using smart idle poll to reduce the useless poll when system is idle. Signed-off-by: Yang Zhang <yang.zhang...@gmail.com> Signed-off-by: Quan Xu <quan....@gmail.com> Cc: Paolo Bonzini <pbonz...@redhat.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@redhat.com> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: x...@kernel.org Cc: k...@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- arch/x86/kernel/kvm.c | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 7d84a02..ffc8307 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -373,12 +373,53 @@ static void kvm_idle_poll(void) } while (ktime_before(cur, stop)); } +static unsigned int grow_poll_ns(unsigned int old, unsigned int grow, + unsigned int max) +{ + unsigned int val; + + /* set base poll time to 10000ns */ + if (old == 0 && grow) + return 10000; + + val = old * grow; + if (val > max) + val = max; + + return val; +} + +static unsigned int shrink_poll_ns(unsigned int old, unsigned int shrink) +{ + if (shrink == 0) + return 0; + + return old / shrink; +} + +static int kvm_idle_update_poll_duration(unsigned long idle_duration) +{ + unsigned long poll_duration = this_cpu_read(poll_duration_ns); + + if (poll_duration && idle_duration > poll_threshold_ns) + poll_duration = shrink_poll_ns(poll_duration, poll_shrink); + else if (poll_duration < poll_threshold_ns && + idle_duration < poll_threshold_ns) + poll_duration = grow_poll_ns(poll_duration, poll_grow, + poll_threshold_ns); + + this_cpu_write(poll_duration_ns, poll_duration); + + return 0; +} + static void kvm_guest_idle_init(void) { if (!kvm_para_available()) return; pv_idle_ops.poll = kvm_idle_poll; + pv_idle_ops.update = kvm_idle_update_poll_duration; } static void kvm_pv_disable_apf(void) -- 1.8.3.1