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Subject[PATCH 1/2] MM cleanups
Date

The attached patch does some cleaning up of the MM code preparatory to
overhauling the high-order page handling:

(1) Trailing spaces have been cleaned up on lines in page_alloc.c and
bootmem.c.

(2) bootmem.c now has a separate path to release pages to the main allocator
that bypasses many of the checks performed on struct pages.

(3) __pagevec_free() has moved to swap.c with all the other pagevec
functions.

(4) put_page() has moved to page_alloc.c with all the other related
functions. This could be relegated to a separate file, but since there
are many other conditionals in page_alloc.c, what's the point?

Signed-Off-By: David Howells <dhowells@redhat.com>
---
warthog>diffstat mmcleanup-2610rc2mm3.diff
bootmem.c | 35 ++++++++-------
internal.h | 3 -
page_alloc.c | 136 +++++++++++++++++++++++++++++++++++++----------------------
swap.c | 29 +++---------
4 files changed, 116 insertions(+), 87 deletions(-)
diff -uNrp /warthog/kernels/linux-2.6.10-rc2-mm3/mm/bootmem.c linux-2.6.10-rc2-mm3-mmcleanup/mm/bootmem.c
--- /warthog/kernels/linux-2.6.10-rc2-mm3/mm/bootmem.c 2004-11-22 10:54:17.000000000 +0000
+++ linux-2.6.10-rc2-mm3-mmcleanup/mm/bootmem.c 2004-11-23 15:32:12.964968405 +0000
@@ -89,7 +89,7 @@ static void __init reserve_bootmem_core(
* fully reserved.
*/
unsigned long sidx = (addr - bdata->node_boot_start)/PAGE_SIZE;
- unsigned long eidx = (addr + size - bdata->node_boot_start +
+ unsigned long eidx = (addr + size - bdata->node_boot_start +
PAGE_SIZE-1)/PAGE_SIZE;
unsigned long end = (addr + size + PAGE_SIZE-1)/PAGE_SIZE;

@@ -174,7 +174,7 @@ __alloc_bootmem_core(struct bootmem_data
* We try to allocate bootmem pages above 'goal'
* first, then we try to allocate lower pages.
*/
- if (goal && (goal >= bdata->node_boot_start) &&
+ if (goal && (goal >= bdata->node_boot_start) &&
((goal >> PAGE_SHIFT) < bdata->node_low_pfn)) {
preferred = goal - bdata->node_boot_start;

@@ -264,7 +264,7 @@ static unsigned long __init free_all_boo
bootmem_data_t *bdata = pgdat->bdata;
unsigned long i, count, total = 0;
unsigned long idx;
- unsigned long *map;
+ unsigned long *map;
int gofast = 0;

BUG_ON(!bdata->node_bootmem_map);
@@ -274,55 +274,59 @@ static unsigned long __init free_all_boo
page = virt_to_page(phys_to_virt(bdata->node_boot_start));
idx = bdata->node_low_pfn - (bdata->node_boot_start >> PAGE_SHIFT);
map = bdata->node_bootmem_map;
+
/* Check physaddr is O(LOG2(BITS_PER_LONG)) page aligned */
if (bdata->node_boot_start == 0 ||
ffs(bdata->node_boot_start) - PAGE_SHIFT > ffs(BITS_PER_LONG))
gofast = 1;
+
for (i = 0; i < idx; ) {
unsigned long v = ~map[i / BITS_PER_LONG];
+
if (gofast && v == ~0UL) {
int j, order;

count += BITS_PER_LONG;
__ClearPageReserved(page);
order = ffs(BITS_PER_LONG) - 1;
- set_page_refs(page, order);
for (j = 1; j < BITS_PER_LONG; j++) {
if (j + 16 < BITS_PER_LONG)
prefetchw(page + j + 16);
__ClearPageReserved(page + j);
}
- __free_pages(page, order);
+ __free_pages_bootmem(page, order);
i += BITS_PER_LONG;
page += BITS_PER_LONG;
+
} else if (v) {
unsigned long m;
for (m = 1; m && i < idx; m<<=1, page++, i++) {
if (v & m) {
count++;
__ClearPageReserved(page);
- set_page_refs(page, 0);
- __free_page(page);
+ __free_pages_bootmem(page, 0);
}
}
+
} else {
- i+=BITS_PER_LONG;
+ i += BITS_PER_LONG;
page += BITS_PER_LONG;
}
}
total += count;

