On Mon, Jun 21, 2021 at 07:33:34PM +0800, JeffleXu wrote: > > > On 6/18/21 10:39 PM, Ming Lei wrote: > > From 47e523b9ee988317369eaadb96826323cd86819e Mon Sep 17 00:00:00 2001 > > From: Ming Lei <ming.lei@xxxxxxxxxx> > > Date: Wed, 16 Jun 2021 16:13:46 +0800 > > Subject: [RFC PATCH V3 3/3] dm: support bio polling > > > > Support bio(REQ_POLLED) polling in the following approach: > > > > 1) only support io polling on normal READ/WRITE, and other abnormal IOs > > still fallback on IRQ mode, so the target io is exactly inside the dm > > io. > > > > 2) hold one refcnt on io->io_count after submitting this dm bio with > > REQ_POLLED > > > > 3) support dm native bio splitting, any dm io instance associated with > > current bio will be added into one list which head is bio->bi_end_io > > which will be recovered before ending this bio > > > > 4) implement .poll_bio() callback, call bio_poll() on the single target > > bio inside the dm io which is retrieved via bio->bi_bio_drv_data; call > > dec_pending() after the target io is done in .poll_bio() > > > > 4) enable QUEUE_FLAG_POLL if all underlying queues enable QUEUE_FLAG_POLL, > > which is based on Jeffle's previous patch. > > > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> > > --- > > V3: > > - covers all comments from Jeffle > > - fix corner cases when polling on abnormal ios > > > ... > > One bug and one performance issue, though I haven't investigated deep > for both. > > > kernel base: based on Jens' for-next, applying Christoph and Leiming's > patchset. > > > 1. One bug when there's DM device stack, e.g., dm-linear upon another > dm-linear. Can be reproduced by following steps: > > ``` > $ sudo dmsetup create tmpdev --table '0 2097152 linear /dev/nvme0n1 0' > > $ cat tmp.table > 0 2097152 linear /dev/mapper/tmpdev 0 > 2097152 2097152 linear /dev/nvme0n1 0 > > $ cat tmp.table | dmsetup create testdev > > $ fio -name=test -ioengine=io_uring -iodepth=128 -numjobs=1 -thread > -rw=randread -direct=1 -bs=4k -time_based -runtime=10 -cpus_allowed=6 > -filename=/dev/mapper/testdev -hipri=1 > ``` > > > BUG: unable to handle page fault for address: ffffffffc01a6208 > #PF: supervisor write access in kernel mode > #PF: error_code(0x0003) - permissions violation > PGD 39740c067 P4D 39740c067 PUD 39740e067 PMD 1035db067 PTE 1ddf6f061 > Oops: 0003 [#1] SMP PTI > CPU: 6 PID: 5899 Comm: fio Tainted: G S > 5.13.0-0.1.git.81bcdc3.al7.x86_64 #1 > Hardware name: Inventec K900G3-10G/B900G3, BIOS A2.20 06/23/2017 > RIP: 0010:dm_submit_bio+0x171/0x3e0 [dm_mod] > Code: 08 85 c0 0f 84 78 01 00 00 80 7c 24 2c 00 0f 84 b8 00 00 00 48 8b > 53 38 48 8b 44 24 18 48 85 d2 48 8d 48 28 48 89 50 28 74 04 <48> 89 4a > 08 48 89 4b 38 48 83 c3 38 48 89 58 30 41 f7 c5 fe ff ff > RSP: 0018:ffff9e5c45e1b9a0 EFLAGS: 00010286 > RAX: ffff8ab59fd50140 RBX: ffff8ab59fd50088 RCX: ffff8ab59fd50168 > RDX: ffffffffc01a6200 RSI: 0000000000052f08 RDI: 0000000000000000 > RBP: ffff8ab59fd501c8 R08: 0000000000000000 R09: 0000000000000000 > R10: ffff9e5c45e1b950 R11: 0000000000000007 R12: ffff8ab4c2bc2000 > R13: 0000000000000000 R14: ffff8ab4c2bc2548 R15: ffff8ab59fd50140 > FS: 00007f555de42700(0000) GS:ffff8af33f180000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffffffffc01a6208 CR3: 0000000124990005 CR4: 00000000003706e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > submit_bio_noacct+0x144/0x3f0 > ? submit_bio+0x42/0x120 > submit_bio+0x42/0x120 > blkdev_direct_IO+0x454/0x4b0 > ? io_resubmit_prep+0x40/0x40 > ? __fsnotify_parent+0xff/0x350 > ? __fsnotify_parent+0x10f/0x350 > ? generic_file_read_iter+0x83/0x150 > generic_file_read_iter+0x83/0x150 > blkdev_read_iter+0x41/0x50 > io_read+0xe9/0x420 > ? __cond_resched+0x16/0x40 > ? __kmalloc_node+0x16e/0x4e0 > ? memcg_alloc_page_obj_cgroups+0x32/0x90 > ? io_issue_sqe+0x7e8/0x1260 > io_issue_sqe+0x7e8/0x1260 > ? io_submit_sqes+0x47b/0x1420 > __io_queue_sqe+0x56/0x380 > ? io_submit_sqes+0x120a/0x1420 > io_submit_sqes+0x120a/0x1420 > ? __x64_sys_io_uring_enter+0x1d2/0x3e0 > __x64_sys_io_uring_enter+0x1d2/0x3e0 > ? exit_to_user_mode_prepare+0x4c/0x210 > do_syscall_64+0x36/0x70 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x7f55d3cb1b59 > Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 > f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 > f0 ff ff 73 01 c3 48 8b 0d ff e2 2b 00 f7 d8 64 89 01 48 > RSP: 002b:00007f555de41b18 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa > RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f55d3cb1b59 > RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000005 > RBP: 00007f557ce81000 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000001 R11: 0000000000000246 R12: 0000000001276000 > R13: 0000000000000001 R14: 0000000000000000 R15: 00000000012c8328 > > > > > 2. Performance Issue > > I test both on x86 (with only one NVMe) and aarch64 (with multiple NVMes). > > The result (IOPS) on x86 is as expected: > > Type |IRQ | Polling > --------- | ---- | ---- > dm-linear | 239k | 357k > > - dm-linear built upon one NVMe，bs=4k, iopoll=1, iodepth=128, > numjobs=1, direct, randread, ioengine=io_uring > > > > While the result on aarch64 is a little confusing. > > Type |IRQ | Polling > ------------- | ---- | ---- > dm-linear [1] | 208k | 230k > dm-linear [2] | 637k | 691k > dm-stripe | 310k | 354k > > - dm-linear [1] built upon *one* NVMe，bs=4k, iopoll=1, iodepth=128, > *numjobs=1*, direct, randread, ioengine=io_uring > - dm-linear [2] built upon *three* NVMes，bs=4k, iopoll=1, iodepth=128, > *numjobs=3*, direct, randread, ioengine=io_uring > - dm-stripe built upon *three* NVMes，chunk_size=4k, bs=12k, iopoll=1, > iodepth=128, numjobs=3, direct, randread, ioengine=io_uring Today I found the following patch makes a big difference on aarch64 nvme io polling, and you can try that in your test: https://lore.kernel.org/linux-block/YNwfY6kExqJM65+L@T590/T/#m934fabf588d709109fd99040a3e26d7a9838db1f https://lore.kernel.org/linux-block/YNwfY6kExqJM65+L@T590/T/#m4504b01d06566b2080216640625fac5fdd3929e5 BTW, my test machine is ampere(160cores, dual numa nodes). Thanks, Ming
