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Subject[PATCH 1/2] perf tools: Add reference timestamp to perf header
Date
Add a reference timestamp to the perf header - snapshotting kernel
time to gettimeofday. This allows 'perf report' to convert kernel
timestamps to time-of-day which is convenient for comparing to other
(non perf related) log files.

The timestamp is added using a feature bit for compatibility with
older binaries and data files.

Signed-off-by: David Ahern <daahern@cisco.com>
---
tools/perf/util/header.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/header.h | 3 ++
tools/perf/util/session.c | 26 +++++++++++++++++++++++
3 files changed, 80 insertions(+), 0 deletions(-)
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 76e949a..2fe893b 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -191,6 +191,40 @@ static int write_padded(int fd, const void *bf, size_t count,
return err;
}

+static int perf_header__read_ref_time(struct perf_header *header,
+ int fd, u64 offset, u64 size)
+{
+ size_t sz_nsec = sizeof(header->nsec_ref);
+ size_t sz_tv = sizeof(header->tv_ref);
+ int err = -1;
+
+ if (((size - offset) < (sz_nsec + sz_tv)) ||
+ (read(fd, &header->nsec_ref, sz_nsec) != (ssize_t) sz_nsec) ||
+ (read(fd, &header->tv_ref, sz_tv) != (ssize_t) sz_tv))
+ goto out;
+
+ err = 0;
+
+out:
+ return err;
+}
+
+static int perf_header__write_ref_time(struct perf_header *header, int fd)
+{
+ size_t sz_nsec = sizeof(header->nsec_ref);
+ size_t sz_tv = sizeof(header->tv_ref);
+ int err = -1;
+
+ if ((write(fd, &header->nsec_ref, sz_nsec) != (ssize_t) sz_nsec) ||
+ (write(fd, &header->tv_ref, sz_tv) != (ssize_t) sz_tv))
+ goto out;
+
+ err = 0;
+
+out:
+ return err;
+}
+
#define dsos__for_each_with_build_id(pos, head) \
list_for_each_entry(pos, head, node) \
if (!pos->has_build_id) \
@@ -483,6 +517,19 @@ static int perf_header__adds_write(struct perf_header *self, int fd)
perf_session__cache_build_ids(session);
}

+ if (perf_header__has_feat(self, HEADER_REFERENCE_TIME)) {
+ struct perf_file_section *tref_sec;
+
+ tref_sec = &feat_sec[idx++];
+ tref_sec->offset = lseek(fd, 0, SEEK_CUR);
+ err = perf_header__write_ref_time(self, fd);
+ if (err < 0) {
+ pr_debug("failed to write reference time\n");
+ goto out_free;
+ }
+ tref_sec->size = lseek(fd, 0, SEEK_CUR) - tref_sec->offset;
+ }
+
lseek(fd, sec_start, SEEK_SET);
err = do_write(fd, feat_sec, sec_size);
if (err < 0)
@@ -810,6 +857,10 @@ static int perf_file_section__process(struct perf_file_section *self,
if (perf_header__read_build_ids(ph, fd, self->offset, self->size))
pr_debug("Failed to read buildids, continuing...\n");
break;
+ case HEADER_REFERENCE_TIME:
+ if (perf_header__read_ref_time(ph, fd, self->offset, self->size))
+ pr_debug("Failed to read reference time, continuing...\n");
+ break;
default:
pr_debug("unknown feature %d, continuing...\n", feat);
}
diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
index 6335965..0721c78 100644
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -19,6 +19,7 @@ struct perf_header_attr {
enum {
HEADER_TRACE_INFO = 1,
HEADER_BUILD_ID,
+ HEADER_REFERENCE_TIME,
HEADER_LAST_FEATURE,
};

@@ -59,6 +60,8 @@ struct perf_header {
u64 data_size;
u64 event_offset;
u64 event_size;
+ u64 nsec_ref;
+ struct timeval tv_ref;
DECLARE_BITMAP(adds_features, HEADER_FEAT_BITS);
};

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 3074d38..720838e 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -110,6 +110,29 @@ void perf_session__update_sample_type(struct perf_session *self)
perf_session__id_header_size(self);
}

+static int perf_session__create_ref_time(struct perf_session *session)
+{
+ struct timespec tp;
+
+ /* race here between successive calls, but should be close enough */
+ if (gettimeofday(&session->header.tv_ref, NULL) != 0) {
+ pr_err("gettimeofday failed. Cannot set reference time.\n");
+ return -1;
+ }
+
+ if (clock_gettime(CLOCK_MONOTONIC, &tp) != 0) {
+ pr_err("clock_gettime failed. Cannot set reference time.\n");
+ return -1;
+ }
+
+ session->header.nsec_ref = (u64) tp.tv_sec * NSEC_PER_SEC
+ + (u64) tp.tv_nsec;
+
+ perf_header__set_feat(&session->header, HEADER_REFERENCE_TIME);
+
+ return 0;
+}
+
int perf_session__create_kernel_maps(struct perf_session *self)
{
int ret = machine__create_kernel_maps(&self->host_machine);
@@ -167,6 +190,9 @@ struct perf_session *perf_session__new(const char *filename, int mode, bool forc
*/
if (perf_session__create_kernel_maps(self) < 0)
goto out_delete;
+
+ if (perf_session__create_ref_time(self) < 0)
+ goto out_delete;
}

perf_session__update_sample_type(self);
--
1.7.2.3


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