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 89b780a7c522..a1304f8c4440 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);