From: Julia Lawall <julia.lawall@lip6.fr>
To: SF Markus Elfring <elfring@users.sourceforge.net>
Cc: Amitoj Kaur Chawla <amitoj1606@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Coccinelle <cocci@systeme.lip6.fr>,
Gilles Muller <Gilles.Muller@lip6.fr>,
Michal Marek <mmarek@suse.com>,
Nicolas Palix <nicolas.palix@imag.fr>
Subject: Re: [Cocci] [PATCH v3] Coccinelle: Script to replace allocate and memset with zalloc functions
Date: Mon, 1 Aug 2016 14:03:25 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.10.1608011359210.3188@hadrien> (raw)
In-Reply-To: <0dbd2dd6-4c68-1f7c-1500-9e5d40047813@users.sourceforge.net>
On Mon, 1 Aug 2016, SF Markus Elfring wrote:
> >> 1. Would it make sense to merge such SmPL rules into one
> >> so that code duplication could be reduced a bit
> >> in such a script?
> >
> > I think it would suffer in readability.
>
> How do you think about the following SmPL script example?
>
> @vz_combined
> depends on patch && !context && !org && !report@
> type T;
> T* pointer;
> +statement S;
> expression express;
> @@
> pointer =
> - vmalloc
> + vzalloc
> (...);
> if (!d)
> S
> -memset(d, 0, sizeof(
> (
> -T
> |
> -*(express)
> )
> -));
OK, I thought you meant to make a big disjunctions for all of the before
and after functions. This is a little better because it is bounded in
size. But I don't understand why you have introduced the variable
express. Normally one wants the cleared space to be the allocated size,
which is normally the size of *pointer.
The performance issue is that disjunctions on expressions, eg (A | B), are
implemented as (A | (!A & B)), ie with a negation of all the previous
options &d with each option. So it is better to avoid very large
disjunctions on expressions.
julia
>
>
> > Perhaps in performance as well.
>
> I admit that I am unsure about the run-time characteristics
> for my suggestion.
>
> Regards,
> Markus
>
WARNING: multiple messages have this Message-ID (diff)
From: julia.lawall@lip6.fr (Julia Lawall)
To: cocci@systeme.lip6.fr
Subject: [Cocci] [PATCH v3] Coccinelle: Script to replace allocate and memset with zalloc functions
Date: Mon, 1 Aug 2016 14:03:25 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.10.1608011359210.3188@hadrien> (raw)
In-Reply-To: <0dbd2dd6-4c68-1f7c-1500-9e5d40047813@users.sourceforge.net>
On Mon, 1 Aug 2016, SF Markus Elfring wrote:
> >> 1. Would it make sense to merge such SmPL rules into one
> >> so that code duplication could be reduced a bit
> >> in such a script?
> >
> > I think it would suffer in readability.
>
> How do you think about the following SmPL script example?
>
> @vz_combined
> depends on patch && !context && !org && !report@
> type T;
> T* pointer;
> +statement S;
> expression express;
> @@
> pointer =
> - vmalloc
> + vzalloc
> (...);
> if (!d)
> S
> -memset(d, 0, sizeof(
> (
> -T
> |
> -*(express)
> )
> -));
OK, I thought you meant to make a big disjunctions for all of the before
and after functions. This is a little better because it is bounded in
size. But I don't understand why you have introduced the variable
express. Normally one wants the cleared space to be the allocated size,
which is normally the size of *pointer.
The performance issue is that disjunctions on expressions, eg (A | B), are
implemented as (A | (!A & B)), ie with a negation of all the previous
options &d with each option. So it is better to avoid very large
disjunctions on expressions.
julia
>
>
> > Perhaps in performance as well.
>
> I admit that I am unsure about the run-time characteristics
> for my suggestion.
>
> Regards,
> Markus
>
next prev parent reply other threads:[~2016-08-01 12:03 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-01 7:02 [PATCH v3] Coccinelle: Script to replace allocate and memset with zalloc functions Amitoj Kaur Chawla
2016-08-01 7:02 ` [Cocci] " Amitoj Kaur Chawla
2016-08-01 11:23 ` SF Markus Elfring
2016-08-01 11:23 ` SF Markus Elfring
2016-08-01 11:37 ` Julia Lawall
2016-08-01 11:37 ` Julia Lawall
2016-08-01 11:56 ` SF Markus Elfring
2016-08-01 11:56 ` SF Markus Elfring
2016-08-01 12:03 ` Julia Lawall [this message]
2016-08-01 12:03 ` Julia Lawall
2016-08-01 12:24 ` SF Markus Elfring
2016-08-01 12:24 ` SF Markus Elfring
2016-08-01 12:32 ` Julia Lawall
2016-08-01 12:32 ` Julia Lawall
2016-08-01 12:45 ` SF Markus Elfring
2016-08-01 12:45 ` SF Markus Elfring
2016-08-19 12:14 ` Amitoj Kaur Chawla
2016-08-19 12:14 ` Amitoj Kaur Chawla
2016-08-19 12:41 ` Julia Lawall
2016-08-19 12:41 ` Julia Lawall
2016-08-19 13:26 ` [Cocci] " SF Markus Elfring
2016-08-19 13:26 ` SF Markus Elfring
2016-08-19 13:30 ` Julia Lawall
2016-08-19 13:30 ` Julia Lawall
2016-08-19 16:56 ` SF Markus Elfring
2016-08-19 16:56 ` SF Markus Elfring
2017-03-03 10:34 ` [Cocci] [PATCH v3] " SF Markus Elfring
2017-03-03 10:34 ` SF Markus Elfring
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