linux-kernel - Re: [PATCH] perf stat: Take cgroups into account for shadow stats

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Date:   Sun, 15 Nov 2020 05:05:24 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH] perf stat: Take cgroups into account for shadow stats

> @@ -57,6 +59,9 @@ static int saved_value_cmp(struct rb_node *rb_node, const void *entry)
>  	if (a->ctx != b->ctx)
>  		return a->ctx - b->ctx;
>  
> +	if (a->cgrp != b->cgrp)
> +		return (char *)a->cgrp < (char *)b->cgrp ? -1 : +1;

This means the sort order will depend on heap randomization, 
which will make it harder to debug.

Better use something stable like the inode number of the cgroup.

Do we have the same problem with other filters?

The rest of the patch looks good to me.

-Andi