From: Dmitry Vyukov Date: Wed, 15 Jan 2025 08:00:42 +0000 (+0100) Subject: perf hist: Fix bogus profiles when filters are enabled X-Git-Tag: v6.14-rc1~120^2~8 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8b4799e4f0f40a4ec737bf870aa38d06288bf0fb;p=thirdparty%2Flinux.git perf hist: Fix bogus profiles when filters are enabled When a filtered column is not present in the sort order, profiles become arbitrary broken. Filtered and non-filtered entries are collapsed together, and the filtered-by field ends up with a random value (either from a filtered or non-filtered entry). If we end up with filtered entry/value, then the whole collapsed entry will be filtered out and will be missing in the profile. If we end up with non-filtered entry/value, then the overhead value will be wrongly larger (include some subset of filtered out samples). This leads to very confusing profiles. The problem is hard to notice, and if noticed hard to understand. If the filter is for a single value, then it can be fixed by adding the corresponding field to the sort order (provided user understood the problem). But if the filter is for multiple values, it's impossible to fix b/c there is no concept of binary sorting based on filter predicate (we want to group all non-filtered values in one bucket, and all filtered values in another). Examples of affected commands: perf report --tid=123 perf report --sort overhead,symbol --comm=foo,bar Fix this by considering filtered status as the highest priority sort/collapse predicate. As a side effect this effectively adds a new feature of showing profile where several lines are combined based on arbitrary filtering predicate. For example, showing symbols from binaries foo and bar combined together, but not from other binaries; or showing combined overhead of several particular threads. Signed-off-by: Dmitry Vyukov Link: https://lore.kernel.org/r/359dc444ce94d20e59d3a9e360c36fbeac833a04.1736927981.git.dvyukov@google.com Signed-off-by: Namhyung Kim --- diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c index 493b3cc30eac0..0f30f843c566d 100644 --- a/tools/perf/util/hist.c +++ b/tools/perf/util/hist.c @@ -1303,7 +1303,16 @@ hist_entry__cmp_impl(struct perf_hpp_list *hpp_list, struct hist_entry *left, struct hists *hists = left->hists; struct perf_hpp_fmt *fmt; perf_hpp_fmt_cmp_t *fn; - int64_t cmp = 0; + int64_t cmp; + + /* + * Never collapse filtered and non-filtered entries. + * Note this is not the same as having an extra (invisible) fmt + * that corresponds to the filtered status. + */ + cmp = (int64_t)!!left->filtered - (int64_t)!!right->filtered; + if (cmp) + return cmp; perf_hpp_list__for_each_sort_list(hpp_list, fmt) { if (ignore_dynamic && perf_hpp__is_dynamic_entry(fmt) &&