Messages in this thread | | | Date | Mon, 13 Jul 2015 15:52:20 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 2/7] locking/pvqspinlock: Allow vCPUs kick-ahead |
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On Sat, Jul 11, 2015 at 04:36:53PM -0400, Waiman Long wrote: > Frequent CPU halting (vmexit) and CPU kicking (vmenter) lengthens > critical section and block forward progress. This patch implements > a kick-ahead mechanism where the unlocker will kick the queue head > vCPUs as well as up to two additional vCPUs next to the queue head if > they were halted. The kickings are done after exiting the critical > section to improve parallelism. > > The amount of kick-ahead allowed depends on the number of vCPUs in > the VM guest. This change should improve overall system performance > in a busy overcommitted guest.
-ENONUMBERS... also highly workload sensitive, if the lock hold time is just above our spin time you're wasting gobs of runtime.
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