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perf header: Allow attributes to be written after data

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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@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yanteng Si <siyanteng@loongson.cn>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20240829150154.37929-6-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2024-08-29 08:01:51 -07:00 committed by Arnaldo Carvalho de Melo
parent 10df481fda
commit e9a7053da3
1 changed files with 68 additions and 40 deletions
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84
tools/perf/util/header.c
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@ -3676,31 +3676,49 @@ 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);
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");
free(ff.buf);
return err;
goto err_out;
}
}
attr_offset = lseek(ff.fd, 0, SEEK_CUR);
attr_offset += evsel->core.ids * sizeof(u64);
}
evlist__for_each_entry(evlist, evsel) {
if (evsel->core.attr.size < sizeof(evsel->core.attr)) {
@ -3711,7 +3729,9 @@ 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){
/* 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,
@ -3721,30 +3741,34 @@ static int perf_session__do_write_header(struct perf_session *session,
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;
goto err_out;
}
}
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,