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Message-ID: <20190217131332.GC7296@ming.t460p> Date: Sun, 17 Feb 2019 21:13:33 +0800 From: Ming Lei <ming.lei@...hat.com> To: Jens Axboe <axboe@...nel.dk> Cc: Bart Van Assche <bvanassche@....org>, Mike Snitzer <snitzer@...hat.com>, linux-mm@...ck.org, dm-devel@...hat.com, Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, "Darrick J . Wong" <darrick.wong@...cle.com>, Omar Sandoval <osandov@...com>, cluster-devel@...hat.com, linux-ext4@...r.kernel.org, Kent Overstreet <kent.overstreet@...il.com>, Boaz Harrosh <ooo@...ctrozaur.com>, Gao Xiang <gaoxiang25@...wei.com>, Coly Li <colyli@...e.de>, linux-raid@...r.kernel.org, Bob Peterson <rpeterso@...hat.com>, linux-bcache@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>, Dave Chinner <dchinner@...hat.com>, David Sterba <dsterba@...e.com>, linux-block@...r.kernel.org, Theodore Ts'o <tytso@....edu>, linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org Subject: Re: [dm-devel] [PATCH V15 00/18] block: support multi-page bvec On Fri, Feb 15, 2019 at 10:59:47AM -0700, Jens Axboe wrote: > On 2/15/19 10:14 AM, Bart Van Assche wrote: > > On Fri, 2019-02-15 at 08:49 -0700, Jens Axboe wrote: > >> On 2/15/19 4:13 AM, Ming Lei wrote: > >>> This patchset brings multi-page bvec into block layer: > >> > >> Applied, thanks Ming. Let's hope it sticks! > > > > Hi Jens and Ming, > > > > Test nvmeof-mp/002 fails with Jens' for-next branch from this morning. > > I have not yet tried to figure out which patch introduced the failure. > > Anyway, this is what I see in the kernel log for test nvmeof-mp/002: > > > > [ 475.611363] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 > > [ 475.621188] #PF error: [normal kernel read fault] > > [ 475.623148] PGD 0 P4D 0 > > [ 475.624737] Oops: 0000 [#1] PREEMPT SMP KASAN > > [ 475.626628] CPU: 1 PID: 277 Comm: kworker/1:1H Tainted: G B 5.0.0-rc6-dbg+ #1 > > [ 475.630232] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 > > [ 475.633855] Workqueue: kblockd blk_mq_requeue_work > > [ 475.635777] RIP: 0010:__blk_recalc_rq_segments+0xbe/0x590 > > [ 475.670948] Call Trace: > > [ 475.693515] blk_recalc_rq_segments+0x2f/0x50 > > [ 475.695081] blk_insert_cloned_request+0xbb/0x1c0 > > [ 475.701142] dm_mq_queue_rq+0x3d1/0x770 > > [ 475.707225] blk_mq_dispatch_rq_list+0x5fc/0xb10 > > [ 475.717137] blk_mq_sched_dispatch_requests+0x256/0x300 > > [ 475.721767] __blk_mq_run_hw_queue+0xd6/0x180 > > [ 475.725920] __blk_mq_delay_run_hw_queue+0x25c/0x290 > > [ 475.727480] blk_mq_run_hw_queue+0x119/0x1b0 > > [ 475.732019] blk_mq_run_hw_queues+0x7b/0xa0 > > [ 475.733468] blk_mq_requeue_work+0x2cb/0x300 > > [ 475.736473] process_one_work+0x4f1/0xa40 > > [ 475.739424] worker_thread+0x67/0x5b0 > > [ 475.741751] kthread+0x1cf/0x1f0 > > [ 475.746034] ret_from_fork+0x24/0x30 > > > > (gdb) list *(__blk_recalc_rq_segments+0xbe) > > 0xffffffff816a152e is in __blk_recalc_rq_segments (block/blk-merge.c:366). > > 361 struct bio *bio) > > 362 { > > 363 struct bio_vec bv, bvprv = { NULL }; > > 364 int prev = 0; > > 365 unsigned int seg_size, nr_phys_segs; > > 366 unsigned front_seg_size = bio->bi_seg_front_size; > > 367 struct bio *fbio, *bbio; > > 368 struct bvec_iter iter; > > 369 > > 370 if (!bio) > > Just ran a few tests, and it also seems to cause about a 5% regression > in per-core IOPS throughput. Prior to this work, I could get 1620K 4k > rand read IOPS out of core, now I'm at ~1535K. The cycler stealer seems > to be blk_queue_split() and blk_rq_map_sg(). Could you share us your test setting? I will run null_blk first and see if it can be reproduced. Thanks, Ming
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