Em Sun, Sep 23, 2018 at 09:44:32PM +0200, Jiri Olsa escreveu: > On Mon, Sep 17, 2018 at 08:40:48PM +0900, Namhyung Kim wrote: > > On Thu, Sep 13, 2018 at 02:54:49PM +0200, Jiri Olsa wrote: > > > Currently we assign all maps to main thread. Adding > > > code that spreads maps for --threads option. > > > > > > For --thread option we create as many threads as there > > > are memory maps in evlist, which is the number of CPUs > > > in the system or CPUs we monitor. Each thread gets a > > > single data mmap to read. > > > > > > In addition we have also same amount of tracking mmaps > > > for auxiliary events which we don't create special thread > > > for. Instead we assign the to the main thread, because > > > there's not much traffic expected there. > > > > > > The assignment is visible from --thread-stats output: > > > > > > pid write poll skip maps (size 20K) > > > 1s 9770 144B 1 0 19K 19K 19K 18K > > > 19K > > > 9772 0B 1 0 18K > > > 9773 0B 1 0 19K > > > 9774 0B 1 0 19K > > > > > > There are 5 maps for thread 9770 (1 data map and 4 auxiliary) > > > and one data map for every other thread. Each thread writes > > > data to the separate data file. > > > > Hmm.. not sure it'll work well for large machines with 1000+ cpus. > > What about giving each thread a data mmap and a tracking mmap? > > well currently we store the tracking data in single file, > thats why we need just one thread to write them down
I agree with Namhyung, with a slight difference: perhaps we should set perf_event_attr.mmap on one of the events of the per-cpu mmap, that way we don't need that dummy event, right? > with the *_time API, we should be able to properly read the > tracking data separately for each cpu That may end up making the *_time API not needed (assuming the kernel keeps the per-cpu mmap events in order, barring that, using the ordered_events in batches, prior to consuming the events) and would help with things like 'perf top' and 'perf trace', that want to consume events right away. - Arnaldo
