On 8/26/21 9:49 PM, Damien Le Moal wrote: > So the mq-deadline priority patch reduces performance by nearly half at high QD. > With the modified patch, we are back to better numbers, but still a significant > 20% drop at high QD. Hi Damien, An implementation of I/O priority for the deadline scheduler that reduces the IOPS drop to 1% on my test setup is available here: https://github.com/bvanassche/linux/tree/block-for-next > (*) Note: in all cases using the mq-deadline scheduler, for the first run at > QD=1, I get this splat 100% of the time. > > [ 95.173889] watchdog: BUG: soft lockup - CPU#0 stuck for 26s! [kworker/0:1H:757] > [ 95.292994] CPU: 0 PID: 757 Comm: kworker/0:1H Not tainted 5.14.0-rc7+ #1334 > [ 95.307504] Workqueue: kblockd blk_mq_run_work_fn > [ 95.312243] RIP: 0010:_raw_spin_unlock_irqrestore+0x35/0x40 > [ 95.415904] Call Trace: > [ 95.418373] try_to_wake_up+0x268/0x7c0 > [ 95.422238] blk_update_request+0x25b/0x420 > [ 95.426452] blk_mq_end_request+0x1c/0x120 > [ 95.430576] null_handle_cmd+0x12d/0x270 [null_blk] > [ 95.435485] blk_mq_dispatch_rq_list+0x13c/0x7f0 > [ 95.443826] __blk_mq_do_dispatch_sched+0xb5/0x2f0 > [ 95.448653] __blk_mq_sched_dispatch_requests+0xf4/0x140 > [ 95.453998] blk_mq_sched_dispatch_requests+0x30/0x60 > [ 95.459083] __blk_mq_run_hw_queue+0x49/0x90 > [ 95.463377] process_one_work+0x26c/0x570 > [ 95.467421] worker_thread+0x55/0x3c0 > [ 95.475313] kthread+0x140/0x160 > [ 95.482774] ret_from_fork+0x1f/0x30 I don't see any function names in the above call stack that refer to the mq-deadline scheduler? Did I perhaps overlook something? Anyway, if you can tell me how to reproduce this (kernel commit + kernel config) I will take a look. Thanks, Bart.
