perf, trace: Optimize tracepoints by removing IRQ-disable from perf/tracepoint interaction

Improves performance.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1274259525.5605.10352.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 29 insertions, 44 deletions

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 89b780a7c52..a1304f8c444 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -9,13 +9,9 @@
 #include <linux/kprobes.h>
 #include "trace.h"
 
-DEFINE_PER_CPU(struct pt_regs, perf_trace_regs);
-EXPORT_PER_CPU_SYMBOL_GPL(perf_trace_regs);
-
 EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs);
 
-static char *perf_trace_buf;
-static char *perf_trace_buf_nmi;
+static char *perf_trace_buf[4];
 
 /*
  * Force it to be aligned to unsigned long to avoid misaligned accesses
@@ -29,7 +25,6 @@ static int	total_ref_count;
 
 static int perf_trace_event_enable(struct ftrace_event_call *event, void *data)
 {
-	char *buf;
 	int ret = -ENOMEM;
 
 	if (event->perf_refcount++ > 0) {
@@ -38,17 +33,16 @@ static int perf_trace_event_enable(struct ftrace_event_call *event, void *data)
 	}
 
 	if (!total_ref_count) {
-		buf = (char *)alloc_percpu(perf_trace_t);
-		if (!buf)
-			goto fail_buf;
-
-		rcu_assign_pointer(perf_trace_buf, buf);
+		char *buf;
+		int i;
 
-		buf = (char *)alloc_percpu(perf_trace_t);
-		if (!buf)
-			goto fail_buf_nmi;
+		for (i = 0; i < 4; i++) {
+			buf = (char *)alloc_percpu(perf_trace_t);
+			if (!buf)
+				goto fail_buf;
 
-		rcu_assign_pointer(perf_trace_buf_nmi, buf);
+			rcu_assign_pointer(perf_trace_buf[i], buf);
+		}
 	}
 
 	ret = event->perf_event_enable(event);
@@ -58,14 +52,15 @@ static int perf_trace_event_enable(struct ftrace_event_call *event, void *data)
 		return 0;
 	}
 
-fail_buf_nmi:
+fail_buf:
 	if (!total_ref_count) {
-		free_percpu(perf_trace_buf_nmi);
-		free_percpu(perf_trace_buf);
-		perf_trace_buf_nmi = NULL;
-		perf_trace_buf = NULL;
+		int i;
+
+		for (i = 0; i < 4; i++) {
+			free_percpu(perf_trace_buf[i]);
+			perf_trace_buf[i] = NULL;
+		}
 	}
-fail_buf:
 	event->perf_refcount--;
 
 	return ret;
@@ -91,19 +86,19 @@ int perf_trace_enable(int event_id, void *data)
 
 static void perf_trace_event_disable(struct ftrace_event_call *event)
 {
-	char *buf, *nmi_buf;
-
 	if (--event->perf_refcount > 0)
 		return;
 
 	event->perf_event_disable(event);
 
 	if (!--total_ref_count) {
-		buf = perf_trace_buf;
-		rcu_assign_pointer(perf_trace_buf, NULL);
+		char *buf[4];
+		int i;
 
-		nmi_buf = perf_trace_buf_nmi;
-		rcu_assign_pointer(perf_trace_buf_nmi, NULL);
+		for (i = 0; i < 4; i++) {
+			buf[i] = perf_trace_buf[i];
+			rcu_assign_pointer(perf_trace_buf[i], NULL);
+		}
 
 		/*
 		 * Ensure every events in profiling have finished before
@@ -111,8 +106,8 @@ static void perf_trace_event_disable(struct ftrace_event_call *event)
 		 */
 		synchronize_sched();
 
-		free_percpu(buf);
-		free_percpu(nmi_buf);
+		for (i = 0; i < 4; i++)
+			free_percpu(buf[i]);
 	}
 }
 
@@ -132,47 +127,37 @@ void perf_trace_disable(int event_id)
 }
 
 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
-				       int *rctxp, unsigned long *irq_flags)
+				       struct pt_regs *regs, int *rctxp)
 {
 	struct trace_entry *entry;
 	char *trace_buf, *raw_data;
-	int pc, cpu;
+	int pc;
 
 	BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
 
 	pc = preempt_count();
 
-	/* Protect the per cpu buffer, begin the rcu read side */
-	local_irq_save(*irq_flags);
-
 	*rctxp = perf_swevent_get_recursion_context();
 	if (*rctxp < 0)
 		goto err_recursion;
 
-	cpu = smp_processor_id();
-
-	if (in_nmi())
-		trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);
-	else
-		trace_buf = rcu_dereference_sched(perf_trace_buf);
-
+	trace_buf = rcu_dereference_sched(perf_trace_buf[*rctxp]);
 	if (!trace_buf)
 		goto err;
 
-	raw_data = per_cpu_ptr(trace_buf, cpu);
+	raw_data = per_cpu_ptr(trace_buf, smp_processor_id());
 
 	/* zero the dead bytes from align to not leak stack to user */
 	memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
 
 	entry = (struct trace_entry *)raw_data;
-	tracing_generic_entry_update(entry, *irq_flags, pc);
+	tracing_generic_entry_update(entry, regs->flags, pc);
 	entry->type = type;
 
 	return raw_data;
 err:
 	perf_swevent_put_recursion_context(*rctxp);
 err_recursion:
-	local_irq_restore(*irq_flags);
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);