perf evlist: Steal mmap reading routine from 'perf top'
Will be used in the upcoming 'perf test' entry for the evlist mmap
routines.
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index deb82a4..4b3b84c 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -95,3 +95,65 @@
return sid->evsel;
return NULL;
}
+
+event_t *perf_evlist__read_on_cpu(struct perf_evlist *evlist, int cpu)
+{
+ /* XXX Move this to perf.c, making it generally available */
+ unsigned int page_size = sysconf(_SC_PAGE_SIZE);
+ struct perf_mmap *md = &evlist->mmap[cpu];
+ unsigned int head = perf_mmap__read_head(md);
+ unsigned int old = md->prev;
+ unsigned char *data = md->base + page_size;
+ event_t *event = NULL;
+ int diff;
+
+ /*
+ * If we're further behind than half the buffer, there's a chance
+ * the writer will bite our tail and mess up the samples under us.
+ *
+ * If we somehow ended up ahead of the head, we got messed up.
+ *
+ * In either case, truncate and restart at head.
+ */
+ diff = head - old;
+ if (diff > md->mask / 2 || diff < 0) {
+ fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
+
+ /*
+ * head points to a known good entry, start there.
+ */
+ old = head;
+ }
+
+ if (old != head) {
+ size_t size;
+
+ event = (event_t *)&data[old & md->mask];
+ size = event->header.size;
+
+ /*
+ * Event straddles the mmap boundary -- header should always
+ * be inside due to u64 alignment of output.
+ */
+ if ((old & md->mask) + size != ((old + size) & md->mask)) {
+ unsigned int offset = old;
+ unsigned int len = min(sizeof(*event), size), cpy;
+ void *dst = &evlist->event_copy;
+
+ do {
+ cpy = min(md->mask + 1 - (offset & md->mask), len);
+ memcpy(dst, &data[offset & md->mask], cpy);
+ offset += cpy;
+ dst += cpy;
+ len -= cpy;
+ } while (len);
+
+ event = &evlist->event_copy;
+ }
+
+ old += size;
+ }
+
+ md->prev = old;
+ return event;
+}