Re: [Qemu-devel] [PATCH v5 7/7] Use qemu_put_buffer_async for guest memory pages

[Kevin Wolf]

Am 05.04.2013 um 17:23 hat Paolo Bonzini geschrieben:
> Il 05/04/2013 15:44, Kevin Wolf ha scritto:
> > This seems to have killed savevm performance. I noticed that
> > qemu-iotests case 007 took forever on my test box (882 seconds instead
> > of something like 10 seconds). It can be reproduced by this script:
> > 
> > export MALLOC_PERTURB_=11
> > qemu-img create -f qcow2 -o compat=1.1 test.qcow2 1M
> > time qemu-system-x86_64 -nographic -hda $TEST_IMG -serial none -monitor 
> > stdio <<EOF
> > savevm test
> > quit
> > EOF
> > 
> > This used to take about 0.6s for me, after this patch it's around 10s.
> 
> The solution could be to make bdrv_load_vmstate take an iov/iovcnt pair.

Ah, so you're saying that instead of linearising the buffer it breaks up
the requests in tiny pieces?

Implementing vectored bdrv_load/save_vmstate should be easy in theory.

> Alternatively, you can try the attached patch.  I haven't yet tested it
> though, and won't be able to do so today.

Attempted to write to buffer while read buffer is not empty

Program received signal SIGABRT, Aborted.

Kevin