On 06/23/10 03:13, Zhang, Yanmin wrote: > On Tue, 2010-06-22 at 09:58 +0200, Jes Sorensen wrote: >> Exposing the counters read-only would save a lot of overhead for sure. >>>> Question is if it is safe to drop overflow support? >>> Not safe. One of PMU hardware design objectives is to use interrupt or NMI to notify >>> software when event counter overflows. Without overflow support, software need poll >>> the PMU registers looply. That is not good and consumes more cpu resources. >> >> Here is an idea, how about having the overflow NMI in the host trigger a >> flag that causes the PMU register read to trap and get special handling? >> That way you could propagate the overflow back down to the guest. > That doesn't resolve the issue that guest os software has to poll register. That is true, but it could set a flag through the para virt interface. Cheers, Jes -- 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
