Anthony Liguori wrote: > On 05/18/2010 11:26 AM, Alexander Graf wrote: >> Jes Sorensen wrote: >> >>> 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! >>> >>> >> It looks like a fairly small change with a huge win. Sounds like a >> perfect candidate for 0.12.5 to me. >> > > I'd prefer to stick to bug fixes for stable releases. Performance > improvements are a good motivation for people to upgrade to 0.13 :-)
In general I agree, but this one looks like a really simple one. Alex
