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? > $ 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. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. _______________________________________________ virt mailing list [email protected] https://admin.fedoraproject.org/mailman/listinfo/virt
