Re: [PATCH] perf data: Allow to use stdio functions for pipe mode
From: Ian Rogers
Date: Wed Oct 28 2020 - 18:15:41 EST
On Wed, Oct 28, 2020 at 1:56 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> When perf data is in a pipe, it reads each event separately using
> read(2) syscall. This is a huge performance bottleneck when
> processing large data like in perf inject. Also perf inject needs to
> use write(2) syscall for the output.
>
> So convert it to use buffer I/O functions in stdio library for pipe
> data. This makes inject-build-id bench time drops from 20ms to 8ms.
This is great! Reading the numbers below the times are reduced to
67.9% of their previous, this is a little less than 20ms to 8ms so
perhaps check that number.
> $ perf bench internals inject-build-id
> # Running 'internals/inject-build-id' benchmark:
> Average build-id injection took: 8.074 msec (+- 0.013 msec)
> Average time per event: 0.792 usec (+- 0.001 usec)
> Average memory usage: 8328 KB (+- 0 KB)
> Average build-id-all injection took: 5.490 msec (+- 0.008 msec)
> Average time per event: 0.538 usec (+- 0.001 usec)
> Average memory usage: 7563 KB (+- 0 KB)
>
> This patch enables it just for perf inject when used with pipe (it's a
> default behavior). Maybe we could do it for perf record and/or report
> later..
For perf record there is also the async IO used for writing. I like
that this patch is adding the reading to perf_data. Should the async
IO code live in perf_data rather than record? Should async IO be used
for reading in that case? What would be the policy of using stdio,
not-stdio and async IO?
Thanks,
Ian
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
> tools/perf/builtin-inject.c | 2 ++
> tools/perf/util/data.c | 36 +++++++++++++++++++++++++++++++++---
> tools/perf/util/data.h | 11 ++++++++++-
> tools/perf/util/header.c | 8 ++++----
> tools/perf/util/session.c | 7 ++++---
> 5 files changed, 53 insertions(+), 11 deletions(-)
>
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index 452a75fe68e5..14d6c88fed76 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -853,10 +853,12 @@ int cmd_inject(int argc, const char **argv)
> .output = {
> .path = "-",
> .mode = PERF_DATA_MODE_WRITE,
> + .use_stdio = true,
> },
> };
> struct perf_data data = {
> .mode = PERF_DATA_MODE_READ,
> + .use_stdio = true,
> };
> int ret;
>
> diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
> index c47aa34fdc0a..47b5a4b50ca5 100644
> --- a/tools/perf/util/data.c
> +++ b/tools/perf/util/data.c
> @@ -174,8 +174,16 @@ static bool check_pipe(struct perf_data *data)
> is_pipe = true;
> }
>
> - if (is_pipe)
> - data->file.fd = fd;
> + if (is_pipe) {
> + if (data->use_stdio) {
> + const char *mode;
> +
> + mode = perf_data__is_read(data) ? "r" : "w";
> + data->file.fptr = fdopen(fd, mode);
> + } else {
> + data->file.fd = fd;
> + }
> + }
>
> return data->is_pipe = is_pipe;
> }
> @@ -334,6 +342,9 @@ int perf_data__open(struct perf_data *data)
> if (check_pipe(data))
> return 0;
>
> + /* currently it allows stdio for pipe only */
> + data->use_stdio = false;
> +
> if (!data->path)
> data->path = "perf.data";
>
> @@ -353,7 +364,21 @@ void perf_data__close(struct perf_data *data)
> perf_data__close_dir(data);
>
> zfree(&data->file.path);
> - close(data->file.fd);
> +
> + if (data->use_stdio)
> + fclose(data->file.fptr);
> + else
> + close(data->file.fd);
> +}
> +
> +ssize_t perf_data__read(struct perf_data *data, void *buf, size_t size)
> +{
> + if (data->use_stdio) {
> + if (fread(buf, size, 1, data->file.fptr) == 1)
> + return size;
> + return feof(data->file.fptr) ? 0 : -1;
> + }
> + return readn(data->file.fd, buf, size);
> }
>
> ssize_t perf_data_file__write(struct perf_data_file *file,
> @@ -365,6 +390,11 @@ ssize_t perf_data_file__write(struct perf_data_file *file,
