linux-kernel - Re: [PATCH] perf jevents: Sort list of input files

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Message-ID: <ZBjdIbF7BDphCH+k@kernel.org>
Date:   Mon, 20 Mar 2023 19:24:33 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     "Bernhard M. Wiedemann" <bwiedemann@...e.de>
Cc:     Ian Rogers <irogers@...gle.com>, Ben Hutchings <benh@...ian.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf jevents: Sort list of input files

Em Mon, Mar 20, 2023 at 10:30:00PM +0100, Bernhard M. Wiedemann escreveu:
> 
> 
> On 20/03/2023 21.48, Ian Rogers wrote:
> > I think this may already be addressed by sorting prior to output:
> > https://lore.kernel.org/r/20220812230949.683239-5-irogers@google.com
> > 
> > Could you confirm?
> 
> Hi Ian,
> 
> I was testing on 6.2.6 which includes that patch and it was still affected.
> The trouble with sorting at the end is, that there can be influences of
> ordering in earlier processing steps, that don't get ironed out by the sort
> later.
> 
> Some more experimenting showed that only the ftw scandir needed sorting,
> which allows to further simplify the patch to
> 
>      """Replicate the directory/file walking behavior of C's ...
> -    for item in os.scandir(path):
> +    for item in sorted(os.scandir(path), key=lambda e: e.name):
>        action(parents, item)
> 
> 
> Without the patch, a random diff in pmu-events.c starts with
> -static const struct compact_pmu_event pme_amdzen2[] = {
> +static const struct compact_pmu_event pme_silvermont[] = {
> 
> 
> While I'm testing on scratch ext4 filesystems where dirindex causes
> randomness, you could also use the disorderfs FUSE-filesystem with its
> shuffle mode to give you random order.

So, Ian acked the current patch, but you found some further
simplification, can you please resubmit?

- Arnaldo