perf_counter: track task-comm data

Similar to the mmap data stream, add one that tracks the task COMM field,
so that the userspace reporting knows what to call a task.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090408130409.127422406@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 93 insertions, 0 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index bf12df6f3538..2d4aebb2982b 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1917,6 +1917,99 @@ static void perf_counter_output(struct perf_counter *counter,
 }
 
 /*
+ * comm tracking
+ */
+
+struct perf_comm_event {
+        struct task_struct      *task;
+        char                    *comm;
+        int                     comm_size;
+
+        struct {
+                struct perf_event_header        header;
+
+                u32                             pid;
+                u32                             tid;
+        } event;
+};
+
+static void perf_counter_comm_output(struct perf_counter *counter,
+                                     struct perf_comm_event *comm_event)
+{
+        struct perf_output_handle handle;
+        int size = comm_event->event.header.size;
+        int ret = perf_output_begin(&handle, counter, size, 0, 0);
+
+        if (ret)
+                return;
+
+        perf_output_put(&handle, comm_event->event);
+        perf_output_copy(&handle, comm_event->comm,
+                                   comm_event->comm_size);
+        perf_output_end(&handle);
+}
+
+static int perf_counter_comm_match(struct perf_counter *counter,
+                                   struct perf_comm_event *comm_event)
+{
+        if (counter->hw_event.comm &&
+            comm_event->event.header.type == PERF_EVENT_COMM)
+                return 1;
+
+        return 0;
+}
+
+static void perf_counter_comm_ctx(struct perf_counter_context *ctx,
+                                  struct perf_comm_event *comm_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_comm_match(counter, comm_event))
+                        perf_counter_comm_output(counter, comm_event);
+        }
+        rcu_read_unlock();
+}
+
+static void perf_counter_comm_event(struct perf_comm_event *comm_event)
+{
+        struct perf_cpu_context *cpuctx;
+        unsigned int size;
+        char *comm = comm_event->task->comm;
+
+        size = ALIGN(strlen(comm), sizeof(u64));
+
+        comm_event->comm = comm;
+        comm_event->comm_size = size;
+
+        comm_event->event.header.size = sizeof(comm_event->event) + size;
+
+        cpuctx = &get_cpu_var(perf_cpu_context);
+        perf_counter_comm_ctx(&cpuctx->ctx, comm_event);
+        put_cpu_var(perf_cpu_context);
+
+        perf_counter_comm_ctx(&current->perf_counter_ctx, comm_event);
+}
+
+void perf_counter_comm(struct task_struct *task)
+{
+        struct perf_comm_event comm_event = {
+                .task   = task,
+                .event  = {
+                        .header = { .type = PERF_EVENT_COMM, },
+                        .pid    = task->group_leader->pid,
+                        .tid    = task->pid,
+                },
+        };
+
+        perf_counter_comm_event(&comm_event);
+}
+
+/*
  * mmap tracking
  */