/*
- * Now free the allocator bitmap itself, it's not
- * needed anymore:
+ * Now free the allocator bitmap itself, it's not needed anymore:
*/
page = virt_to_page(bdata->node_bootmem_map);
- count = 0;
- for (i = 0; i < ((bdata->node_low_pfn-(bdata->node_boot_start >> PAGE_SHIFT))/8 + PAGE_SIZE-1)/PAGE_SIZE; i++,page++) {
- count++;
+
+ count = bdata->node_low_pfn - (bdata->node_boot_start >> PAGE_SHIFT);
+ count = ((count / 8) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+ for (i = count; i > 0; i--) {
__ClearPageReserved(page);
- set_page_count(page, 1);
- __free_page(page);
+ __free_pages_bootmem(page, 0);
+ page++;
}
total += count;
bdata->node_bootmem_map = NULL;
@@ -402,4 +406,3 @@ void * __init __alloc_bootmem_node (pg_d

return __alloc_bootmem(size, align, goal);
}
-
diff -uNrp /warthog/kernels/linux-2.6.10-rc2-mm3/mm/internal.h linux-2.6.10-rc2-mm3-mmcleanup/mm/internal.h
--- /warthog/kernels/linux-2.6.10-rc2-mm3/mm/internal.h 2004-11-22 10:54:18.000000000 +0000
+++ linux-2.6.10-rc2-mm3-mmcleanup/mm/internal.h 2004-11-23 15:31:55.601409553 +0000
@@ -10,4 +10,5 @@
*/

/* page_alloc.c */
-extern void set_page_refs(struct page *page, int order);
+extern void fastcall free_hot_cold_page(struct page *page, int cold);
+extern fastcall void __init __free_pages_bootmem(struct page *page, unsigned int order);
diff -uNrp /warthog/kernels/linux-2.6.10-rc2-mm3/mm/page_alloc.c linux-2.6.10-rc2-mm3-mmcleanup/mm/page_alloc.c
--- /warthog/kernels/linux-2.6.10-rc2-mm3/mm/page_alloc.c 2004-11-22 10:54:18.000000000 +0000
+++ linux-2.6.10-rc2-mm3-mmcleanup/mm/page_alloc.c 2004-11-23 16:13:04.184628888 +0000
@@ -103,6 +103,23 @@ static void bad_page(const char *functio
tainted |= TAINT_BAD_PAGE;
}

+void set_page_refs(struct page *page, int order)
+{
+#ifdef CONFIG_MMU
+ set_page_count(page, 1);
+#else
+ int i;
+
+ /*
+ * We need to reference all the pages for this order, otherwise if
+ * anyone accesses one of the pages with (get/put) it will be freed.
+ * - eg: access_process_vm()
+ */
+ for (i = 0; i < (1 << order); i++)
+ set_page_count(page + i, 1);
+#endif /* CONFIG_MMU */
+}
+
#ifndef CONFIG_HUGETLB_PAGE
#define prep_compound_page(page, order) do { } while (0)
#define destroy_compound_page(page, order) do { } while (0)
@@ -167,11 +184,13 @@ static void destroy_compound_page(struct
* zone->lock is already acquired when we use these.
* So, we don't need atomic page->flags operations here.
*/
-static inline unsigned long page_order(struct page *page) {
+static inline unsigned long page_order(struct page *page)
+{
return page->private;
}

-static inline void set_page_order(struct page *page, int order) {
+static inline void set_page_order(struct page *page, int order)
+{
page->private = order;
__SetPagePrivate(page);
}
@@ -217,10 +236,10 @@ static inline int page_is_buddy(struct p
* free pages of length of (1 << order) and marked with PG_Private.Page's
* order is recorded in page->private field.
* So when we are allocating or freeing one, we can derive the state of the
- * other. That is, if we allocate a small block, and both were
- * free, the remainder of the region must be split into blocks.
+ * other. That is, if we allocate a small block, and both were
+ * free, the remainder of the region must be split into blocks.
* If a block is freed, and its buddy is also free, then this
- * triggers coalescing into a block of larger size.
+ * triggers coalescing into a block of larger size.
*
* -- wli
*/
@@ -286,7 +305,7 @@ static inline void free_pages_check(cons
}

