From: Kan Liang <[email protected]> The latency of perf_top__mmap_read should be lower than refresh time. If not, give some hints to reduce the latency.
Signed-off-by: Kan Liang <[email protected]> --- tools/perf/builtin-top.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c index 721d786..f36936c 100644 --- a/tools/perf/builtin-top.c +++ b/tools/perf/builtin-top.c @@ -872,13 +872,23 @@ 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 start, end; int i; + start = rdclock(); perf_evlist__toggle_bkw_mmap(top->evlist, BKW_MMAP_DATA_PENDING); for (i = 0; i < top->evlist->nr_mmaps; i++) perf_top__mmap_read_idx(top, i); perf_evlist__toggle_bkw_mmap(top->evlist, BKW_MMAP_EMPTY); perf_evlist__toggle_bkw_mmap(top->evlist, BKW_MMAP_RUNNING); + end = rdclock(); + + if ((end - start) > (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"); + } static int perf_top__start_counters(struct perf_top *top) -- 2.5.5
