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author | Keir Fraser <keir.fraser@citrix.com> | 2008-07-28 11:33:28 +0100 |
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committer | Keir Fraser <keir.fraser@citrix.com> | 2008-07-28 11:33:28 +0100 |
commit | 42bcbe769e71ec55daf48277c91119cbd3d53096 (patch) | |
tree | f124d8fea3663dbac5da0dcffc8a636650075320 | |
parent | 5589b0008c2bb9992ed6b76ebf7123bd73d75b56 (diff) | |
download | xen-42bcbe769e71ec55daf48277c91119cbd3d53096.tar.gz xen-42bcbe769e71ec55daf48277c91119cbd3d53096.tar.bz2 xen-42bcbe769e71ec55daf48277c91119cbd3d53096.zip |
x86: Roughly synchronise calls to local_time_calibration().
This results in reduced skew; both max and average skew are reduced by
between a factor of 2 and 3. Note that timers still fire at slightly
different times because the next "round epoch" is still relative to
local stime which still has some inter-processor skew.
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
-rw-r--r-- | xen/arch/x86/time.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index 72f1c4a6c1..570a630884 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -35,7 +35,8 @@ static char opt_clocksource[10]; string_param("clocksource", opt_clocksource); -#define EPOCH MILLISECS(1000) +#define EPOCH (1ULL << 30) /* one second, rounded up to a power of two */ +#define NEXT_EPOCH(now) (((now) + (EPOCH+(EPOCH/2))) & ~(EPOCH-1)) unsigned long cpu_khz; /* CPU clock frequency in kHz. */ DEFINE_SPINLOCK(rtc_lock); @@ -1021,7 +1022,7 @@ static void local_time_calibration(void *unused) update_vcpu_system_time(current); out: - set_timer(&t->calibration_timer, NOW() + EPOCH); + set_timer(&t->calibration_timer, NEXT_EPOCH(curr_local_stime)); if ( smp_processor_id() == 0 ) platform_time_calibration(); @@ -1050,7 +1051,7 @@ void init_percpu_time(void) out: init_timer(&t->calibration_timer, local_time_calibration, NULL, smp_processor_id()); - set_timer(&t->calibration_timer, NOW() + EPOCH); + set_timer(&t->calibration_timer, NEXT_EPOCH(NOW())); } /* Late init function (after all CPUs are booted). */ |