On 2022/10/25 15:19, Ming Lei wrote: > On Tue, Oct 25, 2022 at 11:15:57AM +0800, Ziyang Zhang wrote: >> 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. > > The difference is just how batching is handled, looks blk-mq's batch info > doesn't matter any more. In my test, looks the perf improvement is mainly > made by enabling IORING_SETUP_COOP_TASKRUN in ublksrv. I guess only IORING_SETUP_COOP_TASKRUN helps improve IOPS. The llist in ublk_drv does not improve IOPS. > > Can you check if enabling IORING_SETUP_COOP_TASKRUN only can reach > same perf with task_work_add()(ublk_drv is builtin) when building > ublk_drv as module? > OK. Regards, Zhang
