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

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Message-ID: <20090608132950.GB15070@csn.ul.ie>
Date:	Mon, 8 Jun 2009 14:29:50 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Rik van Riel <riel@...hat.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: [PATCH] Add a gfp-translate script to help understand page
	allocation failure reports

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

  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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