block: keep I/O throttling slice time constant

It is not necessary to adjust the slice time at runtime.  We already
extend the current slice in order to carry over accounting into the next
slice.  Changing the actual slice time value introduces oscillations.

The guest may experience large changes in throughput or IOPS from one
moment to the next when slice times are adjusted.

Reported-by: Benoît Canet <benoit@irqsave.net>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-By: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2013-04-05 11:32:20 +02:00 committed by Kevin Wolf
parent 5905fbc9c9
commit ae29d6c64b
3 changed files with 9 additions and 12 deletions

View file

@ -1069,7 +1069,6 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
}
bs->io_limits = io_limits;
bs->slice_time = BLOCK_IO_SLICE_TIME;
if (!bs->io_limits_enabled && bdrv_io_limits_enabled(bs)) {
bdrv_io_limits_enable(bs);