From b173b18025943e9b8fb30f95e8c8ad3161b21b0d Mon Sep 17 00:00:00 2001 From: cperciva Date: Sat, 11 Dec 2010 22:33:33 +0000 Subject: Reduce the Xen timecounter from 1GHz to 2^-9 GHz, thereby increasing the timecounter period from 2^32 ns (~4.3s) to 2^41 ns (~36m39s). Some time sharing systems can skip clock interrupts for a few seconds when under load (e.g., if we've recently used more than our fair share of CPU and someone else wants a burst of CPU) and we were losing time in quanta of 2^32 ns due to timecounter wrapping. Increasing the timecounter period up to 2^41 ns is definitely overkill, but we still have microsecond timecounter precision, and anyone using paravirtualized hardware when they need submicrosecond timing is crazy. --- sys/i386/xen/clock.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'sys/i386/xen/clock.c') diff --git a/sys/i386/xen/clock.c b/sys/i386/xen/clock.c index 5efd66d..03f2517 100644 --- a/sys/i386/xen/clock.c +++ b/sys/i386/xen/clock.c @@ -523,7 +523,8 @@ startrtclock() set_cyc2ns_scale(cpu_khz/1000); tsc_freq = cpu_khz * 1000; - timer_freq = xen_timecounter.tc_frequency = 1000000000LL; + timer_freq = 1000000000LL; + xen_timecounter.tc_frequency = timer_freq >> 9; tc_init(&xen_timecounter); rdtscll(alarm); @@ -830,7 +831,7 @@ xen_get_timecount(struct timecounter *tc) clk = shadow->system_timestamp + get_nsec_offset(shadow); - return (uint32_t)(clk); + return (uint32_t)(clk >> 9); } -- cgit v1.1