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author | Mark Rutland <mark.rutland@arm.com> | 2016-04-26 11:33:46 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2016-05-05 10:13:59 +0200 |
commit | 5101ef20f0ef1de79091a1fdb6b1a7f07565545a (patch) | |
tree | e258e92de18196699b547763bed143d74e812387 /drivers/perf | |
parent | 6e855cd4f4b5258016cf707f94f96bfa51c32f32 (diff) | |
download | linux-5101ef20f0ef1de79091a1fdb6b1a7f07565545a.tar.gz |
perf/arm: Special-case hetereogeneous CPUs
Commit: 26657848502b7847 ("perf/core: Verify we have a single perf_hw_context PMU") forcefully prevents multiple PMUs from sharing perf_hw_context, as this generally doesn't make sense. It is a common bug for uncore PMUs to use perf_hw_context rather than perf_invalid_context, which this detects. However, systems exist with heterogeneous CPUs (and hence heterogeneous HW PMUs), for which sharing perf_hw_context is necessary, and possible in some limited cases. To make this work we have to perform some gymnastics, as we did in these commits: 66eb579e66ecfea5 ("perf: allow for PMU-specific event filtering") c904e32a69b7c779 ("arm: perf: filter unschedulable events") To allow those systems to work, we must allow PMUs for heterogeneous CPUs to share perf_hw_context, though we must still disallow sharing otherwise to detect the common misuse of perf_hw_context. This patch adds a new PERF_PMU_CAP_HETEROGENEOUS_CPUS for this, updates the core logic to account for this, and makes use of it in the arm_pmu code that is used for systems with heterogeneous CPUs. Comments are added to make the rationale clear and hopefully avoid accidental abuse. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/20160426103346.GA20836@leverpostej Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'drivers/perf')
-rw-r--r-- | drivers/perf/arm_pmu.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c index f70090897fdf..f2d01d4d9364 100644 --- a/drivers/perf/arm_pmu.c +++ b/drivers/perf/arm_pmu.c @@ -847,6 +847,14 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu) if (!platform_get_irq(cpu_pmu->plat_device, 0)) cpu_pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT; + /* + * This is a CPU PMU potentially in a heterogeneous configuration (e.g. + * big.LITTLE). This is not an uncore PMU, and we have taken ctx + * sharing into account (e.g. with our pmu::filter_match callback and + * pmu::event_init group validation). + */ + cpu_pmu->pmu.capabilities |= PERF_PMU_CAP_HETEROGENEOUS_CPUS; + return 0; out_unregister: |