From 2a0ad3b326a9024ba86dca4028499d31fa0c6c4d Mon Sep 17 00:00:00 2001 From: "Yan, Zheng" Date: Tue, 4 Nov 2014 21:55:59 -0500 Subject: [PATCH] perf/x86/intel: Use context switch callback to flush LBR stack Previous commit introduces context switch callback, its function overlaps with the flush branch stack callback. So we can use the context switch callback to flush LBR stack. This patch adds code that uses the flush branch callback to flush the LBR stack when task is being scheduled in. The callback is enabled only when there are events use the LBR hardware. This patch also removes all old flush branch stack code. Signed-off-by: Yan, Zheng Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Cc: Paul Mackerras Cc: Vince Weaver Cc: eranian@google.com Cc: jolsa@redhat.com Link: http://lkml.kernel.org/r/1415156173-10035-4-git-send-email-kan.liang@intel.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event.c | 7 -- arch/x86/kernel/cpu/perf_event.h | 3 +- arch/x86/kernel/cpu/perf_event_intel.c | 14 +--- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 27 ++++++++ include/linux/perf_event.h | 1 - kernel/events/core.c | 77 ---------------------- 6 files changed, 30 insertions(+), 99 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 0efbd6cc2966..6b1fd26a37cf 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -1920,12 +1920,6 @@ static void x86_pmu_sched_task(struct perf_event_context *ctx, bool sched_in) x86_pmu.sched_task(ctx, sched_in); } -static void x86_pmu_flush_branch_stack(void) -{ - if (x86_pmu.flush_branch_stack) - x86_pmu.flush_branch_stack(); -} - void perf_check_microcode(void) { if (x86_pmu.check_microcode) @@ -1955,7 +1949,6 @@ static struct pmu pmu = { .commit_txn = x86_pmu_commit_txn, .event_idx = x86_pmu_event_idx, - .flush_branch_stack = x86_pmu_flush_branch_stack, .sched_task = x86_pmu_sched_task, }; diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h index 211b54c0c00c..949d0083a29e 100644 --- a/arch/x86/kernel/cpu/perf_event.h +++ b/arch/x86/kernel/cpu/perf_event.h @@ -472,7 +472,6 @@ struct x86_pmu { void (*cpu_dead)(int cpu); void (*check_microcode)(void); - void (*flush_branch_stack)(void); void (*sched_task)(struct perf_event_context *ctx, bool sched_in); @@ -733,6 +732,8 @@ void intel_pmu_pebs_disable_all(void); void intel_ds_init(void); +void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in); + void intel_pmu_lbr_reset(void); void intel_pmu_lbr_enable(struct perf_event *event); diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c index 498b6d967138..424fbf74dee7 100644 --- a/arch/x86/kernel/cpu/perf_event_intel.c +++ b/arch/x86/kernel/cpu/perf_event_intel.c @@ -2044,18 +2044,6 @@ static void intel_pmu_cpu_dying(int cpu) fini_debug_store_on_cpu(cpu); } -static void intel_pmu_flush_branch_stack(void) -{ - /* - * Intel LBR does not tag entries with the - * PID of the current task, then we need to - * flush it on ctxsw - * For now, we simply reset it - */ - if (x86_pmu.lbr_nr) - intel_pmu_lbr_reset(); -} - PMU_FORMAT_ATTR(offcore_rsp, "config1:0-63"); PMU_FORMAT_ATTR(ldlat, "config1:0-15"); @@ -2107,7 +2095,7 @@ static __initconst const struct x86_pmu intel_pmu = { .cpu_starting = intel_pmu_cpu_starting, .cpu_dying = intel_pmu_cpu_dying, .guest_get_msrs = intel_guest_get_msrs, - .flush_branch_stack = intel_pmu_flush_branch_stack, + .sched_task = intel_pmu_lbr_sched_task, }; static __init void intel_clovertown_quirk(void) diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index 8bc078f43a82..c0e23c5f85bb 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -177,6 +177,31 @@ void intel_pmu_lbr_reset(void) intel_pmu_lbr_reset_64(); } +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); + + if (!x86_pmu.lbr_nr) + return; + + /* + * When sampling the branck stack in system-wide, it may be + * necessary to flush the stack on context switch. This happens + * when the branch stack does not tag its entries with the pid + * of the current task. Otherwise it becomes impossible to + * associate a branch entry with a task. This ambiguity is more + * likely to appear when the branch stack supports priv level + * filtering and the user sets it to monitor only at the user + * level (which could be a useful measurement in system-wide + * mode). In that case, the risk is high of having a branch + * stack with branch from multiple tasks. + */ + if (sched_in) { + intel_pmu_lbr_reset(); + cpuc->lbr_context = ctx; + } +} + void intel_pmu_lbr_enable(struct perf_event *event) { struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); @@ -195,6 +220,7 @@ void intel_pmu_lbr_enable(struct perf_event *event) cpuc->br_sel = event->hw.branch_reg.reg; cpuc->lbr_users++; + perf_sched_cb_inc(event->ctx->pmu); } void intel_pmu_lbr_disable(struct perf_event *event) @@ -206,6 +232,7 @@ void intel_pmu_lbr_disable(struct perf_event *event) cpuc->lbr_users--; WARN_ON_ONCE(cpuc->lbr_users < 0); + perf_sched_cb_dec(event->ctx->pmu); if (cpuc->enabled && !cpuc->lbr_users) { __intel_pmu_lbr_disable(); diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index fbab6235d053..c7007a564440 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -511,7 +511,6 @@ struct perf_event_context { u64 generation; int pin_count; int nr_cgroups; /* cgroup evts */ - int nr_branch_stack; /* branch_stack evt */ struct rcu_head rcu_head; struct delayed_work orphans_remove; diff --git a/kernel/events/core.c b/kernel/events/core.c index 6c8b31b7efb6..f563ce767f93 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -153,7 +153,6 @@ enum event_type_t { */ struct static_key_deferred perf_sched_events __read_mostly; static DEFINE_PER_CPU(atomic_t, perf_cgroup_events); -static DEFINE_PER_CPU(atomic_t, perf_branch_stack_events); static DEFINE_PER_CPU(int, perf_sched_cb_usages); static atomic_t nr_mmap_events __read_mostly; @@ -1240,9 +1239,6 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx) if (is_cgroup_event(event)) ctx->nr_cgroups++; - if (has_branch_stack(event)) - ctx->nr_branch_stack++; - list_add_rcu(&event->event_entry, &ctx->event_list); ctx->nr_events++; if (event->attr.inherit_stat) @@ -1409,9 +1405,6 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx) cpuctx->cgrp = NULL; } - if (has_branch_stack(event)) - ctx->nr_branch_stack--; - ctx->nr_events--; if (event->attr.inherit_stat) ctx->nr_stat--; @@ -2808,64 +2801,6 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx, perf_ctx_unlock(cpuctx, ctx); } -/* - * When sampling the branck stack in system-wide, it may be necessary - * to flush the stack on context switch. This happens when the branch - * stack does not tag its entries with the pid of the current task. - * Otherwise it becomes impossible to associate a branch entry with a - * task. This ambiguity is more likely to appear when the branch stack - * supports priv level filtering and the user sets it to monitor only - * at the user level (which could be a useful measurement in system-wide - * mode). In that case, the risk is high of having a branch stack with - * branch from multiple tasks. Flushing may mean dropping the existing - * entries or stashing them somewhere in the PMU specific code layer. - * - * This function provides the context switch callback to the lower code - * layer. It is invoked ONLY when there is at least one system-wide context - * with at least one active event using taken branch sampling. - */ -static void perf_branch_stack_sched_in(struct task_struct *prev, - struct task_struct *task) -{ - struct perf_cpu_context *cpuctx; - struct pmu *pmu; - unsigned long flags; - - /* no need to flush branch stack if not changing task */ - if (prev == task) - return; - - local_irq_save(flags); - - rcu_read_lock(); - - list_for_each_entry_rcu(pmu, &pmus, entry) { - cpuctx = this_cpu_ptr(pmu->pmu_cpu_context); - - /* - * check if the context has at least one - * event using PERF_SAMPLE_BRANCH_STACK - */ - if (cpuctx->ctx.nr_branch_stack > 0 - && pmu->flush_branch_stack) { - - perf_ctx_lock(cpuctx, cpuctx->task_ctx); - - perf_pmu_disable(pmu); - - pmu->flush_branch_stack(); - - perf_pmu_enable(pmu); - - perf_ctx_unlock(cpuctx, cpuctx->task_ctx); - } - } - - rcu_read_unlock(); - - local_irq_restore(flags); -} - /* * Called from scheduler to add the events of the current task * with interrupts disabled. @@ -2898,10 +2833,6 @@ void __perf_event_task_sched_in(struct task_struct *prev, if (atomic_read(this_cpu_ptr(&perf_cgroup_events))) perf_cgroup_sched_in(prev, task); - /* check for system-wide branch_stack events */ - if (atomic_read(this_cpu_ptr(&perf_branch_stack_events))) - perf_branch_stack_sched_in(prev, task); - if (__this_cpu_read(perf_sched_cb_usages)) perf_pmu_sched_task(prev, task, true); } @@ -3480,10 +3411,6 @@ static void unaccount_event_cpu(struct perf_event *event, int cpu) if (event->parent) return; - if (has_branch_stack(event)) { - if (!(event->attach_state & PERF_ATTACH_TASK)) - atomic_dec(&per_cpu(perf_branch_stack_events, cpu)); - } if (is_cgroup_event(event)) atomic_dec(&per_cpu(perf_cgroup_events, cpu)); } @@ -7139,10 +7066,6 @@ static void account_event_cpu(struct perf_event *event, int cpu) if (event->parent) return; - if (has_branch_stack(event)) { - if (!(event->attach_state & PERF_ATTACH_TASK)) - atomic_inc(&per_cpu(perf_branch_stack_events, cpu)); - } if (is_cgroup_event(event)) atomic_inc(&per_cpu(perf_cgroup_events, cpu)); } -- 2.20.1