On Fri, Dec 26, 2014 at 7:09 AM, Jiri Olsa <jo...@redhat.com> wrote: > On Wed, Dec 24, 2014 at 04:15:01PM +0900, Namhyung Kim wrote: > > SNIP > >> >> union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int >> idx); >> - >> void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx); >> +struct perf_mmap *perf_evlist__mmap_desc(struct perf_evlist *evlist, int >> idx); >> >> int perf_evlist__open(struct perf_evlist *evlist); >> void perf_evlist__close(struct perf_evlist *evlist); >> @@ -211,6 +214,12 @@ bool perf_evlist__can_select_event(struct perf_evlist >> *evlist, const char *str); >> void perf_evlist__to_front(struct perf_evlist *evlist, >> struct perf_evsel *move_evsel); >> >> +/* convert from/to negative idx for track mmaps */ >> +static inline int track_mmap_idx(int idx) >> +{ >> + return -idx - 1; >> +} > > hum, whats the logic with negative numbers in here? > you still access track_mmap array with this index no?
For each index (per-cpu or per-task depends on user input), it now has two mmaps - one for normal (sampling) mmap and another for track (metadata) mmap. So I wanted to distinguish them by using positive and negative number. But simply changing the sign did not work due to 0 index. And the subtracting by 1 works nicely for both direction. 0 => -1 => 0 1 => -2 => 1 2 => -3 => 2 3 => -4 => 3 So when it sees a negative index, it'll convert it using track_mmap_idx() to get a matching (track) mmap. Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/