/*
- * Frees a list of pages.
+ * Frees a list of pages.
* Assumes all pages on list are in same zone, and of same order.
* count is the number of pages to free, or 0 for all on the list.
*
@@ -337,10 +356,33 @@ void __free_pages_ok(struct page *page,
for (i = 0 ; i < (1 << order) ; ++i)
free_pages_check(__FUNCTION__, page + i);
list_add(&page->lru, &list);
- kernel_map_pages(page, 1<<order, 0);
+ kernel_map_pages(page, 1 << order, 0);
free_pages_bulk(page_zone(page), 1, &list, order);
}

+/*
+ * permit the bootmem allocator to evade page validation on high-order frees
+ */
+fastcall void __init __free_pages_bootmem(struct page *page, unsigned int order)
+{
+ set_page_refs(page, order);
+ set_page_count(page, 0);
+
+ if (order == 0) {
+ free_hot_cold_page(page, 0);
+ } else {
+ LIST_HEAD(list);
+
+ arch_free_page(page, order);
+
+ mod_page_state(pgfree, 1 << order);
+
+ list_add(&page->lru, &list);
+ kernel_map_pages(page, 1 << order, 0);
+ free_pages_bulk(page_zone(page), 1, &list, order);
+ }
+}
+

/*
* The order of subdivision here is critical for the IO subsystem.
@@ -374,23 +416,6 @@ expand(struct zone *zone, struct page *p
return page;
}

-void set_page_refs(struct page *page, int order)
-{
-#ifdef CONFIG_MMU
- set_page_count(page, 1);
-#else
- int i;
-
- /*
- * We need to reference all the pages for this order, otherwise if
- * anyone accesses one of the pages with (get/put) it will be freed.
- * - eg: access_process_vm()
- */
- for (i = 0; i < (1 << order); i++)
- set_page_count(page + i, 1);
-#endif /* CONFIG_MMU */
-}
-
/*
* This page is about to be returned from the page allocator
*/
@@ -415,7 +440,7 @@ static void prep_new_page(struct page *p
set_page_refs(page, order);
}

-/*
+/*
* Do the hard work of removing an element from the buddy allocator.
* Call me with the zone->lock already held.
*/
@@ -441,19 +466,19 @@ static struct page *__rmqueue(struct zon
return NULL;
}

-/*
+/*
* Obtain a specified number of elements from the buddy allocator, all under
* a single hold of the lock, for efficiency. Add them to the supplied list.
* Returns the number of new pages which were placed at *list.
*/
-static int rmqueue_bulk(struct zone *zone, unsigned int order,
+static int rmqueue_bulk(struct zone *zone, unsigned int order,
unsigned long count, struct list_head *list)
{
unsigned long flags;
int i;
int allocated = 0;
struct page *page;
-
+
spin_lock_irqsave(&zone->lock, flags);
for (i = 0; i < count; ++i) {
page = __rmqueue(zone, order);
@@ -517,9 +542,9 @@ void drain_local_pages(void)
{
unsigned long flags;

- local_irq_save(flags);
+ local_irq_save(flags);
__drain_pages(smp_processor_id());
- local_irq_restore(flags);
+ local_irq_restore(flags);
}
#endif /* CONFIG_PM */

@@ -552,8 +577,7 @@ static void zone_statistics(struct zonel
/*
* Free a 0-order page
*/
-static void FASTCALL(free_hot_cold_page(struct page *page, int cold));
-static void fastcall free_hot_cold_page(struct page *page, int cold)
+void fastcall free_hot_cold_page(struct page *page, int cold)
{
struct zone *zone = page_zone(page);
struct per_cpu_pages *pcp;
@@ -580,7 +604,7 @@ void fastcall free_hot_page(struct page
{
free_hot_cold_page(page, 0);
}
-
+
void fastcall free_cold_page(struct page *page)
{
free_hot_cold_page(page, 1);
@@ -957,14 +981,6 @@ fastcall unsigned long get_zeroed_page(u

EXPORT_SYMBOL(get_zeroed_page);

-void __pagevec_free(struct pagevec *pvec)
-{
- int i = pagevec_count(pvec);
-
- while (--i >= 0)
- free_hot_cold_page(pvec->pages[i], pvec->cold);
-}
-
fastcall void __free_pages(struct page *page, unsigned int order)
{
if (!PageReserved(page) && put_page_testzero(page)) {
@@ -987,6 +1003,26 @@ fastcall void free_pages(unsigned long a

EXPORT_SYMBOL(free_pages);

