perf_counter: Add fork event

Create a fork event so that we can easily clone the comm and
dso maps without having to generate all those events.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 116 insertions, 19 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index b7d7a9f0bd7a..f4466ca37ece 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1412,12 +1412,12 @@ long do_fork(unsigned long clone_flags,
                 if (clone_flags & CLONE_VFORK) {
                         p->vfork_done = &vfork;
                         init_completion(&vfork);
-                } else {
+                } else if (!(clone_flags & CLONE_VM)) {
                         /*
                          * vfork will do an exec which will call
                          * set_task_comm()
                          */
-                        perf_counter_comm(p);
+                        perf_counter_fork(p);
                 }
 
                 audit_finish_fork(p);
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 0bb03f15a5b6..78c58623a0dd 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -40,9 +40,9 @@ static int perf_reserved_percpu __read_mostly;
 static int perf_overcommit __read_mostly = 1;
 
 static atomic_t nr_counters __read_mostly;
-static atomic_t nr_mmap_tracking __read_mostly;
-static atomic_t nr_munmap_tracking __read_mostly;
-static atomic_t nr_comm_tracking __read_mostly;
+static atomic_t nr_mmap_counters __read_mostly;
+static atomic_t nr_munmap_counters __read_mostly;
+static atomic_t nr_comm_counters __read_mostly;
 
 int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */
 int sysctl_perf_counter_mlock __read_mostly = 512; /* 'free' kb per user */
@@ -1447,11 +1447,11 @@ static void free_counter(struct perf_counter *counter)
 
         atomic_dec(&nr_counters);
         if (counter->attr.mmap)
-                atomic_dec(&nr_mmap_tracking);
+                atomic_dec(&nr_mmap_counters);
         if (counter->attr.munmap)
-                atomic_dec(&nr_munmap_tracking);
+                atomic_dec(&nr_munmap_counters);
         if (counter->attr.comm)
-                atomic_dec(&nr_comm_tracking);
+                atomic_dec(&nr_comm_counters);
 
         if (counter->destroy)
                 counter->destroy(counter);
@@ -2476,6 +2476,105 @@ static void perf_counter_output(struct perf_counter *counter,
 }
 
 /*
+ * fork tracking
+ */
+
+struct perf_fork_event {
+        struct task_struct      *task;
+
+        struct {
+                struct perf_event_header        header;
+
+                u32                             pid;
+                u32                             ppid;
+        } event;
+};
+
+static void perf_counter_fork_output(struct perf_counter *counter,
+                                     struct perf_fork_event *fork_event)
+{
+        struct perf_output_handle handle;
+        int size = fork_event->event.header.size;
+        struct task_struct *task = fork_event->task;
+        int ret = perf_output_begin(&handle, counter, size, 0, 0);
+
+        if (ret)
+                return;
+
+        fork_event->event.pid = perf_counter_pid(counter, task);
+        fork_event->event.ppid = perf_counter_pid(counter, task->real_parent);
+
+        perf_output_put(&handle, fork_event->event);
+        perf_output_end(&handle);
+}
+
+static int perf_counter_fork_match(struct perf_counter *counter)
+{
+        if (counter->attr.comm || counter->attr.mmap || counter->attr.munmap)
+                return 1;
+
+        return 0;
+}
+
+static void perf_counter_fork_ctx(struct perf_counter_context *ctx,
+                                  struct perf_fork_event *fork_event)
+{
+        struct perf_counter *counter;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(counter, &ctx->event_list, event_entry) {
+                if (perf_counter_fork_match(counter))
+                        perf_counter_fork_output(counter, fork_event);
+        }
+        rcu_read_unlock();
+}
+
+static void perf_counter_fork_event(struct perf_fork_event *fork_event)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_counter_context *ctx;
+
+        cpuctx = &get_cpu_var(perf_cpu_context);
+        perf_counter_fork_ctx(&cpuctx->ctx, fork_event);
+        put_cpu_var(perf_cpu_context);
+
+        rcu_read_lock();
+        /*
+         * doesn't really matter which of the child contexts the
+         * events ends up in.
+         */
+        ctx = rcu_dereference(current->perf_counter_ctxp);
+        if (ctx)
+                perf_counter_fork_ctx(ctx, fork_event);
+        rcu_read_unlock();
+}
+
+void perf_counter_fork(struct task_struct *task)
+{
+        struct perf_fork_event fork_event;
+
+        if (!atomic_read(&nr_comm_counters) &&
+            !atomic_read(&nr_mmap_counters) &&
+            !atomic_read(&nr_munmap_counters))
+                return;
+
+        fork_event = (struct perf_fork_event){
+                .task   = task,
+                .event  = {
+                        .header = {
+                                .type = PERF_EVENT_FORK,
+                                .size = sizeof(fork_event.event),
+                        },
+                },
+        };
+
+        perf_counter_fork_event(&fork_event);
+}
+
+/*
  * comm tracking
  */
 
@@ -2511,11 +2610,9 @@ static void perf_counter_comm_output(struct perf_counter *counter,
         perf_output_end(&handle);
 }
 
-static int perf_counter_comm_match(struct perf_counter *counter,
-                                   struct perf_comm_event *comm_event)
+static int perf_counter_comm_match(struct perf_counter *counter)
 {
-        if (counter->attr.comm &&
-            comm_event->event.header.type == PERF_EVENT_COMM)
+        if (counter->attr.comm)
                 return 1;
 
         return 0;
@@ -2531,7 +2628,7 @@ static void perf_counter_comm_ctx(struct perf_counter_context *ctx,
 
         rcu_read_lock();
         list_for_each_entry_rcu(counter, &ctx->event_list, event_entry) {
-                if (perf_counter_comm_match(counter, comm_event))
+                if (perf_counter_comm_match(counter))
                         perf_counter_comm_output(counter, comm_event);
         }
         rcu_read_unlock();
@@ -2570,7 +2667,7 @@ void perf_counter_comm(struct task_struct *task)
 {
         struct perf_comm_event comm_event;
 
-        if (!atomic_read(&nr_comm_tracking))
+        if (!atomic_read(&nr_comm_counters))
                 return;
 
         comm_event = (struct perf_comm_event){
@@ -2708,7 +2805,7 @@ void perf_counter_mmap(unsigned long addr, unsigned long len,
 {
         struct perf_mmap_event mmap_event;
 
-        if (!atomic_read(&nr_mmap_tracking))
+        if (!atomic_read(&nr_mmap_counters))
                 return;
 
         mmap_event = (struct perf_mmap_event){
@@ -2729,7 +2826,7 @@ void perf_counter_munmap(unsigned long addr, unsigned long len,
 {
         struct perf_mmap_event mmap_event;
 
-        if (!atomic_read(&nr_munmap_tracking))
+        if (!atomic_read(&nr_munmap_counters))
                 return;
 
         mmap_event = (struct perf_mmap_event){
@@ -3427,11 +3524,11 @@ done:
 
         atomic_inc(&nr_counters);
         if (counter->attr.mmap)
-                atomic_inc(&nr_mmap_tracking);
+                atomic_inc(&nr_mmap_counters);
         if (counter->attr.munmap)
-                atomic_inc(&nr_munmap_tracking);
+                atomic_inc(&nr_munmap_counters);
         if (counter->attr.comm)
-                atomic_inc(&nr_comm_tracking);
+                atomic_inc(&nr_comm_counters);
 
         return counter;
 }