diff options
| author | Robert Richter <robert.richter@amd.com> | 2009-04-29 12:47:01 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-04-29 14:51:02 +0200 |
| commit | 4295ee62660b13ddb87d41539f49b239e6e7d56f (patch) | |
| tree | bdd7c1b1c1b4c1c4b05d42d4837c6fbf8ad5e5f8 | |
| parent | 4138960a9251a265002b5cf07e671a49f8495381 (diff) | |
perf_counter, x86: rework pmc_amd_save_disable_all() and pmc_amd_restore_all()
MSR reads and writes are expensive. This patch adds checks to avoid
its usage where possible.
[ Impact: micro-optimization on AMD CPUs ]
Signed-off-by: Robert Richter <robert.richter@amd.com>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1241002046-8832-5-git-send-email-robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | arch/x86/kernel/cpu/perf_counter.c | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index d6d6529349d..75a090394b6 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -334,11 +334,13 @@ static u64 pmc_amd_save_disable_all(void) for (idx = 0; idx < nr_counters_generic; idx++) { u64 val; + if (!test_bit(idx, cpuc->active_mask)) + continue; rdmsrl(MSR_K7_EVNTSEL0 + idx, val); - if (val & ARCH_PERFMON_EVENTSEL0_ENABLE) { - val &= ~ARCH_PERFMON_EVENTSEL0_ENABLE; - wrmsrl(MSR_K7_EVNTSEL0 + idx, val); - } + if (!(val & ARCH_PERFMON_EVENTSEL0_ENABLE)) + continue; + val &= ~ARCH_PERFMON_EVENTSEL0_ENABLE; + wrmsrl(MSR_K7_EVNTSEL0 + idx, val); } return enabled; @@ -372,13 +374,15 @@ static void pmc_amd_restore_all(u64 ctrl) return; for (idx = 0; idx < nr_counters_generic; idx++) { - if (test_bit(idx, cpuc->active_mask)) { - u64 val; + u64 val; - rdmsrl(MSR_K7_EVNTSEL0 + idx, val); - val |= ARCH_PERFMON_EVENTSEL0_ENABLE; - wrmsrl(MSR_K7_EVNTSEL0 + idx, val); - } + if (!test_bit(idx, cpuc->active_mask)) + continue; + rdmsrl(MSR_K7_EVNTSEL0 + idx, val); + if (val & ARCH_PERFMON_EVENTSEL0_ENABLE) + continue; + val |= ARCH_PERFMON_EVENTSEL0_ENABLE; + wrmsrl(MSR_K7_EVNTSEL0 + idx, val); } } |