On 16/06/15 04:04, Mario Smarduch wrote: > On 06/15/2015 11:20 AM, Marc Zyngier wrote: >> On 15/06/15 19:04, Mario Smarduch wrote: >>> On 06/15/2015 03:00 AM, Marc Zyngier wrote: >>>> Hi Mario, >>>> > [ ... ] >>>> >>>> On 13/06/15 23:20, Mario Smarduch wrote: >>>>> Currently VFP/SIMD registers are always saved and restored >>>>> on Guest entry and exit. >>>>> >>>>> This patch only saves and restores VFP/SIMD registers on >>>>> Guest access. To do this cptr_el2 VFP/SIMD trap is set >>>>> on Guest entry and later checked on exit. This follows >>>>> the ARMv7 VFPv3 implementation. Running an informal test >>>>> there are high number of exits that don't access VFP/SIMD >>>>> registers. >>>> >>>> It would be good to add some numbers here. How often do we exit without >>>> having touched the FPSIMD regs? For which workload? >>> >>> Lmbench is what I typically use, with ssh server, i.e., cause page >>> faults and interrupts - usually registers are not touched. >>> I'll run the tests again and define usually. >>> >>> Any other loads you had in mind? >> >> Not really (apart from running hackbench, of course...;-). I'd just like >> to see the numbers in the commit message, so that we can document the >> improvement (and maybe track regressions). > > Hi Marc, > some ballpark numbers. > > hackbench about 30% of the time optimized path is taken > (for 10*40 test). > > Lmbench3 upwards of 50% for context switching, memory bw, > pipe, proc creation, sys call. There are lot more tests > but I limited to these tests. In addition other processes > are running in background NTP, SSH, ... doing their own > thing. > > I added a tmp counter to kvm_vcpu_arch to count vfpsimd > events. That looks good. Please include these numbers in the commit message for v2 of that patch. Thanks, M. -- Jazz is not dead. It just smells funny... -- 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