> ssize_t perf_data__write(struct perf_data *data,
> void *buf, size_t size)
> {
> + if (data->use_stdio) {
> + if (fwrite(buf, size, 1, data->file.fptr) == 1)
> + return size;
> + return -1;
> + }
> return perf_data_file__write(&data->file, buf, size);
> }
>
> diff --git a/tools/perf/util/data.h b/tools/perf/util/data.h
> index 75947ef6bc17..c563fcbb0288 100644
> --- a/tools/perf/util/data.h
> +++ b/tools/perf/util/data.h
> @@ -2,6 +2,7 @@
> #ifndef __PERF_DATA_H
> #define __PERF_DATA_H
>
> +#include <stdio.h>
> #include <stdbool.h>
>
> enum perf_data_mode {
> @@ -16,7 +17,10 @@ enum perf_dir_version {
>
> struct perf_data_file {
> char *path;
> - int fd;
> + union {
> + int fd;
> + FILE *fptr;
> + };
> unsigned long size;
> };
>
> @@ -26,6 +30,7 @@ struct perf_data {
> bool is_pipe;
> bool is_dir;
> bool force;
> + bool use_stdio;
> enum perf_data_mode mode;
>
> struct {
> @@ -62,11 +67,15 @@ static inline bool perf_data__is_single_file(struct perf_data *data)
>
> static inline int perf_data__fd(struct perf_data *data)
> {
> + if (data->use_stdio)
> + return fileno(data->file.fptr);
> +
> return data->file.fd;
> }
>
> int perf_data__open(struct perf_data *data);
> void perf_data__close(struct perf_data *data);
> +ssize_t perf_data__read(struct perf_data *data, void *buf, size_t size);
> ssize_t perf_data__write(struct perf_data *data,
> void *buf, size_t size);
> ssize_t perf_data_file__write(struct perf_data_file *file,
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index be850e9f8852..d9a70154426b 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -3652,7 +3652,8 @@ static int perf_file_section__process(struct perf_file_section *section,
> }
>
> static int perf_file_header__read_pipe(struct perf_pipe_file_header *header,
> - struct perf_header *ph, int fd,
> + struct perf_header *ph,
> + struct perf_data* data,
> bool repipe)
> {
> struct feat_fd ff = {
> @@ -3661,7 +3662,7 @@ static int perf_file_header__read_pipe(struct perf_pipe_file_header *header,
> };
> ssize_t ret;
>
> - ret = readn(fd, header, sizeof(*header));
> + ret = perf_data__read(data, header, sizeof(*header));
> if (ret <= 0)
> return -1;
>
> @@ -3684,8 +3685,7 @@ static int perf_header__read_pipe(struct perf_session *session)
> struct perf_header *header = &session->header;
> struct perf_pipe_file_header f_header;
>
> - if (perf_file_header__read_pipe(&f_header, header,
> - perf_data__fd(session->data),
> + if (perf_file_header__read_pipe(&f_header, header, session->data,
> session->repipe) < 0) {
> pr_debug("incompatible file format\n");
> return -EINVAL;
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 7a5f03764702..f901a09a58e4 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1923,7 +1923,6 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
> {
> struct ordered_events *oe = &session->ordered_events;
> struct perf_tool *tool = session->tool;
> - int fd = perf_data__fd(session->data);
> union perf_event *event;
> uint32_t size, cur_size = 0;
> void *buf = NULL;
> @@ -1943,7 +1942,8 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
> ordered_events__set_copy_on_queue(oe, true);
> more:
> event = buf;
> - err = readn(fd, event, sizeof(struct perf_event_header));
> + err = perf_data__read(session->data, event,
> + sizeof(struct perf_event_header));
> if (err <= 0) {
> if (err == 0)
> goto done;
> @@ -1975,7 +1975,8 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
> p += sizeof(struct perf_event_header);
>
> if (size - sizeof(struct perf_event_header)) {
> - err = readn(fd, p, size - sizeof(struct perf_event_header));
> + err = perf_data__read(session->data, p,
> + size - sizeof(struct perf_event_header));
> if (err <= 0) {
> if (err == 0) {
> pr_err("unexpected end of event stream\n");
> --
> 2.29.0.rc2.309.g374f81d7ae-goog
>