Re: [PATCHv3 2/2] perf tools: Fix tracing info recording

[Jiri Olsa]

hi,
any feedback on this?

I cut off changes colliding with Steven's change,
now it just fixies the pipe/file issue..

thanks,
jirka


On Thu, Sep 29, 2011 at 05:05:09PM +0200, Jiri Olsa wrote:
> Fixing the way the tracing information is stored within record command.
> The current implementation is causing issues for pipe output.
> 
> Following commands fail currently:
> 	perf script syscall-counts ls
> 	perf record -e syscalls:sys_exit_read ls | ./perf report -i -
> 
> The tracing information is part of the perf data file. It contains
> several files from within the tracing debugfs and procs directories.
> 
> Beside some static header files, for each tracing event the format
> file is added. The /proc/kallsyms file is also added.
> 
> The tracing data are stored with preceeding size. This is causing some
> dificulties for pipe output, since there's no way to tell debugfs/proc
> file size before reading it. So, for pipe output, all the debugfs files
> were read twice. Once to get the overall size and once to store the
> content itself. This can cause problem in case any of these file
> changed, within the storage time.
> 
> To fix this behaviour and ensure the integrity of the tracing data, we:
>     - read debugfs/proc file into the temp file
>     - get temp file size and dump it to the pipe
>     - dump the temp file contents to the pipe
> 
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
>  tools/perf/util/header.c           |   50 +++++++++++++++---
>  tools/perf/util/trace-event-info.c |  102 ++++++++++++++++++++++++++---------
>  tools/perf/util/trace-event.h      |   11 +++-
>  3 files changed, 127 insertions(+), 36 deletions(-)
> 
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index b6c1ad1..477c73b 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -382,18 +382,33 @@ static int perf_header__adds_write(struct perf_header *header,
>  
>  	sec_size = sizeof(*feat_sec) * nr_sections;
>  
> +	/*
> +	 * We reserve header space for each section, and
> +	 * update/store it later once we know the section size.
> +	 */
>  	sec_start = header->data_offset + header->data_size;
>  	lseek(fd, sec_start + sec_size, SEEK_SET);
>  
>  	if (perf_header__has_feat(header, HEADER_TRACE_INFO)) {
>  		struct perf_file_section *trace_sec;
> +		struct tracing_data *tdata;
>  
>  		trace_sec = &feat_sec[idx++];
> -
> -		/* Write trace info */
>  		trace_sec->offset = lseek(fd, 0, SEEK_CUR);
> -		read_tracing_data(fd, &evlist->entries);
> -		trace_sec->size = lseek(fd, 0, SEEK_CUR) - trace_sec->offset;
> +
> +		/*
> +		 * We work over the real file, so we can write data
> +		 * directly, no temp file is needed.
> +		 */
> +		tdata = tracing_data_get(&evlist->entries, fd, false);
> +		if (!tdata)
> +			goto out_free;
> +
> +		/*
> +		 * Update the section header information.
> +		 */
> +		trace_sec->size = tdata->size;
> +		tracing_data_put(tdata);
>  	}
>  
>  	if (perf_header__has_feat(header, HEADER_BUILD_ID)) {
> @@ -1100,15 +1115,29 @@ int perf_event__synthesize_tracing_data(int fd, struct perf_evlist *evlist,
>  				   struct perf_session *session __unused)
>  {
>  	union perf_event ev;
> +	struct tracing_data *tdata;
>  	ssize_t size = 0, aligned_size = 0, padding;
>  	int err __used = 0;
>  
> +	/*
> +	 * We are going to store the size of the data followed
> +	 * by the data contents. Since the fd descriptor is a pipe,
> +	 * we cannot seek back to store the size of the data once
> +	 * we know it. Instead we:
> +	 *
> +	 * - write the tracing data to the temp file
> +	 * - get/write the data size to pipe
> +	 * - write the tracing data from the temp file
> +	 *   to the pipe
> +	 */
> +	tdata = tracing_data_get(&evlist->entries, fd, true);
> +	if (!tdata)
> +		return -1;
> +
>  	memset(&ev, 0, sizeof(ev));
>  
>  	ev.tracing_data.header.type = PERF_RECORD_HEADER_TRACING_DATA;
> -	size = read_tracing_data_size(fd, &evlist->entries);
> -	if (size <= 0)
> -		return size;
> +	size = tdata->size;
>  	aligned_size = ALIGN(size, sizeof(u64));
>  	padding = aligned_size - size;
>  	ev.tracing_data.header.size = sizeof(ev.tracing_data);
> @@ -1116,7 +1145,12 @@ int perf_event__synthesize_tracing_data(int fd, struct perf_evlist *evlist,
>  
>  	process(&ev, NULL, session);
>  
> -	err = read_tracing_data(fd, &evlist->entries);
> +	/*
> +	 * The put function will copy all the tracing data
> +	 * stored in temp file to the pipe.
> +	 */
> +	tracing_data_put(tdata);
> +
>  	write_padded(fd, NULL, 0, padding);
>  
>  	return aligned_size;
> diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
> index 3403f81..c9aa4c9 100644
> --- a/tools/perf/util/trace-event-info.c
> +++ b/tools/perf/util/trace-event-info.c
> @@ -196,7 +196,8 @@ static void record_file(const char *file, size_t hdr_sz)
>  		die("Can't read '%s'", file);
>  
>  	/* put in zeros for file size, then fill true size later */
> -	write_or_die(&size, hdr_sz);
> +	if (hdr_sz)
> +		write_or_die(&size, hdr_sz);
>  
>  	do {
>  		r = read(fd, buf, BUFSIZ);
> @@ -212,7 +213,7 @@ static void record_file(const char *file, size_t hdr_sz)
>  	if (bigendian())
>  		sizep += sizeof(u64) - hdr_sz;
>  
> -	if (pwrite(output_fd, sizep, hdr_sz, hdr_pos) < 0)
> +	if (hdr_sz && pwrite(output_fd, sizep, hdr_sz, hdr_pos) < 0)
>  		die("writing to %s", output_file);
>  }
>  
> @@ -428,6 +429,19 @@ get_tracepoints_path(struct list_head *pattrs)
>  	return nr_tracepoints > 0 ? path.next : NULL;
>  }
>  
> +static void
> +put_tracepoints_path(struct tracepoint_path *tps)
> +{
> +	while (tps) {
> +		struct tracepoint_path *t = tps;
> +
> +		tps = tps->next;
> +		free(t->name);
> +		free(t->system);
> +		free(t);
> +	}
> +}
> +
>  bool have_tracepoints(struct list_head *pattrs)
>  {
>  	struct perf_evsel *pos;
> @@ -439,19 +453,11 @@ bool have_tracepoints(struct list_head *pattrs)
>  	return false;
>  }
>  
> -int read_tracing_data(int fd, struct list_head *pattrs)
> +static void tracing_data_header(void)
>  {
> -	char buf[BUFSIZ];
> -	struct tracepoint_path *tps = get_tracepoints_path(pattrs);
> -
> -	/*
> -	 * What? No tracepoints? No sense writing anything here, bail out.
> -	 */
> -	if (tps == NULL)
> -		return -1;
> -
> -	output_fd = fd;
> +	char buf[50];
>  
> +	/* just guessing this is someone's birthday.. ;) */
>  	buf[0] = 23;
>  	buf[1] = 8;
>  	buf[2] = 68;
> @@ -476,28 +482,72 @@ int read_tracing_data(int fd, struct list_head *pattrs)
>  	/* save page_size */
>  	page_size = sysconf(_SC_PAGESIZE);
>  	write_or_die(&page_size, 4);
> +}
> +
> +struct tracing_data *tracing_data_get(struct list_head *pattrs,
> +				      int fd, bool temp)
> +{
> +	struct tracepoint_path *tps;
> +	struct tracing_data *tdata;
> +
> +	output_fd = fd;
> +
> +	tps = get_tracepoints_path(pattrs);
> +	if (!tps)
> +		return NULL;
> +
> +	tdata = malloc_or_die(sizeof(*tdata));
> +	tdata->temp = temp;
> +	tdata->size = 0;
> +
> +	if (temp) {
> +		int temp_fd;
> +
> +		snprintf(tdata->temp_file, sizeof(tdata->temp_file),
> +			 "/tmp/perf-XXXXXX");
> +		if (!mkstemp(tdata->temp_file))
> +			die("Can't make temp file");
> +
> +		temp_fd = open(tdata->temp_file, O_RDWR);
> +		if (temp_fd < 0)
> +			die("Can't read '%s'", tdata->temp_file);
> +
> +		/*
> +		 * Set the temp file the default output, so all the
> +		 * tracing data are stored into it.
> +		 */
> +		output_fd = temp_fd;
> +	} else
> +		tdata->size = -lseek(output_fd, 0, SEEK_CUR);
>  
> +	tracing_data_header();
>  	read_header_files();
>  	read_ftrace_files(tps);
>  	read_event_files(tps);
>  	read_proc_kallsyms();
>  	read_ftrace_printk();
>  
> -	return 0;
> -}
> +	tdata->size += lseek(output_fd, 0, SEEK_CUR);
>  
> -ssize_t read_tracing_data_size(int fd, struct list_head *pattrs)
> -{
> -	ssize_t size;
> -	int err = 0;
> +	/*
> +	 * All tracing data are stored by now, we can restore
> +	 * the default output file in case we used temp file.
> +	 */
> +	if (temp) {
> +		close(output_fd);
> +		output_fd = fd;
> +	}
>  
> -	calc_data_size = 1;
> -	err = read_tracing_data(fd, pattrs);
> -	size = calc_data_size - 1;
> -	calc_data_size = 0;
> +	put_tracepoints_path(tps);
> +	return tdata;
> +}
>  
> -	if (err < 0)
> -		return err;
> +void tracing_data_put(struct tracing_data *tdata)
> +{
> +	if (tdata->temp) {
> +		record_file(tdata->temp_file, 0);
> +		unlink(tdata->temp_file);
> +	}
>  
> -	return size;
> +	free(tdata);
>  }
> diff --git a/tools/perf/util/trace-event.h b/tools/perf/util/trace-event.h
> index f674dda..92274b9 100644
> --- a/tools/perf/util/trace-event.h
> +++ b/tools/perf/util/trace-event.h
> @@ -262,8 +262,15 @@ raw_field_value(struct event *event, const char *name, void *data);
>  void *raw_field_ptr(struct event *event, const char *name, void *data);
>  unsigned long long eval_flag(const char *flag);
>  
> -int read_tracing_data(int fd, struct list_head *pattrs);
> -ssize_t read_tracing_data_size(int fd, struct list_head *pattrs);
> +struct tracing_data {
> +	ssize_t size;
> +	bool temp;
> +	char temp_file[50];
> +};
> +
> +struct tracing_data *tracing_data_get(struct list_head *pattrs,
> +				      int fd, bool temp);
> +void tracing_data_put(struct tracing_data *tdata);
>  
>  /* taken from kernel/trace/trace.h */
>  enum trace_flag_type {
> -- 
> 1.7.4
> 
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