg9RIqoE6m4NGgpow5S6W8IrYFuzbLjh+w2WSgIYtpfg8= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: bdc23c81-863f-4423-9158-08d61aaafd4e X-MS-Exchange-CrossTenant-originalarrivaltime: 15 Sep 2018 01:30:53.8229 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR21MB0117 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ming Lei [ Upstream commit b04f50ab8a74129b3041a2836c33c916be3c6667 ] Only attempt to merge bio iff the ctx->rq_list isn't empty, because: 1) for high-performance SSD, most of times dispatch may succeed, then there may be nothing left in ctx->rq_list, so don't try to merge over sw queue if it is empty, then we can save one acquiring of ctx->lock 2) we can't expect good merge performance on per-cpu sw queue, and missing one merge on sw queue won't be a big deal since tasks can be scheduled from one CPU to another. Cc: Laurence Oberman Cc: Omar Sandoval Cc: Bart Van Assche Tested-by: Kashyap Desai Reported-by: Kashyap Desai Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-mq-sched.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 56c493c6cd90..f5745acc2d98 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -339,7 +339,8 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, = struct bio *bio) return e->type->ops.mq.bio_merge(hctx, bio); } =20 - if (hctx->flags & BLK_MQ_F_SHOULD_MERGE) { + if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) && + !list_empty_careful(&ctx->rq_list)) { /* default per sw-queue merge */ spin_lock(&ctx->lock); ret =3D blk_mq_attempt_merge(q, ctx, bio); --=20 2.17.1