forked from Minki/linux
6c1c07b33e
The perf PMI handler, intel_pmu_handle_irq(), currently does unnecessary MSR accesses for PEBS_ENABLE MSR in __intel_pmu_enable/disable_all() when PEBS is enabled. When entering the handler, global ctrl is explicitly disabled. All counters do not count anymore. It doesn't matter if PEBS is enabled or not in a PMI handler. Furthermore, for most cases, the cpuc->pebs_enabled is not changed in PMI. The PEBS status doesn't change. The PEBS_ENABLE MSR doesn't need to be changed either when exiting the handler. PMI throttle may change the PEBS status during PMI handler. The x86_pmu_stop() ends up in intel_pmu_pebs_disable() which can update cpuc->pebs_enabled. But the MSR_IA32_PEBS_ENABLE is not updated at the same time. Because the cpuc->enabled has been forced to 0. The patch explicitly update the MSR_IA32_PEBS_ENABLE for this case. Use ftrace to measure the duration of intel_pmu_handle_irq() on BDX. #perf record -e cycles:P -- ./tchain_edit The average duration of intel_pmu_handle_irq(): Without the patch 1.144 us With the patch 1.025 us Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20200121181338.3234-1-kan.liang@linux.intel.com |
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| .. | ||
| amd | ||
| intel | ||
| core.c | ||
| Kconfig | ||
| Makefile | ||
| msr.c | ||
| perf_event.h | ||
| probe.c | ||
| probe.h | ||