diff options
| -rw-r--r-- | virt/kvm/kvm_main.c | 53 |
1 files changed, 51 insertions, 2 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index c06e57cd1269..8ab49cfc024e 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -66,9 +66,18 @@ MODULE_AUTHOR("Qumranet"); MODULE_LICENSE("GPL"); -static unsigned int halt_poll_ns; +/* halt polling only reduces halt latency by 5-7 us, 500us is enough */ +static unsigned int halt_poll_ns = 500000; module_param(halt_poll_ns, uint, S_IRUGO | S_IWUSR); +/* Default doubles per-vcpu halt_poll_ns. */ +static unsigned int halt_poll_ns_grow = 2; +module_param(halt_poll_ns_grow, int, S_IRUGO); + +/* Default resets per-vcpu halt_poll_ns . */ +static unsigned int halt_poll_ns_shrink; +module_param(halt_poll_ns_shrink, int, S_IRUGO); + /* * Ordering of locks: * @@ -1907,6 +1916,31 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn) } EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty); +static void grow_halt_poll_ns(struct kvm_vcpu *vcpu) +{ + int val = vcpu->halt_poll_ns; + + /* 10us base */ + if (val == 0 && halt_poll_ns_grow) + val = 10000; + else + val *= halt_poll_ns_grow; + + vcpu->halt_poll_ns = val; +} + +static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu) +{ + int val = vcpu->halt_poll_ns; + + if (halt_poll_ns_shrink == 0) + val = 0; + else + val /= halt_poll_ns_shrink; + + vcpu->halt_poll_ns = val; +} + static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu) { if (kvm_arch_vcpu_runnable(vcpu)) { @@ -1929,6 +1963,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) ktime_t start, cur; DEFINE_WAIT(wait); bool waited = false; + u64 block_ns; start = cur = ktime_get(); if (vcpu->halt_poll_ns) { @@ -1961,7 +1996,21 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) cur = ktime_get(); out: - trace_kvm_vcpu_wakeup(ktime_to_ns(cur) - ktime_to_ns(start), waited); + block_ns = ktime_to_ns(cur) - ktime_to_ns(start); + + if (halt_poll_ns) { + if (block_ns <= vcpu->halt_poll_ns) + ; + /* we had a long block, shrink polling */ + else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) + shrink_halt_poll_ns(vcpu); + /* we had a short halt and our poll time is too small */ + else if (vcpu->halt_poll_ns < halt_poll_ns && + block_ns < halt_poll_ns) + grow_halt_poll_ns(vcpu); + } + + trace_kvm_vcpu_wakeup(block_ns, waited); } EXPORT_SYMBOL_GPL(kvm_vcpu_block); |