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Date: Fri, 8 May 2020 19:40:19 -0700 From: Andi Kleen <ak@...ux.intel.com> To: Ian Rogers <irogers@...gle.com> Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, Kajol Jain <kjain@...ux.ibm.com>, John Garry <john.garry@...wei.com>, Jin Yao <yao.jin@...ux.intel.com>, Kan Liang <kan.liang@...ux.intel.com>, Cong Wang <xiyou.wangcong@...il.com>, Kim Phillips <kim.phillips@....com>, LKML <linux-kernel@...r.kernel.org>, Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, linux-perf-users <linux-perf-users@...r.kernel.org>, Vince Weaver <vincent.weaver@...ne.edu>, Stephane Eranian <eranian@...gle.com> Subject: Re: [RFC PATCH v3 12/14] perf metricgroup: order event groups by size > > I'm not sure if size is that great an heuristic. The dedup algorithm should > > work in any case even if you don't order by size, right? > > Consider two metrics: > - metric 1 with events {A,B} > - metric 2 with events {A,B,C,D} > If the list isn't sorted then as the matching takes the first group > with all the events, metric 1 will match {A,B} and metric 2 {A,B,C,D}. > If the order is sorted to {A,B,C,D},{A,B} then metric 1 matches within > the {A,B,C,D} group as does metric 2. The events in metric 1 aren't > used and are removed. Ok. It's better for the longer metric if they stay together. > > The dedup algorithm is very naive :-) I guess what matters is that it gives reasonable results on the current metrics. I assume it does? How much deduping is happening if you run all metrics? For toplev on my long term todo list was to compare it against a hopefully better schedule generated by or-tools, but I never got around to coding that up. -Andi
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