On Wed, Sep 2, 2015 at 12:29 AM, Wanpeng Li <wanpeng...@hotmail.com> wrote: > v5 -> v6: > * fix wait_ns and poll_ns
Thanks for bearing with me through all the reviews. I think it's on the verge of being done :). There are just few small things to fix. > > v4 -> v5: > * set base case 10us and max poll time 500us > * handle short/long halt, idea from David, many thanks David ;-) > > v3 -> v4: > * bring back grow vcpu->halt_poll_ns when interrupt arrives and shrinks > when idle VCPU is detected > > v2 -> v3: > * grow/shrink vcpu->halt_poll_ns by *halt_poll_ns_grow or > /halt_poll_ns_shrink > * drop the macros and hard coding the numbers in the param definitions > * update the comments "5-7 us" > * remove halt_poll_ns_max and use halt_poll_ns as the max halt_poll_ns time, > vcpu->halt_poll_ns start at zero > * drop the wrappers > * move the grow/shrink logic before "out:" w/ "if (waited)" > > v1 -> v2: > * change kvm_vcpu_block to read halt_poll_ns from the vcpu instead of > the module parameter > * use the shrink/grow matrix which is suggested by David > * set halt_poll_ns_max to 2ms > > There is a downside of always-poll since poll is still happened for idle > vCPUs which can waste cpu usage. This patchset add the ability to adjust > halt_poll_ns dynamically, to grow halt_poll_ns when shot halt is detected, > and to shrink halt_poll_ns when long halt is detected. > > There are two new kernel parameters for changing the halt_poll_ns: > halt_poll_ns_grow and halt_poll_ns_shrink. > > no-poll always-poll dynamic-poll > ----------------------------------------------------------------------- > Idle (nohz) vCPU %c0 0.15% 0.3% 0.2% > Idle (250HZ) vCPU %c0 1.1% 4.6%~14% 1.2% > TCP_RR latency 34us 27us 26.7us > > "Idle (X) vCPU %c0" is the percent of time the physical cpu spent in > c0 over 60 seconds (each vCPU is pinned to a pCPU). (nohz) means the > guest was tickless. (250HZ) means the guest was ticking at 250HZ. > > The big win is with ticking operating systems. Running the linux guest > with nohz=off (and HZ=250), we save 3.4%~12.8% CPUs/second and get close > to no-polling overhead levels by using the dynamic-poll. The savings > should be even higher for higher frequency ticks. > > > Wanpeng Li (3): > KVM: make halt_poll_ns per-vCPU > KVM: dynamic halt_poll_ns adjustment > KVM: trace kvm_halt_poll_ns grow/shrink > > include/linux/kvm_host.h | 1 + > include/trace/events/kvm.h | 30 ++++++++++++++++++++ > virt/kvm/kvm_main.c | 70 > ++++++++++++++++++++++++++++++++++++++++++---- > 3 files changed, 96 insertions(+), 5 deletions(-) > > -- > 1.9.1 > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
