From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f200.google.com (mail-qt0-f200.google.com [209.85.216.200]) by kanga.kvack.org (Postfix) with ESMTP id B5BF46B03AD for ; Mon, 26 Jun 2017 08:16:52 -0400 (EDT) Received: by mail-qt0-f200.google.com with SMTP id f92so48245159qtb.4 for ; Mon, 26 Jun 2017 05:16:52 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id 35si2042648qtt.80.2017.06.26.05.16.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Jun 2017 05:16:51 -0700 (PDT) From: Ming Lei Subject: [PATCH v2 24/51] block: blk-merge: try to make front segments in full size Date: Mon, 26 Jun 2017 20:10:07 +0800 Message-Id: <20170626121034.3051-25-ming.lei@redhat.com> In-Reply-To: <20170626121034.3051-1-ming.lei@redhat.com> References: <20170626121034.3051-1-ming.lei@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jens Axboe , Christoph Hellwig , Huang Ying , Andrew Morton , Alexander Viro Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ming Lei When merging one bvec into segment, if the bvec is too big to merge, current policy is to move the whole bvec into another new segment. This patchset changes the policy into trying to maximize size of front segments, that means in above situation, part of bvec is merged into current segment, and the remainder is put into next segment. This patch prepares for support multipage bvec because it can be quite common to see this case and we should try to make front segments in full size. Signed-off-by: Ming Lei --- block/blk-merge.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 49 insertions(+), 5 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index 821b9c206308..bf7a0fa0199f 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -108,6 +108,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, bool do_split = true; struct bio *new = NULL; const unsigned max_sectors = get_max_io_size(q, bio); + unsigned advance = 0; bio_for_each_segment(bv, bio, iter) { /* @@ -133,12 +134,32 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, } if (bvprvp && blk_queue_cluster(q)) { - if (seg_size + bv.bv_len > queue_max_segment_size(q)) - goto new_segment; if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv)) goto new_segment; if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv)) goto new_segment; + if (seg_size + bv.bv_len > queue_max_segment_size(q)) { + /* + * On assumption is that initial value of + * @seg_size(equals to bv.bv_len) won't be + * bigger than max segment size, but will + * becomes false after multipage bvec comes. + */ + advance = queue_max_segment_size(q) - seg_size; + + if (advance > 0) { + seg_size += advance; + sectors += advance >> 9; + bv.bv_len -= advance; + bv.bv_offset += advance; + } + + /* + * Still need to put remainder of current + * bvec into a new segment. + */ + goto new_segment; + } seg_size += bv.bv_len; bvprv = bv; @@ -160,6 +181,12 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, seg_size = bv.bv_len; sectors += bv.bv_len >> 9; + /* restore the bvec for iterator */ + if (advance) { + bv.bv_len += advance; + bv.bv_offset -= advance; + advance = 0; + } } do_split = false; @@ -360,16 +387,29 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, { int nbytes = bvec->bv_len; + unsigned advance = 0; if (*sg && *cluster) { - if ((*sg)->length + nbytes > queue_max_segment_size(q)) - goto new_segment; - if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) goto new_segment; if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) goto new_segment; + /* + * try best to merge part of the bvec into previous + * segment and follow same policy with + * blk_bio_segment_split() + */ + if ((*sg)->length + nbytes > queue_max_segment_size(q)) { + advance = queue_max_segment_size(q) - (*sg)->length; + if (advance) { + (*sg)->length += advance; + bvec->bv_offset += advance; + bvec->bv_len -= advance; + } + goto new_segment; + } + (*sg)->length += nbytes; } else { new_segment: @@ -392,6 +432,10 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); (*nsegs)++; + + /* for making iterator happy */ + bvec->bv_offset -= advance; + bvec->bv_len += advance; } *bvprv = *bvec; } -- 2.9.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org