linux-kernel - Re: [PATCH] Add a gfp-translate script to help understand page allocation failure reports

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Date:	Mon, 8 Jun 2009 09:59:06 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Rik van Riel <riel@...hat.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] Add a gfp-translate script to help understand page
	allocation failure reports

On Mon, Jun 08, 2009 at 02:29:50PM +0100, Mel Gorman wrote:
> The page allocation failure messages include a line that looks like
> 
> page allocation failure. order:1, mode:0x4020
> 
> The mode is easy to translate but irritating for the lazy and a bit error
> prone. This patch adds a very simple helper script gfp-translate for the mode:
> portion of the page allocation failure messages. An example usage looks like

Maybe we just just print the symbolic flags directly?  The even tracer
in the for-2.6.23 queue now has a __print_flags helper to translate the
bitmask back into symbolic flags, and we even have a kmalloc tracer
using it for the GFP flags.  Maybe we should add a printk_flags variant
for regular printks and just do the right thing?

> 
>   mel@...hina:~/linux-2.6 $ scripts/gfp-translate 0x4020
>   Source: /home/mel/linux-2.6
>   Parsing: 0x4020
>   #define __GFP_HIGH	(0x20)	/* Should access emergency pools? */
>   #define __GFP_COMP	(0x4000) /* Add compound page metadata */
> 
> The script is not a work of art but it has come in handy for me a few times
> so I thought I would share.
> 
> Signed-off-by: Mel Gorman <mel@....ul.ie>
> --- 
>  scripts/gfp-translate |   81 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 81 insertions(+)
> 
> diff --git a/scripts/gfp-translate b/scripts/gfp-translate
> new file mode 100755
> index 0000000..724db2d
> --- /dev/null
> +++ b/scripts/gfp-translate
> @@ -0,0 +1,81 @@
> +#!/bin/bash
> +# Translate the bits making up a GFP mask
> +# (c) 2009, Mel Gorman <mel@....ul.ie>
> +# Licensed under the terms of the GNU GPL License version 2
> +SOURCE=
> +GFPMASK=none
> +
> +# Helper function to report failures and exit
> +die() {
> +	echo ERROR: $@
> +	if [ "$TMPFILE" != "" ]; then
> +		rm -f $TMPFILE
> +	fi
> +	exit -1
> +}
> +
> +usage() {
> +	echo "usage: gfp-translate [-h] [ --source DIRECTORY ] gfpmask"
> +	exit 0
> +}
> +
> +# Parse command-line arguements
> +while [ $# -gt 0 ]; do
> +	case $1 in
> +		--source)
> +			SOURCE=$2
> +			shift 2
> +			;;
> +		-h)
> +			usage
> +			;;
> +		--help)
> +			usage
> +			;;
> +		*)
> +			GFPMASK=$1
> +			shift
> +			;;
> +	esac
> +done
> +
> +# Guess the kernel source directory if it's not set. Preference is in order of
> +# o current directory
> +# o /usr/src/linux
> +if [ "$SOURCE" = "" ]; then
> +	if [ -r "/usr/src/linux/Makefile" ]; then
> +		SOURCE=/usr/src/linux
> +	fi
> +	if [ -r "`pwd`/Makefile" ]; then
> +		SOURCE=`pwd`
> +	fi
> +fi
> +
> +# Confirm that a source directory exists
> +if [ ! -r "$SOURCE/Makefile" ]; then
> +	die "Could not locate source directory or it is invalid"
> +fi
> +
> +# Confirm that a GFP mask has been specified
> +if [ "$GFPMASK" = "none" ]; then
> +	usage
> +fi
> +
> +# Extract GFP flags from the kernel source
> +TMPFILE=`mktemp -t gfptranslate-XXXXXX` || exit 1
> +grep "^#define __GFP" $SOURCE/include/linux/gfp.h | sed -e 's/(__force gfp_t)//' | sed -e 's/u)/)/' | grep -v GFP_BITS | sed -e 's/)\//) \//' > $TMPFILE
> +
> +# Parse the flags
> +IFS="
> +"
> +echo Source: $SOURCE
> +echo Parsing: $GFPMASK
> +for LINE in `cat $TMPFILE`; do
> +	MASK=`echo $LINE | awk '{print $3}'`
> +	if [ $(($GFPMASK&$MASK)) -ne 0 ]; then
> +		echo $LINE
> +	fi
> +done
> +
> +rm -f $TMPFILE
> +exit 0
> --
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