perf, trace: Optimize tracepoints by using per-tracepoint-per-cpu hlist to track events

Avoid the swevent hash-table by using per-tracepoint
hlists.

Also, avoid conditionals on the fast path by ordering
with probe unregister so that we should never get on
the callback path without the data being there.

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: <20100521090710.473188012@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 67 insertions, 60 deletions

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index a1304f8c444..39d5ea7b065 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -23,14 +23,25 @@ typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
 /* Count the events in use (per event id, not per instance) */
 static int      total_ref_count;
 
-static int perf_trace_event_enable(struct ftrace_event_call *event, void *data)
+static int perf_trace_event_init(struct ftrace_event_call *tp_event,
+                                 struct perf_event *p_event)
 {
+        struct hlist_head *list;
         int ret = -ENOMEM;
+        int cpu;
 
-        if (event->perf_refcount++ > 0) {
-                event->perf_data = NULL;
+        p_event->tp_event = tp_event;
+        if (tp_event->perf_refcount++ > 0)
                 return 0;
-        }
+
+        list = alloc_percpu(struct hlist_head);
+        if (!list)
+                goto fail;
+
+        for_each_possible_cpu(cpu)
+                INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
+
+        tp_event->perf_events = list;
 
         if (!total_ref_count) {
                 char *buf;
@@ -39,20 +50,20 @@ static int perf_trace_event_enable(struct ftrace_event_call *event, void *data)
                 for (i = 0; i < 4; i++) {
                         buf = (char *)alloc_percpu(perf_trace_t);
                         if (!buf)
-                                goto fail_buf;
+                                goto fail;
 
-                        rcu_assign_pointer(perf_trace_buf[i], buf);
+                        perf_trace_buf[i] = buf;
                 }
         }
 
-        ret = event->perf_event_enable(event);
-        if (!ret) {
-                event->perf_data = data;
-                total_ref_count++;
-                return 0;
-        }
+        ret = tp_event->perf_event_enable(tp_event);
+        if (ret)
+                goto fail;
 
-fail_buf:
+        total_ref_count++;
+        return 0;
+
+fail:
         if (!total_ref_count) {
                 int i;
 
@@ -61,21 +72,26 @@ fail_buf:
                         perf_trace_buf[i] = NULL;
                 }
         }
-        event->perf_refcount--;
+
+        if (!--tp_event->perf_refcount) {
+                free_percpu(tp_event->perf_events);
+                tp_event->perf_events = NULL;
+        }
 
         return ret;
 }
 
-int perf_trace_enable(int event_id, void *data)
+int perf_trace_init(struct perf_event *p_event)
 {
-        struct ftrace_event_call *event;
+        struct ftrace_event_call *tp_event;
+        int event_id = p_event->attr.config;
         int ret = -EINVAL;
 
         mutex_lock(&event_mutex);
-        list_for_each_entry(event, &ftrace_events, list) {
-                if (event->id == event_id && event->perf_event_enable &&
-                    try_module_get(event->mod)) {
-                        ret = perf_trace_event_enable(event, data);
+        list_for_each_entry(tp_event, &ftrace_events, list) {
+                if (tp_event->id == event_id && tp_event->perf_event_enable &&
+                    try_module_get(tp_event->mod)) {
+                        ret = perf_trace_event_init(tp_event, p_event);
                         break;
                 }
         }
@@ -84,53 +100,52 @@ int perf_trace_enable(int event_id, void *data)
         return ret;
 }
 
-static void perf_trace_event_disable(struct ftrace_event_call *event)
+int perf_trace_enable(struct perf_event *p_event)
 {
-        if (--event->perf_refcount > 0)
-                return;
+        struct ftrace_event_call *tp_event = p_event->tp_event;
+        struct hlist_head *list;
 
-        event->perf_event_disable(event);
+        list = tp_event->perf_events;
+        if (WARN_ON_ONCE(!list))
+                return -EINVAL;
 
-        if (!--total_ref_count) {
-                char *buf[4];
-                int i;
-
-                for (i = 0; i < 4; i++) {
-                        buf[i] = perf_trace_buf[i];
-                        rcu_assign_pointer(perf_trace_buf[i], NULL);
-                }
+        list = per_cpu_ptr(list, smp_processor_id());
+        hlist_add_head_rcu(&p_event->hlist_entry, list);
 
-                /*
-                 * Ensure every events in profiling have finished before
-                 * releasing the buffers
-                 */
-                synchronize_sched();
+        return 0;
+}
 
-                for (i = 0; i < 4; i++)
-                        free_percpu(buf[i]);
-        }
+void perf_trace_disable(struct perf_event *p_event)
+{
+        hlist_del_rcu(&p_event->hlist_entry);
 }
 
-void perf_trace_disable(int event_id)
+void perf_trace_destroy(struct perf_event *p_event)
 {
-        struct ftrace_event_call *event;
+        struct ftrace_event_call *tp_event = p_event->tp_event;
+        int i;
 
-        mutex_lock(&event_mutex);
-        list_for_each_entry(event, &ftrace_events, list) {
-                if (event->id == event_id) {
-                        perf_trace_event_disable(event);
-                        module_put(event->mod);
-                        break;
+        if (--tp_event->perf_refcount > 0)
+                return;
+
+        tp_event->perf_event_disable(tp_event);
+
+        free_percpu(tp_event->perf_events);
+        tp_event->perf_events = NULL;
+
+        if (!--total_ref_count) {
+                for (i = 0; i < 4; i++) {
+                        free_percpu(perf_trace_buf[i]);
+                        perf_trace_buf[i] = NULL;
                 }
         }
-        mutex_unlock(&event_mutex);
 }
 
 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
                                        struct pt_regs *regs, int *rctxp)
 {
         struct trace_entry *entry;
-        char *trace_buf, *raw_data;
+        char *raw_data;
         int pc;
 
         BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
@@ -139,13 +154,9 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
 
         *rctxp = perf_swevent_get_recursion_context();
         if (*rctxp < 0)
-                goto err_recursion;
-
-        trace_buf = rcu_dereference_sched(perf_trace_buf[*rctxp]);
-        if (!trace_buf)
-                goto err;
+                return NULL;
 
-        raw_data = per_cpu_ptr(trace_buf, smp_processor_id());
+        raw_data = per_cpu_ptr(perf_trace_buf[*rctxp], smp_processor_id());
 
         /* zero the dead bytes from align to not leak stack to user */
         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
@@ -155,9 +166,5 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
         entry->type = type;
 
         return raw_data;
-err:
-        perf_swevent_put_recursion_context(*rctxp);
-err_recursion:
-        return NULL;
 }
 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);