On 01.03.2021 14:44, Namhyung Kim wrote: > Hello, > > On Mon, Mar 1, 2021 at 8:16 PM Bayduraev, Alexey V > <alexey.v.baydur...@linux.intel.com> wrote: >> >> Hi, >> >> On 20.11.2020 13:49, Namhyung Kim wrote: >>> On Mon, Nov 16, 2020 at 03:19:41PM +0300, Alexey Budankov wrote: >> >> <SNIP> >> >>>> >>>> @@ -1400,8 +1417,12 @@ static int record__mmap_read_evlist(struct record >>>> *rec, struct evlist *evlist, >>>> /* >>>> * Mark the round finished in case we wrote >>>> * at least one event. >>>> + * >>>> + * No need for round events in directory mode, >>>> + * because per-cpu maps and files have data >>>> + * sorted by kernel. >>> >>> But it's not just for single cpu since task can migrate so we need to >>> look at other cpu's data too. Thus we use the ordered events queue >>> and round events help to determine when to flush the data. Without >>> the round events, it'd consume huge amount of memory during report. >>> >>> If we separate tracking records and process them first, we should be >>> able to process samples immediately without sorting them in the >>> ordered event queue. This will save both cpu cycles and memory >>> footprint significantly IMHO. >>> >>> Thanks, >>> Namhyung >>> >> >> As far as I understand, to split tracing records (FORK/MMAP/COMM) into >> a separate file, we need to implement a runtime trace decoder on the >> perf-record side to recognize such tracing records coming from the kernel. >> Is that what you mean? > > No, I meant separating the mmap buffers so that the record process > can save the data without decoding. >
Thanks, Do you think this can be implemented only on the user side by creating a dummy event and manipulating by mmap/comm/task flags of struct perf_event_attr? Or some changes on the kernel side are necessary? Regards, Alexey >> >> IMHO this can be tricky to implement and adds some overhead that can lead >> to possible data loss. Do you have any other ideas how to optimize memory >> consumption on perf-report side without a runtime trace decoder? >> Maybe "round events" would somehow help in directory mode? >> >> BTW In our tool we use another approach: two-pass trace file loading. >> The first loads tracing records, the second loads samples. > > Yeah, something like that. With the separated data, we can do it > more efficiently IMHO. > > Thanks, > Namhyung >
