linux-kernel - Re: [PATCH 3/5] perf expr: Increase EXPR_MAX

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Date:   Mon, 24 Feb 2020 13:03:08 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        John Garry <john.garry@...wei.com>
Subject: Re: [PATCH 3/5] perf expr: Increase EXPR_MAX_OTHER

On Mon, Feb 24, 2020 at 09:29:16AM +0100, Jiri Olsa wrote:
> There's no need to be greedy on allowed variables, also
> when some of the metrics define more than 15 variables,
> like Branch_Misprediction_Cost.
> 
> Increasing the maximum to 100.

FWIW some of the algorithms (e.g. already_seen) have O(n^2) complexity.

If you really want that many probably would need to add some hash tables.

-Andi