On 2022/10/24 21:20, Ming Lei wrote: > Hello Ziyang, > > On Mon, Oct 24, 2022 at 05:48:51PM +0800, Ziyang Zhang wrote: >> On 2022/10/23 17:38, Ming Lei wrote: >>> task_work_add() is used for waking ubq daemon task with one batch >>> of io requests/commands queued. However, task_work_add() isn't >>> exported for module code, and it is still debatable if the symbol >>> should be exported. >>> >>> Fortunately we still have io_uring_cmd_complete_in_task() which just >>> can't handle batched wakeup for us. >>> >>> Add one one llist into ublk_queue and call io_uring_cmd_complete_in_task() >>> via current command for running them via task work. >>> >>> This way cleans up current code a lot, meantime allow us to wakeup >>> ubq daemon task after queueing batched requests/io commands. >>> >> >> >> Hi, Ming >> >> This patch works and I have run some tests to compare current version(ucmd) >> with your patch(ucmd-batch). >> >> iodepth=128 numjobs=1 direct=1 bs=4k >> >> -------------------------------------------- >> ublk loop target, the backend is a file. >> IOPS(k) >> >> type ucmd ucmd-batch >> seq-read 54.7 54.2 >> rand-read 52.8 52.0 >> >> -------------------------------------------- >> ublk null target >> IOPS(k) >> >> type ucmd ucmd-batch >> seq-read 257 257 >> rand-read 252 253 >> >> >> I find that io_req_task_work_add() puts task_work node into a llist >> first, then it may call task_work_add() to run batched task_works. So do we really >> need such llist in ublk_drv? I think io_uring has already considered task_work batch >> optimization. >> >> BTW, task_work_add() in ublk_drv achieves >> higher IOPS(about 5-10% on my machine) than io_uring_cmd_complete_in_task() >> in ublk_drv. > > Yeah, that is same with my observation, and motivation of this patch is > to get same performance with task_work_add by building ublk_drv as > module. One win of task_work_add() is that we get exact batching info > meantime only send TWA_SIGNAL_NO_IPI for whole batch, that is basically > what the patch is doing, but needs help of the following ublksrv patch: > > https://github.com/ming1/ubdsrv/commit/dce6d1d222023c1641292713b311ced01e6dc548 > > which sets IORING_SETUP_COOP_TASKRUN for ublksrv's uring, then > io_uring_cmd_complete_in_task will notify via TWA_SIGNAL_NO_IPI, and 5+% > IOPS boost is observed on loop/001 by putting image on SSD in my test > VM. Hi Ming, I have added this ublksrv patch and run the above test again. I have also run ublksrv test: loop/001. Please check them. Intel(R) Xeon(R) Platinum 8369B CPU @ 2.70GHz 16 cores 64GB MEM, CentOS 8, kernel 6.0+ -------- fio test iodepth=128 numjobs=1 direct=1 bs=4k ucmd: without your kernel patch. Run io_uring_cmd_complete_in_task() for each blk-mq rq. ucmd-batch: with your kernel patch. Run io_uring_cmd_complete_in_task() for the last blk-mq rq. -------------------------------------------- ublk loop target, the backend is a file. IOPS(k) type ucmd ucmd-batch seq-read 54.1 53.7 rand-read 52.0 52.0 -------------------------------------------- ublk null target IOPS(k) type ucmd ucmd-batch seq-read 272 265 rand-read 262 260 ------------ ublksrv test ------------- ucmd running loop/001 fio (ublk/loop( -f /root/work/ubdsrv/tests/tmp/ublk_loop_1G_BZ85U), libaio, bs 4k, dio, hw queues:1, uring_comp: 0, get_data: 0)... randwrite: jobs 1, iops 66737 randread: jobs 1, iops 64935 randrw: jobs 1, iops read 32694 write 32710 rw(512k): jobs 1, iops read 772 write 819 ------------- ucmd-batch running loop/001 fio (ublk/loop( -f /root/work/ubdsrv/tests/tmp/ublk_loop_1G_F56a3), libaio, bs 4k, dio, hw queues:1, uring_comp: 0, get_data: 0)... randwrite: jobs 1, iops 66720 randread: jobs 1, iops 65015 randrw: jobs 1, iops read 32743 write 32759 rw(512k): jobs 1, iops read 771 write 817 It seems that manually putting rqs into llist and calling io_uring_cmd_complete_in_task() while handling the last rq does not improve IOPS much. io_req_task_work_add() puts task_work node into a internal llist first, then it may call task_work_add() to run batched task_works. IMO, io_uring has already done such batch optimization and ublk_drv does not need to add such llist. Regards, Zhang.
