From 421ca868ea3b7c1ca1a541ed6dff3c101a563b95 Mon Sep 17 00:00:00 2001 From: Alexey Budankov Date: Wed, 23 Oct 2019 10:12:54 +0300 Subject: [PATCH] perf/x86/intel: Implement LBR callstack context synchronization Implement intel_pmu_lbr_swap_task_ctx() method updating counters of the events that requested LBR callstack data on a sample. The counter can be zero for the case when task context belongs to a thread that has just come from a block on a futex and the context contains saved (lbr_stack_state == LBR_VALID) LBR register values. For the values to be restored at LBR registers on the next thread's switch-in event it swaps the counter value with the one that is expected to be non zero at the previous equivalent task perf event context. Swap operation type ensures the previous task perf event context stays consistent with the amount of events that requested LBR callstack data on a sample. Signed-off-by: Alexey Budankov Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Ian Rogers Cc: Jiri Olsa Cc: Kan Liang Cc: Linus Torvalds Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Song Liu Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Link: https://lkml.kernel.org/r/261ac742-9022-c3f4-5885-1eae7415b091@linux.intel.com Signed-off-by: Ingo Molnar --- arch/x86/events/intel/lbr.c | 23 +++++++++++++++++++++++ arch/x86/events/perf_event.h | 3 +++ 2 files changed, 26 insertions(+) diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c index ea54634eabf3..534c76606049 100644 --- a/arch/x86/events/intel/lbr.c +++ b/arch/x86/events/intel/lbr.c @@ -417,6 +417,29 @@ static void __intel_pmu_lbr_save(struct x86_perf_task_context *task_ctx) cpuc->last_log_id = ++task_ctx->log_id; } +void intel_pmu_lbr_swap_task_ctx(struct perf_event_context *prev, + struct perf_event_context *next) +{ + struct x86_perf_task_context *prev_ctx_data, *next_ctx_data; + + swap(prev->task_ctx_data, next->task_ctx_data); + + /* + * Architecture specific synchronization makes sense in + * case both prev->task_ctx_data and next->task_ctx_data + * pointers are allocated. + */ + + prev_ctx_data = next->task_ctx_data; + next_ctx_data = prev->task_ctx_data; + + if (!prev_ctx_data || !next_ctx_data) + return; + + swap(prev_ctx_data->lbr_callstack_users, + next_ctx_data->lbr_callstack_users); +} + void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in) { struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h index 5384317eaa16..930611db8f9a 100644 --- a/arch/x86/events/perf_event.h +++ b/arch/x86/events/perf_event.h @@ -1024,6 +1024,9 @@ void intel_pmu_store_pebs_lbrs(struct pebs_lbr *lbr); void intel_ds_init(void); +void intel_pmu_lbr_swap_task_ctx(struct perf_event_context *prev, + struct perf_event_context *next); + void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in); u64 lbr_from_signext_quirk_wr(u64 val); -- 2.30.2