On Mon, Mar 1, 2021 at 10:33 PM Bayduraev, Alexey V <alexey.v.baydur...@linux.intel.com> wrote: > > 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?
It's only user space changes but it can be large. Actually I worked on parallelizing perf report several years ago (not finished, but I don't have time for it now). At the time, perf record didn't support directory output so I made it have indexes to different data parts. But you can get the idea from the code in https://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git/log/?h=perf/threaded-v5 Thanks, Namhyung
