From: Kan Liang <kan.li...@intel.com> The latency of perf_top__mmap_read should be lower than refresh time. If not, give some hints to reduce the overhead.
Signed-off-by: Kan Liang <kan.li...@intel.com> --- tools/perf/builtin-top.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c index 03090d0..b5143c9 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -863,11 +863,20 @@ static void perf_top__mmap_read_idx(struct perf_top *top, int idx) static void perf_top__mmap_read(struct perf_top *top) { + unsigned long long s, e; int i; perf_evlist__toggle_bkw_mmap(top->evlist, BKW_MMAP_DATA_PENDING); + s = rdclock(); for (i = 0; i < top->evlist->nr_mmaps; i++) perf_top__mmap_read_idx(top, i); + e = rdclock(); + if ((e - s) > (unsigned long long)(top->delay_secs * NSEC_PER_SEC)) { + ui__warning("Too slow to read ring buffer.\n" + "Please try increasing the period (-c) or\n" + "decreasing the freq (-F) or\n" + "limiting the number of CPUs (-C)\n"); + } perf_evlist__toggle_bkw_mmap(top->evlist, BKW_MMAP_EMPTY); perf_evlist__toggle_bkw_mmap(top->evlist, BKW_MMAP_RUNNING); } -- 2.5.5