On 2022/10/25 15:46, Ziyang Zhang wrote: > 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. > Intel(R) Xeon(R) Platinum 8369B CPU @ 2.70GHz 16 cores 64GB MEM, CentOS 8, kernel 6.0+ with IORING_SETUP_COOP_TASKRUN, without this kernel patch ucmd: io_uring_cmd_complete_in_task(), ublk_drv is a module tw: task_work_add(), ublk is built-in. -------- fio test iodepth=128 numjobs=1 direct=1 bs=4k -------------------------------------------- ublk loop target, the backend is a file. IOPS(k) type ucmd tw seq-read 54.1 53.8 rand-read 52.0 52.0 -------------------------------------------- ublk null target IOPS(k) type ucmd tw seq-read 272 286 rand-read 262 278 ------------ 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 running null/001 fio (ublk/null(), libaio, bs 4k, dio, hw queues:1, uring_comp: 0, get_data: 0)... randwrite: jobs 1, iops 715863 randread: jobs 1, iops 758449 randrw: jobs 1, iops read 357407 write 357183 rw(512k): jobs 1, iops read 5895 write 5875 ------------- tw running loop/001 fio (ublk/loop( -f /root/work/ubdsrv/tests/tmp/ublk_loop_1G_pvLTL), libaio, bs 4k, dio, hw queues:1, uring_comp: 0, get_data: 0)... randwrite: jobs 1, iops 66856 randread: jobs 1, iops 65015 randrw: jobs 1, iops read 32751 write 32767 rw(512k): jobs 1, iops read 776 write 823 running null/001 fio (ublk/null(), libaio, bs 4k, dio, hw queues:1, uring_comp: 0, get_data: 0)... randwrite: jobs 1, iops 739450 randread: jobs 1, iops 787500 randrw: jobs 1, iops read 372956 write 372831 rw(512k): jobs 1, iops read 5798 write 5777
