Switch longer OSWaitus to descheduling the thread
Long spins are a waste of CPU. Also when spinning use some yield
instructions, since that might be slightly more efficient.
Change-Id: Ic7b2f33abd7951df535c12303a1b11033b4c4247
diff --git a/services/server/env/fuchsia/osfunc.cc b/services/server/env/fuchsia/osfunc.cc
index c91b77c..bfd3c71 100644
--- a/services/server/env/fuchsia/osfunc.cc
+++ b/services/server/env/fuchsia/osfunc.cc
@@ -409,9 +409,24 @@
void
OSWaitus(IMG_UINT32 ui32Timeus)
{
- uint64_t start = OSClockus64();
- while (OSClockus64() - start < ui32Timeus)
- ;
+ // We don't have to worry about interrupt contexts or anything like that, so it's reasonable
+ // to sleep if the desired delay is long enough. 50 microseconds is a reasonable guess about
+ // how long is enough time for another thread to do some useful work after being scheduled
+ // in.
+ if (ui32Timeus > 50)
+ {
+ zx_nanosleep(zx_deadline_after(ZX_USEC(ui32Timeus)));
+ }
+ else
+ {
+ uint64_t start = OSClockus64();
+ while (OSClockus64() - start < ui32Timeus)
+ {
+#if defined(__aarch64__)
+ __asm__ __volatile__("yield");
+#endif
+ }
+ }
}
void
