x86/UV: Lower UV rtc clocksource rating
Lower the rating of the UV rtc clocksource to just below that of
the tsc, to improve performance.
Reading the tsc clocksource has lower latency than reading the
rtc, so favor it in situations where it is synchronized and
stable. When the tsc is unsynchronized, the rtc needs to be the
chosen clocksource.
Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Jack Steiner <steiner@sgi.com>
Link: http://lkml.kernel.org/r/20120217141641.GA28063@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c
index 9f29a01..5032e0d 100644
--- a/arch/x86/platform/uv/uv_time.c
+++ b/arch/x86/platform/uv/uv_time.c
@@ -37,7 +37,7 @@
static struct clocksource clocksource_uv = {
.name = RTC_NAME,
- .rating = 400,
+ .rating = 299,
.read = uv_read_rtc,
.mask = (cycle_t)UVH_RTC_REAL_TIME_CLOCK_MASK,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
@@ -379,10 +379,6 @@
if (!is_uv_system())
return -ENODEV;
- /* If single blade, prefer tsc */
- if (uv_num_possible_blades() == 1)
- clocksource_uv.rating = 250;
-
rc = clocksource_register_hz(&clocksource_uv, sn_rtc_cycles_per_second);
if (rc)
printk(KERN_INFO "UV RTC clocksource failed rc %d\n", rc);
