Date: Mon, 22 Aug 2011 03:10:29 +0000 (UTC) From: Mike Silbersack <silby@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r225069 - head/sys/x86/x86 Message-ID: <201108220310.p7M3ATr2030990@svn.freebsd.org>
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Author: silby Date: Mon Aug 22 03:10:29 2011 New Revision: 225069 URL: http://svn.freebsd.org/changeset/base/225069 Log: Disable TSC usage inside SMP VM environments. On my VMware ESXi 4.1 environment with a core i5-2500K, operation in this mode causes timeouts from the mpt driver. Switching to the ACPI-fast timer resolves this issue. Switching the VM back to single CPU mode also works, which is why I have not disabled the TSC in that mode. I did not test with KVM or other VM environments, but I am being cautious and assuming that the TSC is not reliable in SMP mode there as well. Reviewed by: kib Approved by: re (kib) MFC after: Not applicable, the timecounter code is new for 9.x Modified: head/sys/x86/x86/tsc.c Modified: head/sys/x86/x86/tsc.c ============================================================================== --- head/sys/x86/x86/tsc.c Sun Aug 21 22:09:30 2011 (r225068) +++ head/sys/x86/x86/tsc.c Mon Aug 22 03:10:29 2011 (r225069) @@ -464,11 +464,16 @@ init_TSC_tc(void) * synchronized. If the user is sure that the system has synchronized * TSCs, set kern.timecounter.smp_tsc tunable to a non-zero value. * We also limit the frequency even lower to avoid "temporal anomalies" - * as much as possible. + * as much as possible. The TSC seems unreliable in virtualized SMP + * environments, so it is set to a negative quality in those cases. */ if (smp_cpus > 1) { - tsc_timecounter.tc_quality = test_smp_tsc(); - max_freq >>= 8; + if (vm_guest != 0) { + tsc_timecounter.tc_quality = -100; + } else { + tsc_timecounter.tc_quality = test_smp_tsc(); + max_freq >>= 8; + } } else #endif if (tsc_is_invariant)
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