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Subjectswsusp: Kill O(n^2) algorithm in swsusp
Hi!

Some machines are spending minutes of CPU time during suspend in
stupid O(n^2) algorithm. This patch replaces it with O(n) algorithm,
making swsusp usable to some people.

I'd like people to test this. It should probably spend few weeks
in -mm tree to get some beating. OTOH SUSE has variant of this patch
in its kernel.

Signed-off-by: Pavel Machek <pavel@suse.cz>

Pavel

--- clean-cvs/include/linux/page-flags.h 2004-08-24 20:26:54.000000000 +0200
+++ linux-cvs/include/linux/page-flags.h 2004-12-10 22:35:58.000000000 +0100
@@ -74,7 +74,7 @@
#define PG_swapcache 16 /* Swap page: swp_entry_t in private */
#define PG_mappedtodisk 17 /* Has blocks allocated on-disk */
#define PG_reclaim 18 /* To be reclaimed asap */
-
+#define PG_nosave_free 19 /* Page is free and should not be written */

/*
* Global page accounting. One instance per CPU. Only unsigned longs are
@@ -277,6 +277,10 @@
#define ClearPageNosave(page) clear_bit(PG_nosave, &(page)->flags)
#define TestClearPageNosave(page) test_and_clear_bit(PG_nosave, &(page)->flags)

+#define PageNosaveFree(page) test_bit(PG_nosave_free, &(page)->flags)
+#define SetPageNosaveFree(page) set_bit(PG_nosave_free, &(page)->flags)
+#define ClearPageNosaveFree(page) clear_bit(PG_nosave_free, &(page)->flags)
+
#define PageMappedToDisk(page) test_bit(PG_mappedtodisk, &(page)->flags)
#define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
#define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)
--- clean-cvs/include/linux/suspend.h 2004-09-29 22:04:50.000000000 +0200
+++ linux-cvs/include/linux/suspend.h 2004-12-10 22:35:58.000000000 +0100
@@ -31,6 +31,7 @@

/* mm/page_alloc.c */
extern void drain_local_pages(void);
+extern void mark_free_pages(struct zone *zone);

/* kernel/power/swsusp.c */
extern int software_suspend(void);
--- clean-cvs/kernel/power/swsusp.c 2004-12-14 20:43:42.000000000 +0100
+++ linux-cvs/kernel/power/swsusp.c 2004-12-14 20:48:31.000000000 +0100
@@ -74,11 +74,9 @@
/* References to section boundaries */
extern char __nosave_begin, __nosave_end;

-extern int is_head_of_free_region(struct page *);
-
/* Variables to be preserved over suspend */
-int pagedir_order_check;
-int nr_copy_pages_check;
+static int pagedir_order_check;
+static int nr_copy_pages_check;

extern char resume_file[];
static dev_t resume_device;
@@ -426,12 +424,12 @@
static int save_highmem_zone(struct zone *zone)
{
unsigned long zone_pfn;
+ mark_free_pages(zone);
for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
struct page *page;
struct highmem_page *save;
void *kaddr;
unsigned long pfn = zone_pfn + zone->zone_start_pfn;
- int chunk_size;

if (!(pfn%1000))
printk(".");
@@ -448,11 +446,9 @@
printk("highmem reserved page?!\n");
continue;
}
- if ((chunk_size = is_head_of_free_region(page))) {
- pfn += chunk_size - 1;
- zone_pfn += chunk_size - 1;
+ BUG_ON(PageNosave(page));
+ if (PageNosaveFree(page))
continue;
- }
save = kmalloc(sizeof(struct highmem_page), GFP_ATOMIC);
if (!save)
return -ENOMEM;
@@ -524,21 +520,16 @@
* We save a page if it's Reserved, and not in the range of pages
* statically defined as 'unsaveable', or if it isn't reserved, and
* isn't part of a free chunk of pages.
- * If it is part of a free chunk, we update @pfn to point to the last
- * page of the chunk.
*/

static int saveable(struct zone * zone, unsigned long * zone_pfn)
{
unsigned long pfn = *zone_pfn + zone->zone_start_pfn;
- unsigned long chunk_size;
struct page * page;

if (!pfn_valid(pfn))
return 0;

- if (!(pfn%1000))
- printk(".");
page = pfn_to_page(pfn);
BUG_ON(PageReserved(page) && PageNosave(page));
if (PageNosave(page))
@@ -547,10 +538,8 @@
pr_debug("[nosave pfn 0x%lx]", pfn);
return 0;
}
- if ((chunk_size = is_head_of_free_region(page))) {
- *zone_pfn += chunk_size - 1;
+ if (PageNosaveFree(page))
return 0;
- }

return 1;
}
@@ -563,10 +552,11 @@
nr_copy_pages = 0;

for_each_zone(zone) {
- if (!is_highmem(zone)) {
- for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
- nr_copy_pages += saveable(zone, &zone_pfn);
- }
+ if (is_highmem(zone))
+ continue;
+ mark_free_pages(zone);
+ for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
+ nr_copy_pages += saveable(zone, &zone_pfn);
}
}

