Messages in this thread Patch in this message | | | Subject | [PATCH v3 4/4] perf/core,x86: synchronize PMU task contexts on optimized context switches | From | Alexey Budankov <> | Date | Fri, 18 Oct 2019 12:45:11 +0300 |
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Install Intel specific PMU task context synchronization adapter and extend optimized context switch path with PMU specific task context synchronization to fix LBR callstack virtualization on context switches.
Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com> --- arch/x86/events/intel/core.c | 7 +++++++ kernel/events/core.c | 9 +++++++++ 2 files changed, 16 insertions(+)
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 43c966d1208e..7cfa658cce4b 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3819,6 +3819,12 @@ static void intel_pmu_sched_task(struct perf_event_context *ctx, intel_pmu_lbr_sched_task(ctx, sched_in); } +static void intel_pmu_sync_task_ctx(struct x86_perf_task_context *one, + struct x86_perf_task_context *another) +{ + intel_pmu_lbr_sync_task_ctx(one, another); +} + static int intel_pmu_check_period(struct perf_event *event, u64 value) { return intel_pmu_has_bts_period(event, value) ? -EINVAL : 0; @@ -3954,6 +3960,7 @@ static __initconst const struct x86_pmu intel_pmu = { .guest_get_msrs = intel_guest_get_msrs, .sched_task = intel_pmu_sched_task, + .sync_task_ctx = intel_pmu_sync_task_ctx, .check_period = intel_pmu_check_period, diff --git a/kernel/events/core.c b/kernel/events/core.c index 2aad959e6def..3c7edd8454ef 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3204,11 +3204,20 @@ static void perf_event_context_sched_out(struct task_struct *task, int ctxn, raw_spin_lock(&ctx->lock); raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING); if (context_equiv(ctx, next_ctx)) { + struct pmu *pmu = ctx->pmu; + WRITE_ONCE(ctx->task, next); WRITE_ONCE(next_ctx->task, task); swap(ctx->task_ctx_data, next_ctx->task_ctx_data); + /* + * PMU specific parts of task perf context may require + * additional synchronization, at least for proper Intel + * LBR callstack data profiling; + */ + pmu->sync_task_ctx(ctx->task_ctx_data, + next_ctx->task_ctx_data); /* * RCU_INIT_POINTER here is safe because we've not * modified the ctx and the above modification of -- 2.20.1
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