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Subject[tip:perf/urgent] perf mmap: Introduce perf_mmap__read_init()
Commit-ID:  701b3ef37c0a4a5168bc07cfd48b35727b5a922c
Gitweb: https://git.kernel.org/tip/701b3ef37c0a4a5168bc07cfd48b35727b5a922c
Author: Kan Liang <kan.liang@intel.com>
AuthorDate: Thu, 18 Jan 2018 13:26:19 -0800
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 6 Feb 2018 10:11:49 -0300

perf mmap: Introduce perf_mmap__read_init()

The new function perf_mmap__read_init() is factored out from
perf_mmap__push().

It is to calculate the 'start' and 'end' of the available data in
ringbuffer.

No functional change.

Signed-off-by: Kan Liang <kan.liang@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1516310792-208685-5-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/mmap.c | 37 +++++++++++++++++++++++++++----------
tools/perf/util/mmap.h | 2 ++
2 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index fbbbe87..c19a4e6 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -267,24 +267,24 @@ static int overwrite_rb_find_range(void *buf, int mask, u64 head, u64 *start, u6
return -1;
}

-int perf_mmap__push(struct perf_mmap *md, bool overwrite,
- void *to, int push(void *to, void *buf, size_t size))
+/*
+ * Report the start and end of the available data in ringbuffer
+ */
+int perf_mmap__read_init(struct perf_mmap *md, bool overwrite,
+ u64 *startp, u64 *endp)
{
u64 head = perf_mmap__read_head(md);
u64 old = md->prev;
- u64 end, start;
unsigned char *data = md->base + page_size;
unsigned long size;
- void *buf;
- int rc = 0;

- start = overwrite ? head : old;
- end = overwrite ? old : head;
+ *startp = overwrite ? head : old;
+ *endp = overwrite ? old : head;

- if (start == end)
+ if (*startp == *endp)
return 0;

- size = end - start;
+ size = *endp - *startp;
if (size > (unsigned long)(md->mask) + 1) {
if (!overwrite) {
WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
@@ -298,10 +298,27 @@ int perf_mmap__push(struct perf_mmap *md, bool overwrite,
* Backward ring buffer is full. We still have a chance to read
* most of data from it.
*/
- if (overwrite_rb_find_range(data, md->mask, head, &start, &end))
+ if (overwrite_rb_find_range(data, md->mask, head, startp, endp))
return -1;
}

+ return 1;
+}
+
+int perf_mmap__push(struct perf_mmap *md, bool overwrite,
+ void *to, int push(void *to, void *buf, size_t size))
+{
+ u64 head = perf_mmap__read_head(md);
+ u64 end, start;
+ unsigned char *data = md->base + page_size;
+ unsigned long size;
+ void *buf;
+ int rc = 0;
+
+ rc = perf_mmap__read_init(md, overwrite, &start, &end);
+ if (rc < 1)
+ return rc;
+
size = end - start;

if ((start & md->mask) + size != (end & md->mask)) {
diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
index e43d7b5..9ab2b48 100644
--- a/tools/perf/util/mmap.h
+++ b/tools/perf/util/mmap.h
@@ -94,4 +94,6 @@ int perf_mmap__push(struct perf_mmap *md, bool backward,

size_t perf_mmap__mmap_len(struct perf_mmap *map);

+int perf_mmap__read_init(struct perf_mmap *md, bool overwrite,
+ u64 *startp, u64 *endp);
#endif /*__PERF_MMAP_H */
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