Re: [Qemu-devel] [PATCH v4 1/1] Make qemu_peek_buffer loop until it gets it's data

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* ???? (chenliang0016@icloud.com) wrote:
> 
> > * ???? (chenliang0016@icloud.com) wrote:
> >> 
> >>> * ???? (chenliang0016@icloud.com) wrote:
> >>>> 
> >>>> ?? 2014??4??8????????10:29??Dr. David Alan Gilbert (git) <dgilbert@redhat.com> ??????
> >>>> 
> >>>>> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >>>>> 
> >>>>> Make qemu_peek_buffer repeatedly call fill_buffer until it gets
> >>>>> all the data it requires, or until there is an error.
> >>>>> 
> >>>>> At the moment, qemu_peek_buffer will try one qemu_fill_buffer if there
> >>>>> isn't enough data waiting, however the kernel is entitled to return
> >>>>> just a few bytes, and still leave qemu_peek_buffer with less bytes
> >>>>> than it needed.  I've seen this fail in a dev world, and I think it
> >>>>> could theoretically fail in the peeking of the subsection headers in
> >>>>> the current world.
> >>>> hmm, I also have got some errors(infrequently). Maybe It is one point.
> >>>> Could you show some messages about the error?
> >>> 
> >>> I've only seen the errors in my visitor/ber world where I use the peek_buffer
> >>> a lot more; but the one place it is used in the existing code is in
> >>> the code to check if we have the start of a subsection; if that goes wrong
> >>> I'm not sure what error would be produced.
> >>> 
> >>> Dave
> >> In my observation, error is more likely to happen if migration thread is blocked too long.
> >> BTW, xbzrle and auto convergence are disable.
> > 
> > What error do you see?
> > 
> > Dave
> It likes section id 1 load failed at dest side.

Our migration errors aren't particularly descriptive :-(
However, try it with this patch - I'd be interested if it makes
your problem go away.

Dave
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK