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SubjectRe: [PATCH] perf: update perf.data file format documentation
On Fri, Feb 15, 2019 at 07:28:23PM +0100, Jonas Rabenstein wrote:
> I found that the documentation of the flags section is some how
> different from the actual format used and expected by the perf
> tools. In this patch the according section of the file format
> documentation is updated to conform to the expectations of the
> perf tool suite.
>
> Signed-off-by: Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>
> ---
> .../perf/Documentation/perf.data-file-format.txt | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf.data-file-format.txt b/tools/perf/Documentation/perf.data-file-format.txt
> index dfb218feaad9..6ea199f28330 100644
> --- a/tools/perf/Documentation/perf.data-file-format.txt
> +++ b/tools/perf/Documentation/perf.data-file-format.txt
> @@ -43,13 +43,10 @@ struct perf_file_section {
>
> Flags section:
>
> -The header is followed by different optional headers, described by the bits set
> -in flags. Only headers for which the bit is set are included. Each header
> -consists of a perf_file_section located after the initial header.
> -The respective perf_file_section points to the data of the additional
> -header and defines its size.
> -
> -Some headers consist of strings, which are defined like this:
> +The Flags section is placed directly after the data section and consists of a
> +variable amount of information described by the flags-bitset in the perf_header.
> +A lot of the headers in the Flags section are simple strings and are represented
> +like this:

some how I find this more confusing.. please describe
what's actualy wrong with the current wording

>
> struct perf_header_string {
> uint32_t len;
> @@ -82,7 +79,7 @@ assigned by the linker to an executable.
> struct build_id_event {
> struct perf_event_header header;
> pid_t pid;
> - uint8_t build_id[24];
> + uint8_t build_id[PERF_ALIGN(24, sizeof(u64))];

isn't that always 24? I guess u meant:

build_id[PERF_ALIGN(20, sizeof(u64))];


> char filename[header.size - offsetof(struct build_id_event, filename)];
> };
>
> @@ -131,7 +128,7 @@ An uint64_t with the total memory in bytes.
>
> HEADER_CMDLINE = 11,
>
> -A perf_header_string with the perf command line used to collect the data.
> +A perf_header_string_list with the perf arg-vector used to collect the data.

nice catch

thanks,
jirka

>
> HEADER_EVENT_DESC = 12,
>
> --
> 2.17.1
>

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