Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 15 Jul 2015 11:44:06 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH v2 5/6] locking/pvqspinlock: Opportunistically defer kicking to unlock time |
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On 07/15/2015 07:43 AM, Waiman Long wrote: > Performing CPU kicking at lock time can be a bit faster if there > is no kick-ahead. On the other hand, deferring it to unlock time is > preferrable when kick-ahead can be performed or when the VM guest is > having too few vCPUs that a vCPU may be kicked twice before getting > the lock. This patch implements the deferring kicking when either > one of the above 2 conditions is true. > > Linux kernel builds were run in KVM guest on an 8-socket, 4 > cores/socket Westmere-EX system and a 4-socket, 8 cores/socket > Haswell-EX system. Both systems are configured to have 32 physical > CPUs. The kernel build times before and after the patch were: > > Westmere Haswell > Patch 32 vCPUs 48 vCPUs 32 vCPUs 48 vCPUs > ----- -------- -------- -------- -------- > Before patch 3m27.4s 10m32.0s 2m00.8s 14m52.5s > After patch 3m01.3s 9m50.9s 2m00.5s 13m28.1s > > On Westmere, both 32/48 vCPUs case showed some sizeable increase > in performance. For Haswell, there was some improvement in the > overcommitted (48 vCPUs) case. > > Signed-off-by: Waiman Long <Waiman.Long@hp.com> > ---
Hi Waiman,
For virtual guests, from my experiments, lock waiter preemption was the main concern especially with fair locks. I find that these set of patches are in right direction to address them.
Thanks for the patches.
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