Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: TuSkhEVgjw0jHxHBD9QScBk7J/rCtKt4ZkNIeig2YBvvrbY2mvWsTagCfPbh8bayvZkRcl+w7y
 YO1sUpswspVg==
IronPort-SDR: otJ5RVTFD0D3ZcvB0S2H/Pn/WnlUlu/sS3X9/nqs7F9fN59s0mjHnss6MGr3Lr04NP7idNs4CT
 xw3SG3Z12uaQ==
Date:   Fri, 8 May 2020 19:40:19 -0700
From:   Andi Kleen <ak@linux.intel.com>
To:     Ian Rogers <irogers@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        Kajol Jain <kjain@linux.ibm.com>,
        John Garry <john.garry@huawei.com>,
        Jin Yao <yao.jin@linux.intel.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        Kim Phillips <kim.phillips@amd.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        linux-perf-users <linux-perf-users@vger.kernel.org>,
        Vince Weaver <vincent.weaver@maine.edu>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [RFC PATCH v3 12/14] perf metricgroup: order event groups by size
Message-ID: <20200509024019.GI3538@tassilo.jf.intel.com>
References: <20200508053629.210324-1-irogers@google.com>
 <20200508053629.210324-13-irogers@google.com>
 <20200509002518.GF3538@tassilo.jf.intel.com>
 <CAP-5=fWYO2e9yVPuXGVKZ7TBP4PP6MjyEFiSd+20DOxYSLC--w@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAP-5=fWYO2e9yVPuXGVKZ7TBP4PP6MjyEFiSd+20DOxYSLC--w@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

> > 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