linux-kernel - Re: [Cocci] Coccinelle: null: Optimise disjunctions in SmPL script “eno.cocci”

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Message-ID: <alpine.DEB.2.22.394.2010252122320.2714@hadrien>
Date:   Sun, 25 Oct 2020 21:27:27 +0100 (CET)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Markus Elfring <Markus.Elfring@....de>
cc:     Coccinelle <cocci@...teme.lip6.fr>,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Cocci] Coccinelle: null: Optimise disjunctions in SmPL script “eno.cocci”



On Sun, 25 Oct 2020, Markus Elfring wrote:

> >> Would you become interested to configure a representative test environment
> >> for safe comparisons of corresponding run time characteristics
> >> of the affected software?
> >
> > In what sense could the comparison possibly be unsafe?
>
> * Our test systems are obviously different.
>   Thus concerns can be considered for reproducibility of test results
>   on other possible configurations.
>
> * We share only a tiny fraction of technical information which would probably
>   be needed for “benchmarks”.
>
>
> > Just use time and run spatch on whatever machine you want.
>
> fring@...ne:~/Projekte/Linux/next-patched>
> elfring@...ne:~/Projekte/Linux/next-patched> git checkout next-20201023 && XX=$(date) && time spatch -D patch --timeout 9 --jobs 4 --chunksize 1 --include-headers --no-includes --dir . scripts/coccinelle/null/eno.cocci > ~/Projekte/Bau/Linux/scripts/Coccinelle/call_checks/20201023/eno1.diff 2> ~/Projekte/Bau/Linux/scripts/Coccinelle/call_checks/20201023/eno1-errors.txt; YY=$(date) && echo "$XX | $YY"
> …
> real	2m54,266s
> user	10m15,553s
> sys	0m4,004s
> So 25. Okt 20:53:56 CET 2020 | So 25. Okt 20:56:51 CET 2020
> elfring@...ne:~/Projekte/Linux/next-patched> git checkout next-20201023 && XX=$(date) && time spatch -D context --timeout 9 --jobs 4 --chunksize 1 --include-headers --no-includes --dir . scripts/coccinelle/null/eno.cocci > ~/Projekte/Bau/Linux/scripts/Coccinelle/call_checks/20201023/eno2.txt 2> ~/Projekte/Bau/Linux/scripts/Coccinelle/call_checks/20201023/eno2-errors.txt; YY=$(date) && echo "$XX | $YY"
> …
> real	2m38,494s
> user	9m39,364s
> sys	0m4,094s
> So 25. Okt 20:58:05 CET 2020 | So 25. Okt 21:00:44 CET 2020
> elfring@...ne:~/Projekte/Linux/next-patched> git checkout optimise_disjunction_in_eno.cocci-1 && XX=$(date) && time spatch -D patch --timeout 9 --jobs 4 --chunksize 1 --include-headers --no-includes --dir . scripts/coccinelle/null/eno.cocci > ~/Projekte/Bau/Linux/scripts/Coccinelle/call_checks/20201023/eno3.diff 2> ~/Projekte/Bau/Linux/scripts/Coccinelle/call_checks/20201023/eno3-errors.txt; YY=$(date) && echo "$XX | $YY"
> …
> real	2m46,097s
> user	10m15,467s
> sys	0m3,984s
> So 25. Okt 21:00:56 CET 2020 | So 25. Okt 21:03:42 CET 2020
> elfring@...ne:~/Projekte/Linux/next-patched> git checkout optimise_disjunction_in_eno.cocci-1 && XX=$(date) && time spatch -D context --timeout 9 --jobs 4 --chunksize 1 --include-headers --no-includes --dir . scripts/coccinelle/null/eno.cocci > ~/Projekte/Bau/Linux/scripts/Coccinelle/call_checks/20201023/eno4.txt 2> ~/Projekte/Bau/Linux/scripts/Coccinelle/call_checks/20201023/eno4-errors.txt; YY=$(date) && echo "$XX | $YY"
> …
> real	2m41,472s
> user	9m37,492s
> sys	0m3,834s

In the patch case, the user and system time are essentially identical.  In
the context case, the difference in user time is 2 seconds out of 9.5
minutes, 0.3%.

In the patch case, the real time is a bit slower.  But I believe that this
is due to the time to read in the data from the file system.  I also had a
number like that, but the difference disappeared when I reran it
afterwards, which meant running that case in the same conditions as the
others.

In the context case, the real time is slightly slower with your patch.

So I see no compelling evidence for making the change.

julia

> So 25. Okt 21:03:56 CET 2020 | So 25. Okt 21:06:37 CET 2020
>
>
> > Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz
>
> AMD Phenom(tm) II X4 850 Processor
>
> Will any other aspects become relevant?
>
> Regards,
> Markus
>