| Message ID | 1427268446-6426-1-git-send-email-famz@redhat.com |
|---|---|
| State | New |
| Headers | show |
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 <pbonzini@redhat.com> > Reviewed-by: Alberto Garcia <berto@igalia.com> > Signed-off-by: Fam Zheng <famz@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
On Wed, 03/25 15:31, Stefan Hajnoczi wrote: > Queued for QEMU 2.4. Please let me know if you think it's worth risking > adding it in QEMU 2.3. Thanks, 2.4 is okay. Fam
diff --git a/block.c b/block.c index 0fe97de..89a1d5b 100644 --- a/block.c +++ b/block.c @@ -30,6 +30,7 @@ #include "qapi/qmp/qjson.h" #include "sysemu/block-backend.h" #include "sysemu/sysemu.h" +#include "sysemu/qtest.h" #include "qemu/notify.h" #include "block/coroutine.h" #include "block/qapi.h" @@ -181,10 +182,16 @@ static void bdrv_throttle_write_timer_cb(void *opaque) /* should be called before bdrv_set_io_limits if a limit is set */ void bdrv_io_limits_enable(BlockDriverState *bs) { + int clock_type = QEMU_CLOCK_REALTIME; + + if (qtest_enabled()) { + /* For testing block IO throttling only */ + clock_type = QEMU_CLOCK_VIRTUAL; + } assert(!bs->io_limits_enabled); throttle_init(&bs->throttle_state, bdrv_get_aio_context(bs), - QEMU_CLOCK_VIRTUAL, + clock_type, bdrv_throttle_read_timer_cb, bdrv_throttle_write_timer_cb, bs);