On Sun, Aug 22, 2010 at 10:31:55PM +0300, Avi Kivity wrote: > On 08/22/2010 10:02 PM, Richard W.M. Jones wrote: > >>Interesting, I'd have guessed that encryption will dominate the cpu > >>cost, and that compression would be a win since there's less to > >>encrypt and transmit. > >Maybe my explanation is wrong too. virt-p2v was definitely much > >slower when we added the '-C' option. However read on. > > > >I just ran a test again on my local LAN. This is between two > >approximately equal Fedora machines, over a moderate quality consumer > >gigabit ethernet switch. The command approximates what virt-p2v does: > >sending 1MB blocks from local /dev device, and at the target end using > >cat to write to a file. > > > >$ time sh -c 'dd bs=1M if=/dev/vg_trick/Windows7x64 | ssh amd "cat> > >/tmp/copy1"' > >16384+0 records in > >16384+0 records out > >17179869184 bytes (17 GB) copied, 1473.26 s, 11.7 MB/s > > > >real 24m33.269s > >user 4m16.944s > >sys 4m43.181s > > 11.7 MB/s = 93.6 Mb/s. Not the cpu is not loaded. Are you sure > you're using 1GbE here?
You're absolutely right -- I forget that it's a fast ethernet switch :-) > >$ time sh -c 'dd bs=1M if=/dev/vg_trick/Windows7x64 | ssh -C amd "cat> > >/tmp/copy2"' > >16384+0 records in > >16384+0 records out > >17179869184 bytes (17 GB) copied, 1412.7 s, 12.2 MB/s > > > >real 23m32.736s > >user 17m52.739s > >sys 5m0.884s > > > > Suddenly you're cpu bound. So it looks like compression is really > expensive for some reason. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones New in Fedora 11: Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 70 libraries supprt'd http://fedoraproject.org/wiki/MinGW http://www.annexia.org/fedora_mingw _______________________________________________ virt mailing list [email protected] https://admin.fedoraproject.org/mailman/listinfo/virt
