Rik van Riel <riel <at> redhat.com> writes: > > On 04/11/2012 01:21 PM, Chegu Vinod wrote: > > > > Hello, > > > > While running an AIM7 (workfile.high_systime) in a single 40-way (or a single > > 60-way KVM guest) I noticed pretty bad performance when the guest was booted > > with 3.3.1 kernel when compared to the same guest booted with 2.6.32-220 > > (RHEL6.2) kernel. > > > For the 40-way Guest-RunA (2.6.32-220 kernel) performed nearly 9x better than > > the Guest-RunB (3.3.1 kernel). In the case of 60-way guest run the older guest > > kernel was nearly 12x better ! > > > Turned on function tracing and found that there appears to be more time being > > spent around the lock code in the 3.3.1 guest when compared to the 2.6.32- 220 > > guest. > > Looks like you may be running into the ticket spinlock > code. During the early RHEL 6 days, Gleb came up with a > patch to automatically disable ticket spinlocks when > running inside a KVM guest. > Thanks for the pointer. Perhaps that is the issue. I did look up that old discussion thread. > IIRC that patch got rejected upstream at the time, > with upstream developers preferring to wait for a > "better solution". > > If such a better solution is not on its way upstream > now (two years later), maybe we should just merge > Gleb's patch upstream for the time being? Also noticed a recent discussion thread (that originated from the Xen context) http://article.gmane.org/gmane.linux.kernel.virtualization/15078 Not yet sure if this recent discussion is also in some way related to the older one initiated by Gleb. Thanks Vinod -- 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
