On Wed, Aug 04, 2010 at 07:17:30PM -0400, Kevin O'Connor wrote: > On Wed, Aug 04, 2010 at 06:25:52PM +0300, Gleb Natapov wrote: > > On Wed, Aug 04, 2010 at 09:57:17AM -0500, Anthony Liguori wrote: > > > There are better ways like using string I/O and optimizing the PIO > > > path in the kernel. That should cut down the 1s slow down with a > > > 100MB initrd by a bit. But honestly, shaving a couple hundred ms > > > further off the initrd load is just not worth it using the current > > > model. > > > > > The slow down is not 1s any more. String PIO emulation had many bugs > > that were fixed in 2.6.35. I verified how much time it took to load 100M > > via fw_cfg interface on older kernel and on 2.6.35. On older kernels on > > my machine it took ~2-3 second on 2.6.35 it took 26s. Some optimizations > > that was already committed make it 20s. I have some code prototype that > > makes it 11s. I don't see how we can get below that, surely not back to > > ~2-3sec. > > I guess this slowness is primarily for kvm. I just ran some tests on > the latest qemu (with TCG). I pulled in a 400Meg file over fw_cfg > using the SeaBIOS interface - it takes 9.8 seconds (pretty > consistently). Oddly, if I change SeaBIOS to use insb (string pio) it > takes 11.5 seconds (again, pretty consistently). These times were > measured on the host - they don't include the extra time it takes qemu > to start up (during which it reads the file into its memory). > Yes only KVM is affected, nothing has changed in qemu itself. -- Gleb. -- 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
