Re: [RFC PATCH v2 1/2] perf tools: Set evsel->system_wide field for global system wide recording

From: Wangnan (F)
Date: Mon Oct 26 2015 - 23:24:22 EST

On 2015/10/26 21:02, Adrian Hunter wrote:
On 26/10/15 14:39, Wangnan (F) wrote:

On 2015/10/26 20:24, Adrian Hunter wrote:
On 26/10/15 13:41, Wang Nan wrote:
evsel->system_wide is introduced by commit bf8e8f4b832972c76d64ab2e2837
(perf evlist: Add 'system_wide' option), which is used for mixing evsels
that aren't system-wide with ones that are [1]. However, for global
system wide recording (perf record -a ...), evsel->system_wide is set
to false, which is confusion.

This patch set evsel->system_wide to true if the target.system_wide is
set, which makes evsel->system_wide a reliable way to describe whether
itself is system_wide or not.


Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
tools/perf/util/evsel.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 3ac4ee9c..36ecf0e 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -734,6 +734,7 @@ void perf_evsel__config(struct perf_evsel *evsel,
struct record_opts *opts)
int track = evsel->tracking;
bool per_cpu = opts->target.default_per_cpu &&
+ evsel->system_wide = opts->target.system_wide;
Well that breaks the way evsel->system_wide is used i.e. it is a parameter
to the evsel and here you just overwrote it.
Currently the only user of evsel->system_wide is IPT:

auxtrace_record__options -> intel_pt_recording_options

and it only set it to true.

So I think changing to this should make it safe:

evsel->system_wide = (evsel->system_wide || opt->target.system_wide);

That would work although it looks like a kludge.

Have you looked at properly validating opts->no_inherit ?

Also, aren't you neglecting target->cpu_list ?

I need this because Alexei's bpf_perf_event_output() helper needs perf side
support, and it only accept no-inherit perf event. I have already made a
patch[1] to support setting inherit bit per-event, so even without this and
next patch I can continue my work on bpf output. I'd like to rethink this
patch after I finish perf support for bpf output.

Thank you.


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