linux-kernel - [PATCH v1 2/6] perf Documentation: Update perf.data-file-format.txt

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Date:   Wed, 20 Sep 2017 23:12:33 +0800
From:   Jin Yao <yao.jin@...ux.intel.com>
To:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com
Cc:     Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com,
        Jin Yao <yao.jin@...ux.intel.com>
Subject: [PATCH v1 2/6] perf Documentation: Update perf.data-file-format.txt

Currently the perf.data file starts with a perf_file_header,
while in the document, it's perf_header. So update it by the
new definition.

It also adds the description for new fields first_sample_time
and last_sample_time. The new fields will be used in perf
record/script/... to slice the traces.

Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
---
 tools/perf/Documentation/perf.data-file-format.txt | 27 +++++++++++++---------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/tools/perf/Documentation/perf.data-file-format.txt b/tools/perf/Documentation/perf.data-file-format.txt
index e90c59c..7c27403 100644
--- a/tools/perf/Documentation/perf.data-file-format.txt
+++ b/tools/perf/Documentation/perf.data-file-format.txt
@@ -14,17 +14,18 @@ format that does not rely on seeking to adjust data offsets.  This
 format is described in "Pipe-mode data" section. The pipe data version can be
 augmented with additional events using perf inject.
 
-The file starts with a perf_header:
-
-struct perf_header {
-	char magic[8];		/* PERFILE2 */
-	uint64_t size;		/* size of the header */
-	uint64_t attr_size;	/* size of an attribute in attrs */
-	struct perf_file_section attrs;
-	struct perf_file_section data;
-	struct perf_file_section event_types;
-	uint64_t flags;
-	uint64_t flags1[3];
+The file starts with a perf_file_header:
+
+struct perf_file_header {
+	u64				magic;
+	u64				size;
+	u64				attr_size;
+	struct perf_file_section	attrs;
+	struct perf_file_section	data;
+	struct perf_file_section	event_types;
+	DECLARE_BITMAP(adds_features, HEADER_FEAT_BITS);
+	u64				first_sample_time;
+	u64				last_sample_time;
 };
 
 The magic number identifies the perf file and the version. Current perf versions
@@ -416,6 +417,10 @@ An array bound by the perf_file_section size.
 
 ids points to a array of uint64_t defining the ids for event attr attr.
 
+first_sample_time and last_sample_time record the timestmaps of first sample
+and last sample. In later, perf record will fetch the time from perf file
+header and use them to slice the traces for parallelization.
+
 Pipe-mode data
 
 Pipe-mode avoid seeks in the file by removing the perf_file_section and flags
-- 
2.7.4