Messages in this thread Patch in this message | | | Date | Wed, 24 Oct 2012 03:34:23 -0700 | From | tip-bot for Vince Weaver <> | Subject | [tip:perf/urgent] perf/x86: Make Intel KNC use full 40-bit width of counters |
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Commit-ID: ae5ba47a990a18c869d66916fd72fb334c45cf91 Gitweb: http://git.kernel.org/tip/ae5ba47a990a18c869d66916fd72fb334c45cf91 Author: Vince Weaver <vincent.weaver@maine.edu> AuthorDate: Wed, 17 Oct 2012 13:03:21 -0400 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 24 Oct 2012 12:00:48 +0200
perf/x86: Make Intel KNC use full 40-bit width of counters
Early versions of Intel KNC chips have a bug where bits above 32 were not properly set. We worked around this by only using the bottom 32 bits (out of 40 that should be available).
It turns out this workaround breaks overflow handling.
The buggy silicon will in theory never be used in production systems, so remove this workaround so we get proper overflow support.
Signed-off-by: Vince Weaver <vincent.weaver@maine.edu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Cc: eranian@gmail.com Cc: Meadows Lawrence F <lawrence.f.meadows@intel.com> Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1210171302140.23243@vincent-weaver-1.um.maine.edu Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/kernel/cpu/perf_event_knc.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_knc.c b/arch/x86/kernel/cpu/perf_event_knc.c index 7c46bfd..73bcfbd 100644 --- a/arch/x86/kernel/cpu/perf_event_knc.c +++ b/arch/x86/kernel/cpu/perf_event_knc.c @@ -226,12 +226,11 @@ static __initconst struct x86_pmu knc_pmu = { .event_map = knc_pmu_event_map, .max_events = ARRAY_SIZE(knc_perfmon_event_map), .apic = 1, - .max_period = (1ULL << 31) - 1, + .max_period = (1ULL << 39) - 1, .version = 0, .num_counters = 2, - /* in theory 40 bits, early silicon is buggy though */ - .cntval_bits = 32, - .cntval_mask = (1ULL << 32) - 1, + .cntval_bits = 40, + .cntval_mask = (1ULL << 40) - 1, .get_event_constraints = x86_get_event_constraints, .event_constraints = knc_event_constraints, .format_attrs = intel_knc_formats_attr,
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