Messages in this thread | | | Subject | Re: [PATCH v5 07/10] perf record: implement -z,--compression_level=n option and compression | From | Alexey Budankov <> | Date | Thu, 7 Mar 2019 11:26:16 +0300 |
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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 (+=).
~Alexey
> > jirka >
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