Date: Wed, 8 Jun 2011 19:38:31 +0000 (UTC) From: Jung-uk Kim <jkim@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/x86/x86 tsc.c Message-ID: <201106081938.p58Jcgr2039146@repoman.freebsd.org>
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jkim 2011-06-08 19:38:31 UTC
FreeBSD src repository
Modified files:
sys/x86/x86 tsc.c
Log:
SVN rev 222866 on 2011-06-08 19:38:31Z by jkim
Introduce low-resolution TSC timecounter "TSC-low". It replaces the normal
TSC timecounter if TSC frequency is higher than ~4.29 MHz (or 2^32-1 Hz) or
multiple CPUs are present. The "TSC-low" frequency is always lower than a
preset maximum value and derived from TSC frequency (by being halved until
it becomes lower than the maximum). Note the maximum value for SMP case is
significantly lower than UP case because we want to reduce (rare but known)
"temporal anomalies" caused by non-serialized RDTSC instruction. Normally,
it is still higher than "ACPI-fast" timecounter frequency (which was default
timecounter hardware for long time until r222222) to be useful.
Revision Changes Path
1.21 +38 -6 src/sys/x86/x86/tsc.c
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