On 27.10.2020 15:01, Jiri Olsa wrote: > On Mon, Oct 26, 2020 at 05:11:30PM +0300, Alexei Budankov wrote: >> >> On 26.10.2020 13:34, Jiri Olsa wrote: >>> On Mon, Oct 26, 2020 at 11:21:28AM +0300, Alexei Budankov wrote: >>>> >>>> On 24.10.2020 18:43, Jiri Olsa wrote: >>>>> On Wed, Oct 21, 2020 at 07:07:00PM +0300, Alexey Budankov wrote: >>>>>> >>>>>> Introduce thread local variable and use it for threaded trace streaming. >>>>>> >>>>>> Signed-off-by: Alexey Budankov <[email protected]> >>>>>> --- >>>>>> tools/perf/builtin-record.c | 71 ++++++++++++++++++++++++++++++++----- >>>>>> 1 file changed, 62 insertions(+), 9 deletions(-) >>>>>> >>>>>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c >>>>>> index 89cb8e913fb3..3b7e9026f25b 100644 >>>>>> --- a/tools/perf/builtin-record.c >>>>>> +++ b/tools/perf/builtin-record.c >>>>>> @@ -101,6 +101,8 @@ struct thread_data { >>>>>> u64 bytes_written; >>>>>> }; >>>>>> >>>>>> +static __thread struct thread_data *thread; >>>>>> + >>>>>> struct record { >>>>>> struct perf_tool tool; >>>>>> struct record_opts opts; >>>>>> @@ -587,7 +589,11 @@ static int record__pushfn(struct mmap *map, void >>>>>> *to, void *bf, size_t size) >>>>>> } >>>>>> } >>>>>> >>>>>> - rec->samples++; >>>>>> + if (thread) >>>>>> + thread->samples++; >>>>>> + else >>>>>> + rec->samples++; >>>>> >>>>> this is really wrong, let's keep just single samples counter >>>>> ditto for all the other places in this patch >>>> >>>> This does look like data parallelism [1] which is very true for >>>> threaded trace streaming so your prototype design looks optimal. >>>> >>>> For this specific place incrementing global counter in memory is >>>> less performant and faces scalability limitations as a number of >>>> cores grow. >>>> >>>> Not sure why you have changed your mind. >>> >>> I'm not sure I follow.. what I'm complaining about is to have >>> 'samples' stat variable in separate locations for --threads >>> and --no-threads mode >> >> It is optimal to have samples variable as per thread one >> and then sum up the total in the end of data collection. >> >> Single global variable design has scalability and performance >> drawbacks. >> >> Why do you complain about per thread variable in this case? >> It looks like ideally fits these specific needs. > > I think there's misunderstanding.. I think we should move > samples to per thread 'thread' object and have just one > copy of that.. and do not increase separate variables for > thread and non-thread cases
Aw, I see. Using the same __thread object by main thread in serial and threaded modes. That makes sense. I will try in v3. Alexei > > jirka >
