linux-kernel - Re: [PATCH] Speed up "make headers

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Date:	Sun, 8 Jun 2008 19:01:51 +0800
From:	WANG Cong <xiyou.wangcong@...il.com>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	Vegard Nossum <vegard.nossum@...il.com>,
	linux-kbuild <linux-kbuild@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jan Engelhardt <jengelh@...putergmbh.de>
Subject: Re: [PATCH] Speed up "make headers_*"

On Sun, Jun 08, 2008 at 12:41:22PM +0200, Sam Ravnborg wrote:
>On Sun, Jun 08, 2008 at 12:12:35PM +0200, Vegard Nossum wrote:
>> On Sun, Jun 8, 2008 at 11:47 AM, Sam Ravnborg <sam@...nborg.org> wrote:
>> > This is just a heads up patch if anyone is interested.
>> > I finally took the time needed to optimize the
>> > make headers_* targets.
>> >
>> > On my box it now takes less than 10 seconds to run
>> > the full install + check cycle.
>> > And it generates roughtly one screen full of output.
>> >
>> > Compare that to ~31 seconds and output filling up
>> > my scroll back buffer.
>> 
>> Nice :-)
>> 
>> > Comments (especially to the perl scripts) are welcome.
>> 
>> Will do! Some of my comments are a bit on the pedantic side, so you
>> choose yourself which ones you want to heed!
>
>Thnaks!
>
>headers_install.pl looks like this now.
>I am not happy about the way I call unifdef - can it be
>done better?
>No error handling and I like to avid the extra tmp file.


I think you can open a pipe in Perl, e.g. open FILE, "|scripts/unifdef";.


>
>	Sam
>
>#!/usr/bin/perl
>#
># headers_install prepare the listed header files for use in
># user space and copy the files to their destination.
>#
># Usage: headers_install.pl odir installdir [files...]
># odir:    dir to open files
># install: dir to install the files
># files:   list of files to check
>#
># Step in preparation for users space:
># 1) Drop all use of compiler.h definitions
># 2) Drop include of compiler.h
># 3) Drop all sections defined out by __KERNEL__
>
>use strict;
>use warnings;
>
>my ($odir, $installdir, @files) = @ARGV;
>
>my $ret = 0;


This is only used by last exit, thus can be removed.

>
>foreach my $file (@files) {
>	open(my $infile, '<', "$odir/$file") or die "$odir/$file: $!\n";
>	open(my $outfile, '>', "$installdir/$file.tmp") or
>		die "$installdir/$file.tmp: $!\n";
>	while (my $line = <$infile>) {
>		$line =~ s/([\s(])__user\s/$1/g;
>		$line =~ s/([\s(])__force\s/$1/g;
>		$line =~ s/([\s(])__iomem\s/$1/g;
>		$line =~ s/\s__attribute_const__\s/ /g;
>		$line =~ s/\s__attribute_const__$//g;
>		$line =~ s/^#include <linux\/compiler.h>//;
>		printf $outfile "%s", $line;
>	}
>	close($outfile);
>	close($outfile);


'close' doesn't need parenthesises neither.

>	system "scripts/unifdef -U__KERNEL__ $installdir/$file.tmp > $installdir/$file"


Will scripts/unifdef clean the tmp file? If not, you should do it, right?


>}
>
>exit $ret;
>


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