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

[Kevin Wolf]

Am 22.03.2013 um 15:48 hat Orit Wasserman geschrieben:
> This will remove an unneeded copy of guest memory pages.
> For the page header and device state we still copy the data to the
> static buffer the other option is to allocate the memory on demand
> which is more expensive.
> 
> Signed-off-by: Orit Wasserman <address@hidden>

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.

Kevin