@@ -576,52 +566,25 @@
struct zone *zone;
unsigned long zone_pfn;
struct pbe * pbe = pagedir_nosave;
+ int to_copy = nr_copy_pages;

for_each_zone(zone) {
- if (!is_highmem(zone))
- for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
- if (saveable(zone, &zone_pfn)) {
- struct page * page;
- page = pfn_to_page(zone_pfn + zone->zone_start_pfn);
- pbe->orig_address = (long) page_address(page);
- /* copy_page is no usable for copying task structs. */
- memcpy((void *)pbe->address, (void *)pbe->orig_address, PAGE_SIZE);
- pbe++;
- }
- }
- }
-}
-
-
-static void free_suspend_pagedir_zone(struct zone *zone, unsigned long pagedir)
-{
- unsigned long zone_pfn, pagedir_end, pagedir_pfn, pagedir_end_pfn;
- pagedir_end = pagedir + (PAGE_SIZE << pagedir_order);
- pagedir_pfn = __pa(pagedir) >> PAGE_SHIFT;
- pagedir_end_pfn = __pa(pagedir_end) >> PAGE_SHIFT;
- for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
- struct page *page;
- unsigned long pfn = zone_pfn + zone->zone_start_pfn;
- if (!pfn_valid(pfn))
- continue;
- page = pfn_to_page(pfn);
- if (!TestClearPageNosave(page))
- continue;
- else if (pfn >= pagedir_pfn && pfn < pagedir_end_pfn)
+ if (is_highmem(zone))
continue;
- __free_page(page);
- }
-}
-
-void swsusp_free(void)
-{
- unsigned long p = (unsigned long)pagedir_save;
- struct zone *zone;
- for_each_zone(zone) {
- if (!is_highmem(zone))
- free_suspend_pagedir_zone(zone, p);
+ mark_free_pages(zone);
+ for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
+ if (saveable(zone, &zone_pfn)) {
+ struct page * page;
+ page = pfn_to_page(zone_pfn + zone->zone_start_pfn);
+ pbe->orig_address = (long) page_address(page);
+ /* copy_page is not usable for copying task structs. */
+ memcpy((void *)pbe->address, (void *)pbe->orig_address, PAGE_SIZE);
+ pbe++;
+ to_copy--;
+ }
+ }
}
- free_pages(p, pagedir_order);
+ BUG_ON(to_copy);
}


@@ -687,6 +650,24 @@
return 0;
}

+/**
+ * free_image_pages - Free pages allocated for snapshot
+ */
+
+static void free_image_pages(void)
+{
+ struct pbe * p;
+ int i;
+
+ p = pagedir_save;
+ for (i = 0, p = pagedir_save; i < nr_copy_pages; i++, p++) {
+ if (p->address) {
+ ClearPageNosave(virt_to_page(p->address));
+ free_page(p->address);
+ p->address = 0;
+ }
+ }
+}

/**
* alloc_image_pages - Allocate pages for the snapshot.
@@ -700,18 +681,19 @@

for (i = 0, p = pagedir_save; i < nr_copy_pages; i++, p++) {
p->address = get_zeroed_page(GFP_ATOMIC | __GFP_COLD);
- if(!p->address)
- goto Error;
+ if (!p->address)
+ return -ENOMEM;
SetPageNosave(virt_to_page(p->address));
}
return 0;
- Error:
- do {
- if (p->address)
- free_page(p->address);
- p->address = 0;
- } while (p-- > pagedir_save);
- return -ENOMEM;
+}
+
+void swsusp_free(void)
+{
+ BUG_ON(PageNosave(virt_to_page(pagedir_save)));
+ BUG_ON(PageNosaveFree(virt_to_page(pagedir_save)));
+ free_image_pages();
+ free_pages((unsigned long) pagedir_save, pagedir_order);
}


@@ -1113,6 +1087,7 @@
return -EPERM;
}
nr_copy_pages = swsusp_info.image_pages;
+ pagedir_order = get_bitmask_order(SUSPEND_PD_PAGES(nr_copy_pages));
return error;
}

@@ -1179,9 +1154,7 @@
int i, n = swsusp_info.pagedir_pages;
int error = 0;

- pagedir_order = get_bitmask_order(n);
-
- addr =__get_free_pages(GFP_ATOMIC, pagedir_order);
+ addr = __get_free_pages(GFP_ATOMIC, pagedir_order);
if (!addr)
return -ENOMEM;
pagedir_nosave = (struct pbe *)addr;
--- clean-cvs/mm/page_alloc.c 2004-11-19 12:54:54.000000000 +0100
+++ linux-cvs/mm/page_alloc.c 2004-12-10 22:35:59.000000000 +0100
@@ -437,26 +437,30 @@
#endif /* CONFIG_PM || CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_PM
-int is_head_of_free_region(struct page *page)
+
+void mark_free_pages(struct zone *zone)
{
- struct zone *zone = page_zone(page);
- unsigned long flags;
+ unsigned long zone_pfn, flags;
int order;
struct list_head *curr;

- /*
- * Should not matter as we need quiescent system for
- * suspend anyway, but...
- */
+ if (!zone->spanned_pages)
+ return;
+
spin_lock_irqsave(&zone->lock, flags);
+ for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
+ ClearPageNosaveFree(pfn_to_page(zone_pfn + zone->zone_start_pfn));
+
for (order = MAX_ORDER - 1; order >= 0; --order)
- list_for_each(curr, &zone->free_area[order].free_list)
- if (page == list_entry(curr, struct page, lru)) {
- spin_unlock_irqrestore(&zone->lock, flags);
- return 1 << order;
- }
+ list_for_each(curr, &zone->free_area[order].free_list) {
+ unsigned long start_pfn, i;
+
+ start_pfn = page_to_pfn(list_entry(curr, struct page, lru));
+
+ for (i=0; i < (1<<order); i++)
+ SetPageNosaveFree(pfn_to_page(start_pfn+i));
+ }
spin_unlock_irqrestore(&zone->lock, flags);
- return 0;
}

/*

--
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!
-
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