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Date: Thu, 19 Mar 2009 14:37:59 -0400 (EDT)
From: Christoph Lameter <cl@...ux-foundation.org>
To: Mel Gorman <mel@....ul.ie>
cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Linux Memory Management List <linux-mm@...ck.org>,
Pekka Enberg <penberg@...helsinki.fi>,
Rik van Riel <riel@...hat.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Johannes Weiner <hannes@...xchg.org>,
Nick Piggin <npiggin@...e.de>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Lin Ming <ming.m.lin@...el.com>,
Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 24/27] Convert gfp_zone() to use a table of precalculated
values
Some macros can get us around the problems:
Subject: Use a table lookup for gfp_zone and check for errors in flags passed to the page allocator
Use a table to lookup the zone to use given gfp_flags using gfp_zone().
This simplifies the code in gfp_zone() and also keeps the ability of the compiler to
use constant folding to get rid of gfp_zone processing.
We are doing some macro tricks here to convince the compiler to always do the
constant folding if possible.
Signed-off-by: Christoph Lameter <cl@...ux-foundation.org>
Index: linux-2.6/include/linux/gfp.h
===================================================================
--- linux-2.6.orig/include/linux/gfp.h 2009-03-19 11:43:32.000000000 -0500
+++ linux-2.6/include/linux/gfp.h 2009-03-19 13:32:48.000000000 -0500
@@ -19,7 +19,8 @@
#define __GFP_DMA ((__force gfp_t)0x01u)
#define __GFP_HIGHMEM ((__force gfp_t)0x02u)
#define __GFP_DMA32 ((__force gfp_t)0x04u)
-
+#define __GFP_MOVABLE ((__force gfp_t)0x08u) /* Page is movable */
+#define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE)
/*
* Action modifiers - doesn't change the zoning
*
@@ -49,7 +50,6 @@
#define __GFP_HARDWALL ((__force gfp_t)0x20000u) /* Enforce hardwall cpuset memory allocs */
#define __GFP_THISNODE ((__force gfp_t)0x40000u)/* No fallback, no policies */
#define __GFP_RECLAIMABLE ((__force gfp_t)0x80000u) /* Page is reclaimable */
-#define __GFP_MOVABLE ((__force gfp_t)0x100000u) /* Page is movable */
#define __GFP_BITS_SHIFT 21 /* Room for 21 __GFP_FOO bits */
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
@@ -111,24 +111,63 @@
((gfp_flags & __GFP_RECLAIMABLE) != 0);
}
-static inline enum zone_type gfp_zone(gfp_t flags)
-{
+#ifdef CONFIG_ZONE_HIGHMEM
+#define OPT_ZONE_HIGHMEM ZONE_HIGHMEM
+#else
+#define OPT_ZONE_HIGHMEM ZONE_NORMAL
+#endif
+
#ifdef CONFIG_ZONE_DMA
- if (flags & __GFP_DMA)
- return ZONE_DMA;
+#define OPT_ZONE_DMA ZONE_DMA
+#else
+#define OPT_ZONE_DMA ZONE_NORMAL
#endif
+
#ifdef CONFIG_ZONE_DMA32
- if (flags & __GFP_DMA32)
- return ZONE_DMA32;
+#define OPT_ZONE_DMA32 ZONE_DMA32
+#else
+#define OPT_ZONE_DMA32 OPT_ZONE_DMA
#endif
- if ((flags & (__GFP_HIGHMEM | __GFP_MOVABLE)) ==
- (__GFP_HIGHMEM | __GFP_MOVABLE))
- return ZONE_MOVABLE;
-#ifdef CONFIG_HIGHMEM
- if (flags & __GFP_HIGHMEM)
- return ZONE_HIGHMEM;
+
+#define GFP_ZONE_TABLE \
+const enum zone_type gfp_zone_table[GFP_ZONEMASK + 1] = { \
+ ZONE_NORMAL, /* 00 No flags set */ \
+ OPT_ZONE_DMA, /* 01 GFP_DMA */ \
+ OPT_ZONE_HIGHMEM, /* 02 GFP_HIGHMEM */ \
+ BAD_ZONE, /* 03 GFP_HIGHMEM GFP_DMA */ \
+ OPT_ZONE_DMA32, /* 04 GFP_DMA32 */ \
+ BAD_ZONE, /* 05 GFP_DMA32 GFP_DMA */ \
+ BAD_ZONE, /* 06 GFP_DMA32 GFP_HIGHMEM */ \
+ BAD_ZONE, /* 07 GFP_DMA32 GFP_HIGHMEM GFP_DMA */ \
+ ZONE_NORMAL, /* 08 ZONE_MOVABLE */ \
+ OPT_ZONE_DMA, /* 09 MOVABLE + DMA */ \
+ ZONE_MOVABLE, /* 0A MOVABLE + HIGHMEM */ \
+ BAD_ZONE, /* 0B MOVABLE + HIGHMEM + DMA */ \
+ OPT_ZONE_DMA32, /* 0C MOVABLE + DMA32 */ \
+ BAD_ZONE, /* 0D MOVABLE + DMA32 + DMA */ \
+ BAD_ZONE, /* 0E MOVABLE + DMA32 + HIGHMEM */ \
+ BAD_ZONE /* 0F MOVABLE + DMA32 + HIGHMEM + DMA */\
+};
+
+extern const enum zone_type gfp_zone_table[GFP_ZONEMASK + 1];
+
+static inline enum zone_type gfp_zone(gfp_t flags)
+{
+
+ if (__builtin_constant_p(flags)) {
+ GFP_ZONE_TABLE
+ enum zone_type zone = gfp_zone_table[flags & GFP_ZONEMASK];
+
+ BUILD_BUG_ON(zone == BAD_ZONE);
+ return zone;
+ } else {
+
+ enum zone_type zone = gfp_zone_table[flags & GFP_ZONEMASK];
+#ifdef CONFIG_DEBUG_VM
+ BUG_ON(zone == BAD_ZONE);
#endif
- return ZONE_NORMAL;
+ return zone;
+ }
}
/*
Index: linux-2.6/include/linux/mmzone.h
===================================================================
--- linux-2.6.orig/include/linux/mmzone.h 2009-03-19 11:47:00.000000000 -0500
+++ linux-2.6/include/linux/mmzone.h 2009-03-19 11:47:54.000000000 -0500
@@ -240,7 +240,8 @@
ZONE_HIGHMEM,
#endif
ZONE_MOVABLE,
- __MAX_NR_ZONES
+ __MAX_NR_ZONES,
+ BAD_ZONE
};
#ifndef __GENERATING_BOUNDS_H
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c 2009-03-19 13:28:35.000000000 -0500
+++ linux-2.6/mm/page_alloc.c 2009-03-19 13:32:21.000000000 -0500
@@ -67,6 +67,9 @@
};
EXPORT_SYMBOL(node_states);
+GFP_ZONE_TABLE
+EXPORT_SYMBOL(gfp_zone_table);
+
unsigned long totalram_pages __read_mostly;
unsigned long totalreserve_pages __read_mostly;
unsigned long highest_memmap_pfn __read_mostly;
--
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