On Mon, Jun 13, 2011 at 07:02:27PM +0530, Krishna Kumar2 wrote: > "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote on 06/07/2011 09:38:30 PM: > > > > This is on top of the patches applied by Rusty. > > > > > > Warning: untested. Posting now to give people chance to > > > comment on the API. > > > > OK, this seems to have survived some testing so far, > > after I dropped patch 4 and fixed build for patch 3 > > (build fixup patch sent in reply to the original). > > > > I'll be mostly offline until Sunday, would appreciate > > testing reports. > > Hi Michael, > > I ran the latest patches with 1K I/O (guest->local host) and > the results are (60 sec run for each test case): > > ______________________________ > #sessions BW% SD% > ______________________________ > 1 -25.6 47.0 > 2 -29.3 22.9 > 4 .8 1.6 > 8 1.6 0 > 16 -1.6 4.1 > 32 -5.3 2.1 > 48 11.3 -7.8 > 64 -2.8 .7 > 96 -6.2 .6 > 128 -10.6 12.7 > ______________________________ > BW: -4.8 SD: 5.4 > > I tested it again to see if the regression is fleeting (since > the numbers vary quite a bit for 1K I/O even between guest-> > local host), but: > > ______________________________ > #sessions BW% SD% > ______________________________ > 1 14.0 -17.3 > 2 19.9 -11.1 > 4 7.9 -15.3 > 8 9.6 -13.1 > 16 1.2 -7.3 > 32 -.6 -13.5 > 48 -28.7 10.0 > 64 -5.7 -.7 > 96 -9.4 -8.1 > 128 -9.4 .7 > ______________________________ > BW: -3.7 SD: -2.0 > > > With 16K, there was an improvement in SD, but > higher sessions seem to slightly degrade BW/SD: > > ______________________________ > #sessions BW% SD% > ______________________________ > 1 30.9 -25.0 > 2 16.5 -19.4 > 4 -1.3 7.9 > 8 1.4 6.2 > 16 3.9 -5.4 > 32 0 4.3 > 48 -.5 .1 > 64 32.1 -1.5 > 96 -2.1 23.2 > 128 -7.4 3.8 > ______________________________ > BW: 5.0 SD: 7.5 > > > Thanks, > > - KK I think I see one scenario where we do extra work: when TX ring overflows, the first attempt to add buf will fail, so the work to format the s/g list is then wasted. So it might make sense to free up buffers up to capacity first thing after all, which will still do nothing typically, add buf afterwards. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
