On 2020/10/19 21:25, Paolo Bonzini wrote: > On 19/10/20 14:40, Zhenyu Ye wrote: >> The kernel backtrace for io_submit in GUEST is: >> >> guest# ./offcputime -K -p `pgrep -nx fio` >> b'finish_task_switch' >> b'__schedule' >> b'schedule' >> b'io_schedule' >> b'blk_mq_get_tag' >> b'blk_mq_get_request' >> b'blk_mq_make_request' >> b'generic_make_request' >> b'submit_bio' >> b'blkdev_direct_IO' >> b'generic_file_read_iter' >> b'aio_read' >> b'io_submit_one' >> b'__x64_sys_io_submit' >> b'do_syscall_64' >> b'entry_SYSCALL_64_after_hwframe' >> - fio (1464) >> 40031912 >> >> And Linux io_uring can avoid the latency problem. > > What filesystem are you using? >
On host, the VM image and disk images are based on ext4 filesystem. In guest, the '/' uses xfs filesystem, and the disks are raw devices. guest# df -hT Filesystem Type Size Used Avail Use% Mounted on devtmpfs devtmpfs 16G 0 16G 0% /dev tmpfs tmpfs 16G 0 16G 0% /dev/shm tmpfs tmpfs 16G 976K 16G 1% /run /dev/mapper/fedora-root xfs 8.0G 3.2G 4.9G 40% / tmpfs tmpfs 16G 0 16G 0% /tmp /dev/sda1 xfs 1014M 181M 834M 18% /boot tmpfs tmpfs 3.2G 0 3.2G 0% /run/user/0 guest# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 10G 0 disk ├─sda1 8:1 0 1G 0 part /boot └─sda2 8:2 0 9G 0 part ├─fedora-root 253:0 0 8G 0 lvm / └─fedora-swap 253:1 0 1G 0 lvm [SWAP] vda 252:0 0 10G 0 disk vdb 252:16 0 10G 0 disk vdc 252:32 0 10G 0 disk vdd 252:48 0 10G 0 disk Thanks, Zhenyu
