From: Felipe Franciosi Date: Fri, 19 May 2017 21:29:50 +0000 (+0100) Subject: cpus: reset throttle_thread_scheduled after sleep X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=90bb0c04214545beb75044a2742f711335103269;p=qemu.git cpus: reset throttle_thread_scheduled after sleep Currently, the throttle_thread_scheduled flag is reset back to 0 before sleeping (as part of the throttling logic). Given that throttle_timer (well, any timer) may tick with a slight delay, it so happens that under heavy throttling (ie. close or on CPU_THROTTLE_PCT_MAX) the tick may schedule a further cpu_throttle_thread() work item after the flag reset, but before the previous sleep completed. This results on the vCPU thread sleeping continuously for potentially several seconds in a row. The chances of that happening can be drastically minimised by resetting the flag after the sleep. Signed-off-by: Felipe Franciosi Signed-off-by: Malcolm Crossley Message-Id: <1495229390-18909-1-git-send-email-felipe@nutanix.com> Acked-by: Jason J. Herne Signed-off-by: Paolo Bonzini --- diff --git a/cpus.c b/cpus.c index 6398439946..14bb8d552e 100644 --- a/cpus.c +++ b/cpus.c @@ -677,9 +677,9 @@ static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque) sleeptime_ns = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS); qemu_mutex_unlock_iothread(); - atomic_set(&cpu->throttle_thread_scheduled, 0); g_usleep(sleeptime_ns / 1000); /* Convert ns to us for usleep call */ qemu_mutex_lock_iothread(); + atomic_set(&cpu->throttle_thread_scheduled, 0); } static void cpu_throttle_timer_tick(void *opaque)