On Wed, Mar 25, 2015 at 03:27:26PM +0800, Fam Zheng wrote: > Currently, throttle timers won't make any progress when VCPU is not > running, which would stall the request queue in utils, qtest, vm > suspending, and live migration, without special handling. > > Block jobs are confusingly inconsistent between with and without > throttling: if user sets a bps limit, stops the vm, then start a block > job, the block job will not make any progress; in contrary, if user > unsets the bps limit, or if it's not set, the block job will run > normally. > > After this patch, with the host clock, even if the VCPUs are stopped, > the throttle queues will be processed. > > This patch also enables potential to add throttle to bdrv_drain_all. > Currently all requests are drained immediately. In other words whenever > it is called, IO throttling goes ineffective (examples: system reset, > migration and many block job operations.). This is a loophole that guest > could exploit. If we use the host clock, we can later just trust the > nested poll. This could be done on top. > > Note that for qemu-iotests case 093, which uses qtest, we still keep vm > clock so the script can control the clock stepping in order to be > deterministic. > > Reviewed-by: Paolo Bonzini <pbonz...@redhat.com> > Reviewed-by: Alberto Garcia <be...@igalia.com> > Signed-off-by: Fam Zheng <f...@redhat.com> > > --- > v4: Fix the description. [Alberto] > v3: More justification in commit message. [Stefan] > Add Paolo's and Alberto's rev-bys. > v2: Don't break qemu-iotests 093. > --- > block.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-)
Queued for QEMU 2.4. Please let me know if you think it's worth risking adding it in QEMU 2.3. Thanks, applied to my block-next tree: https://github.com/stefanha/qemu/commits/block-next Stefan
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