Re: [Qemu-devel] [PATCH] iotests: fix 185

[Kevin Wolf]

Am 08.08.2017 um 10:42 hat Vladimir Sementsov-Ogievskiy geschrieben:
> 07.08.2017 18:57, Kevin Wolf wrote:
> > Am 07.08.2017 um 16:16 hat Vladimir Sementsov-Ogievskiy geschrieben:
> > > 185 iotest is broken.
> > > 
> > > How to test:
> > > > i=0; while ./check -qcow2 -nocache 185; do ((i+=1)); echo N = $i; \
> > >    done; echo N = $i
> > > 
> > > finished for me like this:
> > > 
> > > 185 2s ... - output mismatch (see 185.out.bad)
> > > --- /work/src/qemu/master/tests/qemu-iotests/185.out    2017-07-14 \
> > >      15:14:29.520343805 +0300
> > > +++ 185.out.bad 2017-08-07 16:51:02.231922900 +0300
> > > @@ -37,7 +37,7 @@
> > >   {"return": {}}
> > >   {"return": {}}
> > >   {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, \
> > >       "event": "SHUTDOWN", "data": {"guest": false}}
> > > -{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, \
> > >      "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", \
> > >          "len": 4194304, "offset": 4194304, "speed": 65536, "type": \
> > >              "mirror"}}
> > > +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, \
> > >      "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", \
> > >          "len": 0, "offset": 0, "speed": 65536, "type": "mirror"}}
> > > 
> > >   === Start backup job and exit qemu ===
> > > 
> > > Failures: 185
> > > Failed 1 of 1 tests
> > > N = 8
> > > 
> > > It doesn't seems logical to expect the constant offset on cancel,
> > > so let filter it out.
> > > 
> > > Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> > I'm quoting 185:
> > 
> > # Note that the reference output intentionally includes the 'offset' field 
> > in
> > # BLOCK_JOB_CANCELLED events for all of the following block jobs. They are
> > # predictable and any change in the offsets would hint at a bug in the job
> > # throttling code.
> > #
> > # In order to achieve these predictable offsets, all of the following tests
> > # use speed=65536. Each job will perform exactly one iteration before it has
> > # to sleep at least for a second, which is plenty of time for the 'quit' QMP
> > # command to be received (after receiving the command, the rest runs
> > # synchronously, so jobs can arbitrarily continue or complete).
> > #
> > # The buffer size for commit and streaming is 512k (waiting for 8 seconds 
> > after
> > # the first request), for active commit and mirror it's large enough to 
> > cover
> > # the full 4M, and for backup it's the qcow2 cluster size, which we know is
> > # 64k. As all of these are at least as large as the speed, we are sure that 
> > the
> > # offset doesn't advance after the first iteration before qemu exits.
> > 
> > So before we change the expected output, can we explain why the offsets
> > aren't predictable, even if throttling is used and contrary to what the
> > comment says? Should we sleep a little before issuing 'quit'?
> 
> Throttling "guaranties" that there will not be more than one request. But
> what prevent less than one, i.e. zero, like in my reproduction?

Yes, I understand. Can we somehow make sure that at least one iteration
is made? I'd really like to keep the functional test for block job
throttling. I suppose a simple 'sleep 0.1' would do the trick, though
it's not very clean.

Kevin