On 05/14/10 23:52, Stefan Hajnoczi wrote: > The VirtIOBlockRequest structure is about 40 KB in size. This patch > avoids zeroing every request by only initializing fields that are read. > The other fields are either written to or may not be used at all. > > Oprofile shows about 10% of CPU samples in memset called by > virtio_blk_alloc_request(). The workload is > dd if=/dev/vda of=/dev/null iflag=direct bs=8k running concurrently 4 > times. This patch makes memset disappear to the bottom of the profile. > > Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
Great catch! I ran some benchmarks using a ramdisk passed to the guest as a virtio device and with this patch I saw improvements ranging from 5-20%. I believe the fluctuations are due to not being able to numa bind it due to limited memory. However a win all the way round! Acked-by: Jes Sorensen <jes.soren...@redhat.com> Jes
