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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