On Wed, Jun 02, 2010 at 05:51:14AM +0300, Avi Kivity wrote: > On 06/01/2010 08:27 PM, Andi Kleen wrote: >> On Tue, Jun 01, 2010 at 07:52:28PM +0300, Avi Kivity wrote: >> >>> We are running everything on NUMA (since all modern machines are now NUMA). >>> At what scale do the issues become observable? >>> >> On Intel platforms it's visible starting with 4 sockets. >> > > Can you recommend a benchmark that shows bad behaviour? I'll run it with Pretty much anything with high lock contention. > ticket spinlocks and Gleb's patch. I have a 4-way Nehalem-EX, presumably > the huge number of threads will magnify the problem even more there. Yes more threads cause more lock contention too. > Do you have any idea how we can tackle both problems? Apparently Xen has something, perhaps that can be leveraged (but I haven't looked at their solution in detail) Otherwise I would probably try to start with a adaptive spinlock that at some point calls into the HV (or updates shared memory?), like john cooper suggested. The tricky part here would be to find the thresholds and fit that state into paravirt ops and the standard spinlock_t. -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only. -- 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
