On Thu, Apr 03, 2014 at 10:57:18PM -0400, Waiman Long wrote: > On 04/03/2014 01:23 PM, Konrad Rzeszutek Wilk wrote: > >On Wed, Apr 02, 2014 at 10:10:17PM -0400, Waiman Long wrote: > >>On 04/02/2014 04:35 PM, Waiman Long wrote: > >>>On 04/02/2014 10:32 AM, Konrad Rzeszutek Wilk wrote: > >>>>On Wed, Apr 02, 2014 at 09:27:29AM -0400, Waiman Long wrote: > >>>>>N.B. Sorry for the duplicate. This patch series were resent as the > >>>>> original one was rejected by the vger.kernel.org list server > >>>>> due to long header. There is no change in content. > >>>>> > >>>>>v7->v8: > >>>>> - Remove one unneeded atomic operation from the slowpath, thus > >>>>> improving performance. > >>>>> - Simplify some of the codes and add more comments. > >>>>> - Test for X86_FEATURE_HYPERVISOR CPU feature bit to enable/disable > >>>>> unfair lock. > >>>>> - Reduce unfair lock slowpath lock stealing frequency depending > >>>>> on its distance from the queue head. > >>>>> - Add performance data for IvyBridge-EX CPU. > >>>>FYI, your v7 patch with 32 VCPUs (on a 32 cpu socket machine) on an > >>>>HVM guest under Xen after a while stops working. The workload > >>>>is doing 'make -j32' on the Linux kernel. > >>>> > >>>>Completely unresponsive. Thoughts? > >>>> > >>>Thank for reporting that. I haven't done that much testing on Xen. > >>>My focus was in KVM. I will perform more test on Xen to see if I > >>>can reproduce the problem. > >>> > >>BTW, does the halting and sending IPI mechanism work in HVM? I saw > >Yes. > >>that in RHEL7, PV spinlock was explicitly disabled when in HVM mode. > >>However, this piece of code isn't in upstream code. So I wonder if > >>there is problem with that. > >The PV ticketlock fixed it for HVM. It was disabled before because > >the PV guests were using bytelocks while the HVM were using ticketlocks > >and you couldnt' swap in PV bytelocks for ticketlocks during startup. > > The RHEL7 code has used PV ticketlock already. RHEL7 uses a single > kernel for all configurations. So PV ticketlock as well as Xen and > KVM support was compiled in. I think booting the kernel on bare > metal will cause the Xen code to work in HVM mode thus activating > the PV spinlock code which has a negative impact on performance. Huh? -EPARSE > That may be why it was disabled so that the bare metal performance > will not be impacted. I am not following you. > > BTW, could you send me more information about the configuration of > the machine, like the .config file that you used? Marcos, could you please send that information to Peter. Thanks! > > -Longman -- 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
