Date: Thu, 07 Apr 2011 20:12:38 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: FreeBSD current <freebsd-current@FreeBSD.org> Subject: prefer tsc timecounter when it's good Message-ID: <4D9DF086.9020906@FreeBSD.org>
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Guys,
what do you think about the following change?
The idea is mark TSC as the best timecounter when it's invariant and synchronized
between cores.
Unfortunately I don't have code to auto-detect the synchronization and keep
relying on the corresponding tunable. I thought about auto-setting it for
single-package configurations, but even that information is currently not trivial
to get out of our mp (i386/amd64) machdep code.
--- a/sys/x86/x86/tsc.c
+++ b/sys/x86/x86/tsc.c
@@ -169,6 +169,9 @@ init_TSC_tc(void)
printf("TSC timecounter disabled: APM enabled.\n");
}
+ if (tsc_is_invariant)
+ tsc_timecounter.tc_quality = 1200;
+
#ifdef SMP
/*
* We can not use the TSC in SMP mode unless the TSCs on all CPUs
--
Andriy Gapon
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