Re: [PATCH v1 0/2] Add timeout mechanism to qmp actions

[Zhenyu Ye <yezhenyu2@huawei.com>]

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