From patchwork Thu Apr 13 10:45:15 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joseph Salisbury X-Patchwork-Id: 750410 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 3w3crX2B0Xz9s65; Thu, 13 Apr 2017 20:45:32 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1cycFd-0005Bb-AD; Thu, 13 Apr 2017 10:45:21 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1cycFZ-0005BP-1W for kernel-team@lists.ubuntu.com; Thu, 13 Apr 2017 10:45:17 +0000 Received: from 1.general.jsalisbury.us.vpn ([10.172.67.212] helo=vp9) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1cycFY-0003Vp-L0 for kernel-team@lists.ubuntu.com; Thu, 13 Apr 2017 10:45:16 +0000 Received: by vp9 (Postfix, from userid 1000) id A53E4603C7; Thu, 13 Apr 2017 06:45:15 -0400 (EDT) From: Joseph Salisbury To: kernel-team@lists.ubuntu.com Subject: [SRU][Xenial][Yakkety][PATCH 1/1] block: relax check on sg gap Date: Thu, 13 Apr 2017 06:45:15 -0400 Message-Id: <29eb85e07efa8d2d360aa0ab952bff050a85ead5.1492026266.git.joseph.salisbury@canonical.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: References: In-Reply-To: References: X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com From: Ming Lei BugLink: http://bugs.launchpad.net/bugs/1682215 If the last bvec of the 1st bio and the 1st bvec of the next bio are physically contigious, and the latter can be merged to last segment of the 1st bio, we should think they don't violate sg gap(or virt boundary) limit. Both Vitaly and Dexuan reported lots of unmergeable small bios are observed when running mkfs on Hyper-V virtual storage, and performance becomes quite low. This patch fixes that performance issue. The same issue should exist on NVMe, since it sets virt boundary too. Reported-by: Vitaly Kuznetsov Reported-by: Dexuan Cui Tested-by: Dexuan Cui Cc: Keith Busch Signed-off-by: Ming Lei Signed-off-by: Jens Axboe (cherry picked from commit 729204ef49ec00b788ce23deb9eb922a5769f55d) Signed-off-by: Joseph Salisbury Acked-by: Colin Ian King Acked-by: Seth Forshee --- include/linux/blkdev.h | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index f28a95a..a0b6aae 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1387,6 +1387,25 @@ static inline bool bvec_gap_to_prev(struct request_queue *q, return __bvec_gap_to_prev(q, bprv, offset); } +/* + * Check if the two bvecs from two bios can be merged to one segment. + * If yes, no need to check gap between the two bios since the 1st bio + * and the 1st bvec in the 2nd bio can be handled in one segment. + */ +static inline bool bios_segs_mergeable(struct request_queue *q, + struct bio *prev, struct bio_vec *prev_last_bv, + struct bio_vec *next_first_bv) +{ + if (!BIOVEC_PHYS_MERGEABLE(prev_last_bv, next_first_bv)) + return false; + if (!BIOVEC_SEG_BOUNDARY(q, prev_last_bv, next_first_bv)) + return false; + if (prev->bi_seg_back_size + next_first_bv->bv_len > + queue_max_segment_size(q)) + return false; + return true; +} + static inline bool bio_will_gap(struct request_queue *q, struct bio *prev, struct bio *next) { @@ -1396,7 +1415,8 @@ static inline bool bio_will_gap(struct request_queue *q, struct bio *prev, bio_get_last_bvec(prev, &pb); bio_get_first_bvec(next, &nb); - return __bvec_gap_to_prev(q, &pb, nb.bv_offset); + if (!bios_segs_mergeable(q, prev, &pb, &nb)) + return __bvec_gap_to_prev(q, &pb, nb.bv_offset); } return false;