[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Scalable Event Channel ABI design (draft A)
On 04/02/2013 21:07, "Wei Liu" <wei.liu2@xxxxxxxxxx> wrote: >> Concurrent access by Xen to the event queue must be protected by a >> per-event queue spin lock. >> > > I presume "E[n]" in the pseudo code is "E[p]"? > > Is this spin lock really a good idea? How many threads / cpus will spin > on this lock? As [0] shows, contention on spin lock incurs heavy > performance penalty. > > [0] https://lwn.net/Articles/530458/ Given that the critical region is small, the extra cache line contention for the spinlock is probably not a big deal. Even in the current event-channel design, we would get cache ping-pong on the event-channel bitmaps. Consider 10k interrupts to a CPU would be a heavy amount. That's one every 100us. The event-channel delivery code described probably runs in less than 1us, even if memory accesses are horrible cache misses. The really highly contended case shouldn't happen. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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