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author | cperciva <cperciva@FreeBSD.org> | 2010-12-11 22:33:33 +0000 |
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committer | cperciva <cperciva@FreeBSD.org> | 2010-12-11 22:33:33 +0000 |
commit | b173b18025943e9b8fb30f95e8c8ad3161b21b0d (patch) | |
tree | e749edcd762588ceeb55969be6c576f03756fe2e /sys/i386/xen | |
parent | 9f0c1183494ccb03e81314e3abc2e1dd7687f6bb (diff) | |
download | FreeBSD-src-b173b18025943e9b8fb30f95e8c8ad3161b21b0d.zip FreeBSD-src-b173b18025943e9b8fb30f95e8c8ad3161b21b0d.tar.gz |
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.
Diffstat (limited to 'sys/i386/xen')
-rw-r--r-- | sys/i386/xen/clock.c | 5 |
1 files changed, 3 insertions, 2 deletions
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); } |