On 8/30/2017 4:54 PM, Alberto Garcia wrote:
On Wed 30 Aug 2017 02:10:53 PM CEST, Pradeep Jagadeesh wrote:
I'm trying to read from an 9p share that has limits set with hmp
fsdev_set_io_throttle and I'm having some problems.
Here's one simple way to reproduce it:
1) Launch qemu with
-fsdev local,security_model=none,id=fs0,path=/some/files
-device virtio-9p-pci,fsdev=fs0,mount_tag=fs0
2) In the guest, mount the fs0 share in /mnt
3) Run this hmp command
fsdev_set_io_throttle fs0 0 4096 0 0 0 0
4) In the guest, start reading some large file from the 9p share:
dd if=/mnt/large_file of=/dev/null bs=4k iflag=direct status=progress
5) Check the progress, reading speed should be around 4k per second.
6) While dd is still running, change the I/O limits:
fsdev_set_io_throttle fs0 0 8192 0 0 0 0
7) If you check the status of the dd command, reading should be faster
now. Instead, it is stalled.
Thanks for the steps, I did reproduce the issue easily.
Looking into the code, may be we also need to try the same with the
block devices.
-Pradeep
Berto