On Fri, Apr 04, 2014 at 01:58:15PM -0400, Konrad Rzeszutek Wilk wrote: > On Fri, Apr 04, 2014 at 01:13:17PM -0400, Waiman Long wrote: > > On 04/04/2014 12:55 PM, Konrad Rzeszutek Wilk wrote: > > >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. > > > > What I am saying is that when XEN and PV spinlock is compiled into > > the current upstream kernel, the PV spinlock jump label is turned on > > when booted on bare metal. In other words, the PV spinlock code is > > How does it turn it on? I see that the jump lables are only turned > on when the jump label is enable when it detects that it is running > under Xen or KVM. It won't turn it on under baremetal. Well, it seems that it does turn it on baremetal which is an stupid mistake. Sending a patch shortly. > > > active even when they are not needed and actually slow thing down in > > that situation. This is a problem and we need to find way to make > > sure that the PV spinlock code won't be activated on bare metal. > > Could you explain to me which piece of code enables the jump labels > on baremetal please? > > > > -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