+#ifdef CONFIG_HUGETLB_PAGE
+
+void put_page(struct page *page)
+{
+ if (unlikely(PageCompound(page))) {
+ page = (struct page *)page->private;
+ if (put_page_testzero(page)) {
+ void (*dtor)(struct page *page);
+
+ dtor = (void (*)(struct page *))page[1].mapping;
+ (*dtor)(page);
+ }
+ return;
+ }
+ if (!PageReserved(page) && put_page_testzero(page))
+ __page_cache_release(page);
+}
+EXPORT_SYMBOL(put_page);
+#endif
+
/*
* Total amount of free (allocatable) RAM:
*/
@@ -1498,7 +1534,7 @@ static void __init build_zonelists(pg_da
j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
for (node = 0; node < local_node; node++)
j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
-
+
zonelist->zones[j] = NULL;
}
}
@@ -1636,7 +1672,7 @@ static void __init free_area_init_core(s
pgdat->nr_zones = 0;
init_waitqueue_head(&pgdat->kswapd_wait);
pgdat->kswapd_max_order = 0;
-
+
for (j = 0; j < MAX_NR_ZONES; j++) {
struct zone *zone = pgdat->node_zones + j;
unsigned long size, realsize;
@@ -1798,7 +1834,7 @@ static void frag_stop(struct seq_file *m
{
}

-/*
+/*
* This walks the free areas for each zone.
*/
static int frag_show(struct seq_file *m, void *arg)
@@ -2038,8 +2074,8 @@ static void setup_per_zone_protection(vo
}

/*
- * setup_per_zone_pages_min - called when min_free_kbytes changes. Ensures
- * that the pages_{min,low,high} values for each zone are set correctly
+ * setup_per_zone_pages_min - called when min_free_kbytes changes. Ensures
+ * that the pages_{min,low,high} values for each zone are set correctly
* with respect to min_free_kbytes.
*/
static void setup_per_zone_pages_min(void)
@@ -2073,10 +2109,10 @@ static void setup_per_zone_pages_min(voi
min_pages = 128;
zone->pages_min = min_pages;
} else {
- /* if it's a lowmem zone, reserve a number of pages
+ /* if it's a lowmem zone, reserve a number of pages
* proportionate to the zone's size.
*/
- zone->pages_min = (pages_min * zone->present_pages) /
+ zone->pages_min = (pages_min * zone->present_pages) /
lowmem_pages;
}

@@ -2132,11 +2168,11 @@ static int __init init_per_zone_pages_mi
module_init(init_per_zone_pages_min)

/*
- * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
+ * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
* that we can call two helper functions whenever min_free_kbytes
* changes.
*/
-int min_free_kbytes_sysctl_handler(ctl_table *table, int write,
+int min_free_kbytes_sysctl_handler(ctl_table *table, int write,
struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
{
proc_dointvec(table, write, file, buffer, length, ppos);
diff -uNrp /warthog/kernels/linux-2.6.10-rc2-mm3/mm/swap.c linux-2.6.10-rc2-mm3-mmcleanup/mm/swap.c
--- /warthog/kernels/linux-2.6.10-rc2-mm3/mm/swap.c 2004-11-22 10:54:18.000000000 +0000
+++ linux-2.6.10-rc2-mm3-mmcleanup/mm/swap.c 2004-11-23 15:31:55.602409470 +0000
@@ -30,30 +30,11 @@
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/init.h>
+#include "internal.h"

/* How many pages do we try to swap or page in/out together? */
int page_cluster;

-#ifdef CONFIG_HUGETLB_PAGE
-
-void put_page(struct page *page)
-{
- if (unlikely(PageCompound(page))) {
- page = (struct page *)page->private;
- if (put_page_testzero(page)) {
- void (*dtor)(struct page *page);
-
- dtor = (void (*)(struct page *))page[1].mapping;
- (*dtor)(page);
- }
- return;
- }
- if (!PageReserved(page) && put_page_testzero(page))
- __page_cache_release(page);
-}
-EXPORT_SYMBOL(put_page);
-#endif
-
/*
* Writeback is about to end against a page which has been marked for immediate
* reclaim. If it still appears to be reclaimable, move it to the tail of the
@@ -242,6 +223,14 @@ void release_pages(struct page **pages,
pagevec_free(&pages_to_free);
}

+void __pagevec_free(struct pagevec *pvec)
+{
+ int i = pagevec_count(pvec);
+
+ while (--i >= 0)
+ free_hot_cold_page(pvec->pages[i], pvec->cold);
+}
+
/*
* The pages which we're about to release may be in the deferred lru-addition
* queues. That would prevent them from really being freed right now. That's
-
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