Re: [PATCH] Simplify node/zone field in page->flags

Matthew Dobson
2004-01-05T22:42:21Z

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Jesse Barnes wrote:
> On Mon, Jan 05, 2004 at 01:22:57PM -0800, Matthew Dobson wrote:
>
>>Jesse had acked the patch in an earlier itteration. The only thing
>>that's changed is some line offsets whilst porting the patch forward.
>>
>>Jesse (or anyone else?), any objections to this patch as a superset of
>>yours?
>
>
> No objections here. Of course, you'll have to rediff against the
> current tree since that stuff has been merged for awhile now. On a
> somewhat related note, Martin mentioned that he'd like to get rid of
> memblks. I'm all for that too; they just seem to get in the way.
>
> Jesse
>

Yeah... didn't actually attatch the patch to that last email, did I?
Brain slowly transitioning back into "on" mode after a couple weeks
solidly in the "off" position.

-Matt

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diff -Nurp --exclude-from=/home/mcd/.dontdiff linux-2.6.1-rc1/include/linux/mm.h linux-2.6.1-rc1+nodezone/include/linux/mm.h
--- linux-2.6.1-rc1/include/linux/mm.h Mon Jan 5 12:36:24 2004
+++ linux-2.6.1-rc1+nodezone/include/linux/mm.h Mon Jan 5 14:26:28 2004
@@ -322,23 +322,33 @@ static inline void put_page(struct page
/*
* The zone field is never updated after free_area_init_core()
* sets it, so none of the operations on it need to be atomic.
- * We'll have up to log2(MAX_NUMNODES * MAX_NR_ZONES) zones
- * total, so we use NODES_SHIFT here to get enough bits.
+ * We'll have up to (MAX_NUMNODES * MAX_NR_ZONES) zones total,
+ * so we use (MAX_NODES_SHIFT + MAX_ZONES_SHIFT) here to get enough bits.
*/
-#define ZONE_SHIFT (BITS_PER_LONG - NODES_SHIFT - MAX_NR_ZONES_SHIFT)
+#define NODEZONE_SHIFT (BITS_PER_LONG - MAX_NODES_SHIFT - MAX_ZONES_SHIFT)
+#define NODEZONE(node, zone) ((node << ZONES_SHIFT) | zone)
+
+static inline unsigned long page_zonenum(struct page *page)
+{
+ return (page->flags >> NODEZONE_SHIFT) & (~(~0UL << ZONES_SHIFT));
+}
+static inline unsigned long page_nodenum(struct page *page)
+{
+ return (page->flags >> NODEZONE_SHIFT + ZONES_SHIFT);
+}

struct zone;
extern struct zone *zone_table[];

static inline struct zone *page_zone(struct page *page)
{
- return zone_table[page->flags >> ZONE_SHIFT];
+ return zone_table[page->flags >> NODEZONE_SHIFT];
}

-static inline void set_page_zone(struct page *page, unsigned long zone_num)
+static inline void set_page_zone(struct page *page, unsigned long nodezone_num)
{
- page->flags &= ~(~0UL << ZONE_SHIFT);
- page->flags |= zone_num << ZONE_SHIFT;
+ page->flags &= ~(~0UL << NODEZONE_SHIFT);
+ page->flags |= nodezone_num << NODEZONE_SHIFT;
}

#ifndef CONFIG_DISCONTIGMEM
diff -Nurp --exclude-from=/home/mcd/.dontdiff linux-2.6.1-rc1/include/linux/mmzone.h linux-2.6.1-rc1+nodezone/include/linux/mmzone.h
--- linux-2.6.1-rc1/include/linux/mmzone.h Mon Jan 5 12:36:24 2004
+++ linux-2.6.1-rc1+nodezone/include/linux/mmzone.h Mon Jan 5 14:04:46 2004
@@ -160,8 +160,8 @@ struct zone {
#define ZONE_NORMAL 1
#define ZONE_HIGHMEM 2

-#define MAX_NR_ZONES 3 /* Sync this with MAX_NR_ZONES_SHIFT */
-#define MAX_NR_ZONES_SHIFT 2 /* ceil(log2(MAX_NR_ZONES)) */
+#define MAX_NR_ZONES 3 /* Sync this with ZONES_SHIFT */
+#define ZONES_SHIFT 2 /* ceil(log2(MAX_NR_ZONES)) */

#define GFP_ZONEMASK 0x03

@@ -311,7 +311,7 @@ extern struct pglist_data contig_page_da

#if BITS_PER_LONG == 32
/*
- * with 32 bit flags field, page->zone is currently 8 bits.
+ * with 32 bit page->flags field, we reserve 8 bits for node/zone info.
* there are 3 zones (2 bits) and this leaves 8-2=6 bits for nodes.
*/
#define MAX_NODES_SHIFT 6
@@ -328,6 +328,13 @@ extern struct pglist_data contig_page_da
#error NODES_SHIFT > MAX_NODES_SHIFT
#endif

+/* There are currently 3 zones: DMA, Normal & Highmem, thus we need 2 bits */
+#define MAX_ZONES_SHIFT 2
+
+#if ZONES_SHIFT > MAX_ZONES_SHIFT
+#error ZONES_SHIFT > MAX_ZONES_SHIFT
+#endif
+
extern DECLARE_BITMAP(node_online_map, MAX_NUMNODES);
extern DECLARE_BITMAP(memblk_online_map, MAX_NR_MEMBLKS);

diff -Nurp --exclude-from=/home/mcd/.dontdiff linux-2.6.1-rc1/mm/page_alloc.c linux-2.6.1-rc1+nodezone/mm/page_alloc.c
--- linux-2.6.1-rc1/mm/page_alloc.c Mon Jan 5 12:36:24 2004
+++ linux-2.6.1-rc1+nodezone/mm/page_alloc.c Mon Jan 5 14:04:46 2004
@@ -50,7 +50,7 @@ EXPORT_SYMBOL(nr_swap_pages);
* Used by page_zone() to look up the address of the struct zone whose
* id is encoded in the upper bits of page->flags
*/
-struct zone *zone_table[MAX_NR_ZONES*MAX_NUMNODES];
+struct zone *zone_table[1 << (ZONES_SHIFT + NODES_SHIFT)];
EXPORT_SYMBOL(zone_table);

static char *zone_names[MAX_NR_ZONES] = { "DMA", "Normal", "HighMem" };
@@ -1212,7 +1212,7 @@ void __init memmap_init_zone(struct page
struct page *page;

for (page = start; page < (start + size); page++) {
- set_page_zone(page, nid * MAX_NR_ZONES + zone);
+ set_page_zone(page, NODEZONE(nid, zone));
set_page_count(page, 0);
SetPageReserved(page);
INIT_LIST_HEAD(&page->list);
@@ -1253,7 +1253,7 @@ static void __init free_area_init_core(s
unsigned long size, realsize;
unsigned long batch;

- zone_table[nid * MAX_NR_ZONES + j] = zone;
+ zone_table[NODEZONE(nid, j)] = zone;
realsize = size = zones_size[j];
if (zholes_size)
realsize -= zholes_size[j];