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Message-Id: <20240829150154.37929-6-irogers@google.com>
Date: Thu, 29 Aug 2024 08:01:51 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>, Nick Terrell <terrelln@...com>,
Yanteng Si <siyanteng@...ngson.cn>, Yicong Yang <yangyicong@...ilicon.com>,
James Clark <james.clark@...aro.org>, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v1 5/8] perf header: Allow attributes to be written after data
With a file, to write data an offset needs to be known. Typically data
follows the event attributes in a file. However, if processing a pipe
the number of event attributes may not be known. It is convenient in
that case to write the attributes after the data. Expand
perf_session__do_write_header to allow this when the data offset and
size are known.
This approach may be useful for more than just taking a pipe file to
write into a data file, `perf inject --itrace` will reserve and
additional 8kb for attributes, which would be unnecessary if the
attributes were written after the data.
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
tools/perf/util/header.c | 106 +++++++++++++++++++++++++--------------
1 file changed, 67 insertions(+), 39 deletions(-)
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 65c9086610cb..4eb39463067e 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3676,32 +3676,50 @@ int perf_header__write_pipe(int fd)
static int perf_session__do_write_header(struct perf_session *session,
struct evlist *evlist,
int fd, bool at_exit,
- struct feat_copier *fc)
+ struct feat_copier *fc,
+ bool write_attrs_after_data)
{
struct perf_file_header f_header;
- struct perf_file_attr f_attr;
struct perf_header *header = &session->header;
struct evsel *evsel;
struct feat_fd ff = {
.fd = fd,
};
- u64 attr_offset;
+ u64 attr_offset = sizeof(f_header), attr_size = 0;
int err;
- lseek(fd, sizeof(f_header), SEEK_SET);
+ if (write_attrs_after_data && at_exit) {
+ /*
+ * Write features at the end of the file first so that
+ * attributes may come after them.
+ */
+ if (!header->data_offset && header->data_size) {
+ pr_err("File contains data but offset unknown\n");
+ err = -1;
+ goto err_out;
+ }
+ header->feat_offset = header->data_offset + header->data_size;
+ err = perf_header__adds_write(header, evlist, fd, fc);
+ if (err < 0)
+ goto err_out;
+ attr_offset = lseek(fd, 0, SEEK_CUR);
+ } else {
+ lseek(fd, attr_offset, SEEK_SET);
+ }
evlist__for_each_entry(session->evlist, evsel) {
- evsel->id_offset = lseek(fd, 0, SEEK_CUR);
- err = do_write(&ff, evsel->core.id, evsel->core.ids * sizeof(u64));
- if (err < 0) {
- pr_debug("failed to write perf header\n");
- free(ff.buf);
- return err;
+ evsel->id_offset = attr_offset;
+ /* Avoid writing at the end of the file until the session is exiting. */
+ if (!write_attrs_after_data || at_exit) {
+ err = do_write(&ff, evsel->core.id, evsel->core.ids * sizeof(u64));
+ if (err < 0) {
+ pr_debug("failed to write perf header\n");
+ goto err_out;
+ }
}
+ attr_offset += evsel->core.ids * sizeof(u64);
}
- attr_offset = lseek(ff.fd, 0, SEEK_CUR);
-
evlist__for_each_entry(evlist, evsel) {
if (evsel->core.attr.size < sizeof(evsel->core.attr)) {
/*
@@ -3711,40 +3729,46 @@ static int perf_session__do_write_header(struct perf_session *session,
*/
evsel->core.attr.size = sizeof(evsel->core.attr);
}
- f_attr = (struct perf_file_attr){
- .attr = evsel->core.attr,
- .ids = {
- .offset = evsel->id_offset,
- .size = evsel->core.ids * sizeof(u64),
+ /* Avoid writing at the end of the file until the session is exiting. */
+ if (!write_attrs_after_data || at_exit) {
+ struct perf_file_attr f_attr = {
+ .attr = evsel->core.attr,
+ .ids = {
+ .offset = evsel->id_offset,
+ .size = evsel->core.ids * sizeof(u64),
+ }
+ };
+ err = do_write(&ff, &f_attr, sizeof(f_attr));
+ if (err < 0) {
+ pr_debug("failed to write perf header attribute\n");
+ goto err_out;
}
- };
- err = do_write(&ff, &f_attr, sizeof(f_attr));
- if (err < 0) {
- pr_debug("failed to write perf header attribute\n");
- free(ff.buf);
- return err;
}
+ attr_size += sizeof(struct perf_file_attr);
}
- if (!header->data_offset)
- header->data_offset = lseek(fd, 0, SEEK_CUR);
+ if (!header->data_offset) {
+ if (write_attrs_after_data)
+ header->data_offset = sizeof(f_header);
+ else
+ header->data_offset = attr_offset + attr_size;
+ }
header->feat_offset = header->data_offset + header->data_size;
- if (at_exit) {
+ if (!write_attrs_after_data && at_exit) {
+ /* Write features now feat_offset is known. */
err = perf_header__adds_write(header, evlist, fd, fc);
- if (err < 0) {
- free(ff.buf);
- return err;
- }
+ if (err < 0)
+ goto err_out;
}
f_header = (struct perf_file_header){
.magic = PERF_MAGIC,
.size = sizeof(f_header),
- .attr_size = sizeof(f_attr),
+ .attr_size = sizeof(struct perf_file_attr),
.attrs = {
.offset = attr_offset,
- .size = evlist->core.nr_entries * sizeof(f_attr),
+ .size = attr_size,
},
.data = {
.offset = header->data_offset,
@@ -3757,21 +3781,24 @@ static int perf_session__do_write_header(struct perf_session *session,
lseek(fd, 0, SEEK_SET);
err = do_write(&ff, &f_header, sizeof(f_header));
- free(ff.buf);
if (err < 0) {
pr_debug("failed to write perf header\n");
- return err;
+ goto err_out;
+ } else {
+ lseek(fd, 0, SEEK_END);
+ err = 0;
}
- lseek(fd, header->data_offset + header->data_size, SEEK_SET);
-
- return 0;
+err_out:
+ free(ff.buf);
+ return err;
}
int perf_session__write_header(struct perf_session *session,
struct evlist *evlist,
int fd, bool at_exit)
{
- return perf_session__do_write_header(session, evlist, fd, at_exit, NULL);
+ return perf_session__do_write_header(session, evlist, fd, at_exit, /*fc=*/NULL,
+ /*write_attrs_after_data=*/false);
}
size_t perf_session__data_offset(const struct evlist *evlist)
@@ -3793,7 +3820,8 @@ int perf_session__inject_header(struct perf_session *session,
int fd,
struct feat_copier *fc)
{
- return perf_session__do_write_header(session, evlist, fd, true, fc);
+ return perf_session__do_write_header(session, evlist, fd, true, fc,
+ /*write_attrs_after_data=*/false);
}
static int perf_header__getbuffer64(struct perf_header *header,
--
2.46.0.295.g3b9ea8a38a-goog
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