On 05/19/2017 05:29 PM, Felipe Franciosi wrote:
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 <fel...@nutanix.com>
Signed-off-by: Malcolm Crossley <malc...@nutanix.com>
---
cpus.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/cpus.c b/cpus.c
index 516e5cb..f42eebd 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)
This seems to make sense to me.
Acked-by: Jason J. Herne <jjhe...@linux.vnet.ibm.com>
I'm CC'ing Juan, Amit and David as they are all active in the migration
area and may have
opinions on this. Juan and David were also reviewers for the original
series.
--
-- Jason J. Herne (jjhe...@linux.vnet.ibm.com)
