Re: [PATCH v5 07/10] perf record: implement -z,--compression_level=n option and compression

Jiri Olsa
2019-03-07T11:59:59Z

On Thu, Mar 07, 2019 at 11:26:16AM +0300, Alexey Budankov wrote:
>
> On 05.03.2019 15:26, Jiri Olsa wrote:
> > On Fri, Mar 01, 2019 at 06:58:32PM +0300, Alexey Budankov wrote:
> >
> > SNIP
> >
> >> +static size_t record__process_comp_header(void *record, size_t increment)
> >> +{
> >> + struct compressed_event *event = record;
> >> + size_t size = sizeof(struct compressed_event);
> >> +
> >> + if (increment) {
> >> + event->header.size += increment;
> >> + return increment;
> >> + } else {
> >> + event->header.type = PERF_RECORD_COMPRESSED;
> >> + event->header.size = size;
> >> + return size;
> >> + }
> >
> > so zstd_compress_stream_to_records calls this in the loop:
> >
> > while (input.pos < input.size) {
> > ...
> > size = process_header(record, 0);
> > ...
> > size = process_header(record, size);
> > }
> >
> > the header.size will get overwritten with every new iteration, no?
>
> Every new record is headed by PERF_RECORD_COMPRESSED header an updated with
> resulted compressed frame size after compression.
>
> process_header(, 0) puts header, then
> compression puts compressed frame, then
> process_header(, N) updates header.size value (+=).

and then process_header(, 0) is called again no?

jirka