Commit e9a7053d authored by Ian Rogers's avatar Ian Rogers Committed by Arnaldo Carvalho de Melo
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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: default avatarIan 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 10df481f

tools/perf/util/header.c

+67 −39
Original line number Diff line number Diff line
@@ -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,