Hello, I am just catching up on this email thread...
Perhaps one of you may be able to help answer this query.. preferably along with some data. [BTW, I do understand the basic intent behind PLE in a typical [sweet spot] use case where there is over subscription etc. and the need to optimize the PLE handler in the host etc. ] In a use case where the host has fewer but much larger guests (say 40VCPUs and higher) and there is no over subscription (i.e. # of vcpus across guests <= physical cpus in the host and perhaps each guest has their vcpu's pinned to specific physical cpus for other reasons), I would like to understand if/how the PLE really helps ? For these use cases would it be ok to turn PLE off (ple_gap=0) since is no real need to take an exit and find some other VCPU to yield to ? Thanks Vinod -----Original Message----- From: Raghavendra K T [mailto:raghavendra...@linux.vnet.ibm.com] Sent: Thursday, June 28, 2012 9:22 AM To: Andrew Jones Cc: Rik van Riel; Marcelo Tosatti; Srikar; Srivatsa Vaddagiri; Peter Zijlstra; Nikunj A. Dadhania; KVM; LKML; Gleb Natapov; Vinod, Chegu; Jeremy Fitzhardinge; Avi Kivity; Ingo Molnar Subject: Re: [PATCH] kvm: handle last_boosted_vcpu = 0 case On 06/28/2012 09:30 PM, Andrew Jones wrote: > > > ----- Original Message ----- >> In summary, current PV has huge benefit on non-PLE machine. >> >> On PLE machine, the results become very sensitive to load, type of >> workload and SPIN_THRESHOLD. Also PLE interference has significant >> effect on them. But still it has slight edge over non PV. >> > > Hi Raghu, > > sorry for my slow response. I'm on vacation right now (until the 9th > of July) and I have limited access to mail. Ok. Happy Vacation :) Also, thanks for > continuing the benchmarking. Question, when you compare PLE vs. > non-PLE, are you using different machines (one with and one without), > or are you disabling its use by loading the kvm module with the > ple_gap=0 modparam as I did? Yes, I am doing the same when I say with PLE disabled and comparing the benchmarks (i.e loading kvm module with ple_gap=0). But older non-PLE results were on a different machine altogether. (I had limited access to PLE machine).
