perf_counter tools: Handle lost events

Make use of the new ->data_tail mechanism to tell kernel-space
about user-space draining the data stream. Emit lost events
(and display them) if they happen.

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>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index e1dfef2..06fdfb8 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -78,10 +78,10 @@ struct mmap_data {
 
 static struct mmap_data                mmap_array[MAX_NR_CPUS][MAX_COUNTERS];
 
-static unsigned int mmap_read_head(struct mmap_data *md)
+static unsigned long mmap_read_head(struct mmap_data *md)
 {
        struct perf_counter_mmap_page *pc = md->base;
-       int head;
+       long head;
 
        head = pc->data_head;
        rmb();
@@ -89,6 +89,17 @@ static unsigned int mmap_read_head(struct mmap_data *md)
        return head;
 }
 
+static void mmap_write_tail(struct mmap_data *md, unsigned long tail)
+{
+       struct perf_counter_mmap_page *pc = md->base;
+
+       /*
+        * ensure all reads are done before we write the tail out.
+        */
+       /* mb(); */
+       pc->data_tail = tail;
+}
+
 static void mmap_read(struct mmap_data *md)
 {
        unsigned int head = mmap_read_head(md);
@@ -109,7 +120,7 @@ static void mmap_read(struct mmap_data *md)
         * In either case, truncate and restart at head.
         */
        diff = head - old;
-       if (diff > md->mask / 2 || diff < 0) {
+       if (diff < 0) {
                struct timeval iv;
                unsigned long msecs;
 
@@ -167,6 +178,7 @@ static void mmap_read(struct mmap_data *md)
        }
 
        md->prev = old;
+       mmap_write_tail(md, old);
 }
 
 static volatile int done = 0;
@@ -424,7 +436,7 @@ try_again:
        mmap_array[nr_cpu][counter].prev = 0;
        mmap_array[nr_cpu][counter].mask = mmap_pages*page_size - 1;
        mmap_array[nr_cpu][counter].base = mmap(NULL, (mmap_pages+1)*page_size,
-                       PROT_READ, MAP_SHARED, fd[nr_cpu][counter], 0);
+                       PROT_READ|PROT_WRITE, MAP_SHARED, fd[nr_cpu][counter], 0);
        if (mmap_array[nr_cpu][counter].base == MAP_FAILED) {
                error("failed to mmap with %d (%s)\n", errno, strerror(errno));
                exit(-1);

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 9a3805f..fe66895 100644 (file)
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -83,6 +83,12 @@ struct period_event {
        __u64 sample_period;
 };
 
+struct lost_event {
+       struct perf_event_header header;
+       __u64 id;
+       __u64 lost;
+};
+
 typedef union event_union {
        struct perf_event_header        header;
        struct ip_event                 ip;
@@ -90,6 +96,7 @@ typedef union event_union {
        struct comm_event               comm;
        struct fork_event               fork;
        struct period_event             period;
+       struct lost_event               lost;
 } event_t;
 
 static LIST_HEAD(dsos);
@@ -1068,7 +1075,8 @@ static unsigned long total = 0,
                     total_mmap = 0,
                     total_comm = 0,
                     total_fork = 0,
-                    total_unknown = 0;
+                    total_unknown = 0,
+                    total_lost = 0;
 
 static int validate_chain(struct perf_callchain_entry *chain, event_t *event)
 {
@@ -1260,6 +1268,20 @@ process_period_event(event_t *event, unsigned long offset, unsigned long head)
        return 0;
 }
 
+static int
+process_lost_event(event_t *event, unsigned long offset, unsigned long head)
+{
+       dprintf("%p [%p]: PERF_EVENT_LOST: id:%Ld: lost:%Ld\n",
+               (void *)(offset + head),
+               (void *)(long)(event->header.size),
+               event->lost.id,
+               event->lost.lost);
+
+       total_lost += event->lost.lost;
+
+       return 0;
+}
+
 static void trace_event(event_t *event)
 {
        unsigned char *raw_event = (void *)event;
@@ -1316,6 +1338,10 @@ process_event(event_t *event, unsigned long offset, unsigned long head)
 
        case PERF_EVENT_PERIOD:
                return process_period_event(event, offset, head);
+
+       case PERF_EVENT_LOST:
+               return process_lost_event(event, offset, head);
+
        /*
         * We dont process them right now but they are fine:
         */
@@ -1444,6 +1470,7 @@ more:
        dprintf("    mmap events: %10ld\n", total_mmap);
        dprintf("    comm events: %10ld\n", total_comm);
        dprintf("    fork events: %10ld\n", total_fork);
+       dprintf("    lost events: %10ld\n", total_lost);
        dprintf(" unknown events: %10ld\n", total_unknown);
 
        if (dump_trace)