Hi, When using hybrid polling (i.e echo 0 > /sys/block/nvme1n1/queue/io_poll_delay) I see stalls with fio when using an iodepth > 1. Sometimes fio hangs, other times the performance is really poor. I reproduced this with SSDs from different vendors. $ echo -1 | sudo tee /sys/block/nvme1n1/queue/io_poll_delay $ fio --ioengine io_uring --rw write --filesize 1GB --overwrite=1 --name=test --direct=1 --bs=$((1024*4)) --time_based=1 --runtime=10 --hipri --iodepth 1 93.4k iops $ fio --ioengine io_uring --rw write --filesize 1GB --overwrite=1 --name=test --direct=1 --bs=$((1024*4)) --time_based=1 --runtime=10 --hipri --iodepth 32 426k iops $ echo 0 | sudo tee /sys/block/nvme1n1/queue/io_poll_delay $ fio --ioengine io_uring --rw write --filesize 1GB --overwrite=1 --name=test --direct=1 --bs=$((1024*4)) --time_based=1 --runtime=10 --hipri --iodepth 1 94.3k iops $ fio --ioengine io_uring --rw write --filesize 1GB --overwrite=1 --name=test --direct=1 --bs=$((1024*4)) --time_based=1 --runtime=10 --hipri --iodepth 32 167 iops fio took 33s However, if I ask fio / io_uring to perform all those IOs at once, the performance is pretty decent again (but obviously that's not that desirable) $ fio --ioengine io_uring --rw write --filesize 1GB --overwrite=1 --name=test --direct=1 --bs=$((1024*4)) --time_based=1 --runtime=10 --hipri --iodepth 32 --iodepth_batch_submit=32 --iodepth_batch_complete_min=32 394k iops So it looks like there's something wrong around tracking what needs to be polled for in hybrid mode. Greetings, Andres Freund
