From: Jiri Olsa <jolsa@redhat.com>
To: "Jin, Yao" <yao.jin@linux.intel.com>
Cc: acme@kernel.org, jolsa@kernel.org, peterz@infradead.org,
mingo@redhat.com, alexander.shishkin@linux.intel.com,
Linux-kernel@vger.kernel.org, ak@linux.intel.com,
kan.liang@intel.com, yao.jin@intel.com
Subject: Re: [PATCH v2 1/2] perf evlist: Ensure grouped events with same cpu map
Date: Wed, 27 May 2020 12:28:05 +0200 [thread overview]
Message-ID: <20200527102805.GA420698@krava> (raw)
In-Reply-To: <d6986a15-1e21-3414-9d68-c265e7db03f4@linux.intel.com>
On Wed, May 27, 2020 at 02:31:03PM +0800, Jin, Yao wrote:
SNIP
> > Thanks
> > Jin Yao
>
> Issue is found!
>
> It looks we can't set "pos->leader = pos" in either for_each_group_member()
> or in for_each_group_evsel() because it may exit the iteration immediately.
>
> evlist__for_each_entry(evlist, evsel) {
> if (evsel->leader == evsel)
> continue;
>
> if (cpu_maps_matched(evsel->leader, evsel))
> continue;
>
> pr_warning("WARNING: event cpu maps are not fully matched, "
> "disable group\n");
>
> for_each_group_member(pos, evsel->leader) {
> pos->leader = pos;
> pos->core.nr_members = 0;
> }
>
> Let me use the example of '{cycles,unc_cbo_cache_lookup.any_i}' again.
>
> In evlist:
> cycles,
> unc_cbo_cache_lookup.any_i,
> unc_cbo_cache_lookup.any_i,
> unc_cbo_cache_lookup.any_i,
> unc_cbo_cache_lookup.any_i,
>
> When we reach the for_each_group_member at first time, evsel is the first
> unc_cbo_cache_lookup.any_i and evsel->leader is cycles. pos is same as the
> evsel (the first unc_cbo_cache_lookup.any_i).
>
> Once we execute "pos->leader = pos;", it's actually "evsel->leader = evsel".
> So now evsel->leader is changed to the first unc_cbo_cache_lookup.any_i.
>
> In next iteration, pos is the second unc_cbo_cache_lookup.any_i. pos->leader
> is cycles but unfortunately evsel->leader has been changed to the first
> unc_cbo_cache_lookup.any_i. So iteration stops immediately.
hum, AFAICS the iteration will not break but continue to next evsel and
pass the 'continue' for another group member.. what do I miss?
jirka
>
> I'm now thinking if we can solve this issue by an easy way.
>
> Thanks
> Jin Yao
>
next prev parent reply other threads:[~2020-05-27 10:28 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-25 6:55 [PATCH v2 1/2] perf evlist: Ensure grouped events with same cpu map Jin Yao
2020-05-25 6:55 ` [PATCH v2 2/2] perf test: Add test case for group members Jin Yao
2020-05-26 11:51 ` [PATCH v2 1/2] perf evlist: Ensure grouped events with same cpu map Jiri Olsa
2020-05-27 3:20 ` Jin, Yao
2020-05-27 6:31 ` Jin, Yao
2020-05-27 7:26 ` Jin, Yao
2020-05-27 10:28 ` Jiri Olsa [this message]
2020-05-27 13:49 ` Jin, Yao
2020-05-27 16:28 ` Jiri Olsa
2020-05-28 1:47 ` Jin, Yao
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