perf evlist: Support non overwrite mode in perf_evlist__read_on_cpu
I.e. stash the overwrite mode in struct perf_evlist and act accordingly
in perf_evlist__read_on_cpu, not checking for overwrites and touching
the tail after consuming one event, like perf record does, for instance.
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 df0610e..b498eec 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -116,24 +116,25 @@
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");
-
+ if (evlist->overwrite) {
/*
- * head points to a known good entry, start there.
+ * 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.
*/
- old = head;
+ int 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) {
@@ -166,5 +167,9 @@
}
md->prev = old;
+
+ if (!evlist->overwrite)
+ perf_mmap__write_tail(md, old);
+
return event;
}
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index acbe48e..2706ae4 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -16,6 +16,7 @@
int nr_entries;
int nr_fds;
int mmap_len;
+ bool overwrite;
event_t event_copy;
struct perf_mmap *mmap;
struct pollfd *pollfd;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 76ab553..f98b3e5 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -327,6 +327,7 @@
perf_evlist__alloc_pollfd(evlist, cpus->nr, threads->nr) < 0)
return -ENOMEM;
+ evlist->overwrite = overwrite;
evlist->mmap_len = (pages + 1) * page_size;
first_evsel = list_entry(evlist->entries.next, struct perf_evsel, node);
