From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753859AbbJNN1F (ORCPT ); Wed, 14 Oct 2015 09:27:05 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:48750 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753814AbbJNN1C (ORCPT ); Wed, 14 Oct 2015 09:27:02 -0400 Date: Wed, 14 Oct 2015 06:27:00 -0700 From: Christoph Hellwig To: Ming Lin Cc: lkml , Jens Axboe , Kent Overstreet , Dongsu Park , Mike Snitzer , "Martin K. Petersen" , Ming Lin , linux-nvme@lists.infradead.org Subject: Re: [PATCH v6 05/11] block: remove split code in blkdev_issue_{discard,write_same} Message-ID: <20151014132700.GA19401@infradead.org> References: <1439363241-31772-1-git-send-email-mlin@kernel.org> <1439363241-31772-6-git-send-email-mlin@kernel.org> <20151013115011.GA6546@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 13, 2015 at 10:44:11AM -0700, Ming Lin wrote: > I just did a quick test with a Samsung 900G NVMe device. > mkfs.xfs is OK on 4.3-rc5. > > What's your device model? I may find a similar one to try. This is a HGST Ultrastar SN100 Analsys and tentativ fix below: blktrace for before the commit: 259,0 1 2 0.000002543 2394 G D 0 + 8388607 [mkfs.xfs] 259,0 1 3 0.000008230 2394 I D 0 + 8388607 [mkfs.xfs] 259,0 1 4 0.000031090 207 D D 0 + 8388607 [kworker/1:1H] 259,0 1 5 0.000044869 2394 Q D 8388607 + 8388607 [mkfs.xfs] 259,0 1 6 0.000045992 2394 G D 8388607 + 8388607 [mkfs.xfs] 259,0 1 7 0.000049559 2394 I D 8388607 + 8388607 [mkfs.xfs] 259,0 1 8 0.000061551 207 D D 8388607 + 8388607 [kworker/1:1H] .. and so on. blktrace with the commit: 259,0 2 1 0.000000000 1228 Q D 0 + 4194304 [mkfs.xfs] 259,0 2 2 0.000002543 1228 G D 0 + 4194304 [mkfs.xfs] 259,0 2 3 0.000010080 1228 I D 0 + 4194304 [mkfs.xfs] 259,0 2 4 0.000082187 267 D D 0 + 4194304 [kworker/2:1H] 259,0 2 5 0.000224869 1228 Q D 4194304 + 4194304 [mkfs.xfs] 259,0 2 6 0.000225835 1228 G D 4194304 + 4194304 [mkfs.xfs] 259,0 2 7 0.000229457 1228 I D 4194304 + 4194304 [mkfs.xfs] 259,0 2 8 0.000238507 267 D D 4194304 + 4194304 [kworker/2:1H] So discards are smaller, but better aligned. Now if I tweak a single line in blk-lib.c to be able to use all of bi_size I get the old I/O pattern back and everything works fine again: diff --git a/block/blk-lib.c b/block/blk-lib.c index bd40292..65b61dc 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -82,7 +82,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, break; } - req_sects = min_t(sector_t, nr_sects, MAX_BIO_SECTORS); + req_sects = min_t(sector_t, nr_sects, UINT_MAX >> 9); end_sect = sector + req_sects; bio->bi_iter.bi_sector = sector;