On Wed, 2009-05-13 at 08:15 -0600, Alex Williamson wrote: > On Wed, 2009-05-13 at 16:55 +0300, Michael S. Tsirkin wrote: > > On Wed, May 13, 2009 at 07:11:16AM -0600, Alex Williamson wrote: > > > On Wed, 2009-05-13 at 16:00 +0300, Avi Kivity wrote: > > > > Alex Williamson wrote: > > > > >> > > > > >> When you say "multiple times", it is several, or a lot more? > > > > >> > > > > >> Maybe it is NAPI? > > > > >> > > > > > > > > > > The system would run out of the ~1000 available GSIs in a minute or > > > > > two > > > > > with just an e1000e available to the guest. So that's something on > > > > > the > > > > > order of 10/s. This also causes a printk in the host ever time the > > > > > interrupt in enabled, which can't help performance and gets pretty > > > > > annoying for syslog. I was guessing some kind of interrupt > > > > > mitigation, > > > > > such as NAPI, but a qlogic FC card seems to do it too (seemingly at a > > > > > slower rate). > > > > > > > > > > > > > I see. And what is the path by which it is disabled? The mask bit in > > > > the MSI entry? > > > > > > Yes, I believe the only path is via a write to the MSI capability in the > > > PCI config space. > > > > > > Alex > > > > Very surprising: I haven't seen any driver disable MSI expect on device > > destructor path. Is this a linux guest? > > Yes, Debian 2.6.26 kernel. I'll check it it behaves the same on newer > upstream kernels and try to figure out why it's doing it.
Updating the guest to 2.6.29 seems to fix the interrupt toggling. So it's either something in older kernels or something debian introduced, but that seems unlikely. Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
