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authorStephane Eranian <eranian@google.com>2012-02-09 23:21:00 +0100
committerIngo Molnar <mingo@elte.hu>2012-03-05 14:55:42 +0100
commitd010b3326cf06b3406cdd88af16dcf4e4b6fec2e (patch)
treed0468d78582aeff6a603cb5d29b1a14310106896 /arch/x86/kernel/cpu
parent2481c5fa6db0237e4f0168f88913178b2b495b7c (diff)
perf: Add callback to flush branch_stack on context switch
With branch stack sampling, it is possible to filter by priv levels. In system-wide mode, that means it is possible to capture only user level branches. The builtin SW LBR filter needs to disassemble code based on LBR captured addresses. For that, it needs to know the task the addresses are associated with. Because of context switches, the content of the branch stack buffer may contain addresses from different tasks. We need a callback on context switch to either flush the branch stack or save it. This patch adds a new callback in struct pmu which is called during context switches. The callback is called only when necessary. That is when a system-wide context has, at least, one event which uses PERF_SAMPLE_BRANCH_STACK. The callback is never called for per-thread context. In this version, the Intel x86 code simply flushes (resets) the LBR on context switches (fills it with zeroes). Those zeroed branches are then filtered out by the SW filter. Signed-off-by: Stephane Eranian <eranian@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1328826068-11713-11-git-send-email-eranian@google.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/cpu')
-rw-r--r--arch/x86/kernel/cpu/perf_event.c21
-rw-r--r--arch/x86/kernel/cpu/perf_event.h1
-rw-r--r--arch/x86/kernel/cpu/perf_event_intel.c13
3 files changed, 28 insertions, 7 deletions
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index cea56748327..0a18d16cb58 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1671,25 +1671,32 @@ static const struct attribute_group *x86_pmu_attr_groups[] = {
NULL,
};
+static void x86_pmu_flush_branch_stack(void)
+{
+ if (x86_pmu.flush_branch_stack)
+ x86_pmu.flush_branch_stack();
+}
+
static struct pmu pmu = {
- .pmu_enable = x86_pmu_enable,
- .pmu_disable = x86_pmu_disable,
+ .pmu_enable = x86_pmu_enable,
+ .pmu_disable = x86_pmu_disable,
.attr_groups = x86_pmu_attr_groups,
.event_init = x86_pmu_event_init,
- .add = x86_pmu_add,
- .del = x86_pmu_del,
- .start = x86_pmu_start,
- .stop = x86_pmu_stop,
- .read = x86_pmu_read,
+ .add = x86_pmu_add,
+ .del = x86_pmu_del,
+ .start = x86_pmu_start,
+ .stop = x86_pmu_stop,
+ .read = x86_pmu_read,
.start_txn = x86_pmu_start_txn,
.cancel_txn = x86_pmu_cancel_txn,
.commit_txn = x86_pmu_commit_txn,
.event_idx = x86_pmu_event_idx,
+ .flush_branch_stack = x86_pmu_flush_branch_stack,
};
void perf_update_user_clock(struct perf_event_mmap_page *userpg, u64 now)
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index f104c054dc5..74387c12dc7 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -324,6 +324,7 @@ struct x86_pmu {
void (*cpu_starting)(int cpu);
void (*cpu_dying)(int cpu);
void (*cpu_dead)(int cpu);
+ void (*flush_branch_stack)(void);
/*
* Intel Arch Perfmon v2+
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 7cc1e2dcc4d..6627089232a 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1539,6 +1539,18 @@ 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();
+}
+
static __initconst const struct x86_pmu intel_pmu = {
.name = "Intel",
.handle_irq = intel_pmu_handle_irq,
@@ -1566,6 +1578,7 @@ 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,
};
static __init void intel_clovertown_quirk(void)