[PATCH 2/4] perf tools: Extract __perf_evlist__mmap_read()

From: Wang Nan
Date: Thu Apr 07 2016 - 05:43:27 EST


Extract event reader to __perf_evlist__mmap_read(). Future commit will
feed it with manually computed 'head' and 'old' pointers.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
tools/perf/util/evlist.c | 40 +++++++++++++++++++++++++---------------
1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 692fd05..119bf27 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -679,24 +679,15 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
return NULL;
}

-union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+static union perf_event *
+__perf_evlist__mmap_read(struct perf_mmap *md, bool overwrite, u64 head,
+ u64 old, u64 *prev)
{
- struct perf_mmap *md = &evlist->mmap[idx];
- u64 head;
- u64 old = md->prev;
- int diff;
unsigned char *data = md->base + page_size;
union perf_event *event = NULL;
+ int diff = head - old;

- /*
- * Check if event was unmapped due to a POLLHUP/POLLERR.
- */
- if (!atomic_read(&md->refcnt))
- return NULL;
-
- head = perf_mmap__read_head(md);
- diff = head - old;
- if (evlist->overwrite) {
+ if (overwrite) {
/*
* 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.
@@ -751,11 +742,30 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
}

broken_event:
- md->prev = old;
+ if (prev)
+ *prev = old;

return event;
}

+union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+{
+ struct perf_mmap *md = &evlist->mmap[idx];
+ u64 head;
+ u64 old = md->prev;
+
+ /*
+ * Check if event was unmapped due to a POLLHUP/POLLERR.
+ */
+ if (!atomic_read(&md->refcnt))
+ return NULL;
+
+ head = perf_mmap__read_head(md);
+
+ return __perf_evlist__mmap_read(md, evlist->overwrite, head,
+ old, &md->prev);
+}
+
static bool perf_mmap__empty(struct perf_mmap *md)
{
return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;
--
1.8.3.4