Re: [Cluster-devel] [PATCH V15 00/18] block: support multi-page bvec
On Fri, Feb 15, 2019 at 03:51:26PM +0100, Christoph Hellwig wrote: > I still don't understand why mp_bvec_last_segment isn't simply > called bvec_last_segment as there is no conflict. But I don't > want to hold this series up on that as there only are two users > left and we can always just fix it up later. mp_bvec_last_segment() is one bvec helper, so better to keep its name consistent with other bvec helpers. Thanks, Ming
Re: [Cluster-devel] [dm-devel] [PATCH V15 00/18] block: support multi-page bvec
On Fri, Feb 15, 2019 at 09:14:15AM -0800, 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 > 0020 > [ 475.621188] #PF error: [normal kernel read fault] > [ 475.623148] PGD 0 P4D 0 > [ 475.624737] Oops: [#1] PREEMPT SMP KASAN > [ 475.626628] CPU: 1 PID: 277 Comm: kworker/1:1H Tainted: GB > 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) > 0x816a152e 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) > > Bart. Thanks for your test! The following patch should fix this issue: diff --git a/block/blk-merge.c b/block/blk-merge.c index bed065904677..066b66430523 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -363,13 +363,15 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, struct bio_vec bv, bvprv = { NULL }; int prev = 0; unsigned int seg_size, nr_phys_segs; - unsigned front_seg_size = bio->bi_seg_front_size; + unsigned front_seg_size; struct bio *fbio, *bbio; struct bvec_iter iter; if (!bio) return 0; + front_seg_size = bio->bi_seg_front_size; + switch (bio_op(bio)) { case REQ_OP_DISCARD: case REQ_OP_SECURE_ERASE: Thanks, Ming
Re: [Cluster-devel] [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 > > 0020 > > [ 475.621188] #PF error: [normal kernel read fault] > > [ 475.623148] PGD 0 P4D 0 > > [ 475.624737] Oops: [#1] PREEMPT SMP KASAN > > [ 475.626628] CPU: 1 PID: 277 Comm: kworker/1:1H Tainted: GB > > 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) > > 0x816a152e 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
Re: [Cluster-devel] [dm-devel] [PATCH V15 00/18] block: support multi-page bvec
On Sun, Feb 17, 2019 at 09:13:32PM +0800, Ming Lei wrote: > 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 > > > 0020 > > > [ 475.621188] #PF error: [normal kernel read fault] > > > [ 475.623148] PGD 0 P4D 0 > > > [ 475.624737] Oops: [#1] PREEMPT SMP KASAN > > > [ 475.626628] CPU: 1 PID: 277 Comm: kworker/1:1H Tainted: GB > > > 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) > > > 0x816a152e 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. Looks this performance drop isn't reproduced on null_blk with the following setting by me: - modprobe null_blk nr_devices=4 submit_queues=48 - test machine : dual socket, two NUMA nodes, 24cores/socket - fio script: fio --direct=1 --size=128G --bsrange=4k-4k --runtime=40 --numjobs=48 --ioengine=libaio --iodepth=64 --group_reporting=1 --filename=/dev/nullb0 --name=randread --rw=randread result: 10.7M IOPS(base kernel), 10.6M IOPS(patched kernel) And if 'bs' is increased to 256k, 512k, 1024k, IOPS improvement can be ~8% with multi-page bvec patches in above test. BTW, there isn't cost added to bio_for_each_bvec(), so blk_queue_split() and blk_rq_map_sg() should be fine. However, bio_for_each_segment_all() may not be quick as before. Thanks, Ming