Am 03.11.2010 10:10, Michael S. Tsirkin wrote: > On Wed, Nov 03, 2010 at 09:56:24AM +0100, Jan Kiszka wrote: >>> Hmm, this does an extra config read on each interrupt (another one is in >>> pci_2_3_irq_unmask). These reads are pretty expensive... I do realize >>> locking becomes ugly, though. Maybe my idea to avoid set level to 0 >>> was silly? Thoughts? >> >> Well, reading twice is the price to pay here, putting kvm_set_irq under >> spin_lock_irq again is a no-go. From that POV, the previous version was >> probably the cheapest: no extra efforts in the common case, but still >> avoiding reassertion via the host IRQ handler whenever possible. >> >> Jan >> > > Sigh. I guess so. Any chance of a benchmark to let us figure this out? > Will see what I can do. 2.6.37 claims to have improved IRQ load accounting, maybe that helps to measure something useful. Jan
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