merging swap prefetching

diff -puN include/linux/mm_inline.h~mm-implement-swap-prefetching include/linux/mm_inline.h
@@ -14,6 +14,13 @@ add_page_to_inactive_list(struct zone *z
 }
 
 static inline void
+add_page_to_inactive_list_tail(struct zone *zone, struct page *page)
+{
+	list_add_tail(&page->lru, &zone->inactive_list);
+	zone->nr_inactive++;
+}
+
+static inline void
 del_page_from_active_list(struct zone *zone, struct page *page)
 {
 	list_del(&page->lru);

diff -puN include/linux/swap.h~mm-implement-swap-prefetching include/linux/swap.h
@@ -173,6 +173,7 @@ extern unsigned int nr_free_pagecache_pa
 /* linux/mm/swap.c */
 extern void FASTCALL(lru_cache_add(struct page *));
 extern void FASTCALL(lru_cache_add_active(struct page *));
+extern void FASTCALL(lru_cache_add_tail(struct page *));
 extern void FASTCALL(activate_page(struct page *));
 extern void FASTCALL(mark_page_accessed(struct page *));
 extern void lru_add_drain(void);

@@ -228,6 +229,7 @@ extern void free_pages_and_swap_cache(st
 extern struct page * lookup_swap_cache(swp_entry_t);
 extern struct page * read_swap_cache_async(swp_entry_t, struct vm_area_struct *vma,
 					   unsigned long addr);
+extern int add_to_swap_cache(struct page *page, swp_entry_t entry);
 /* linux/mm/swapfile.c */
 extern long total_swap_pages;
 extern unsigned int nr_swapfiles;

diff -puN include/linux/sysctl.h~mm-implement-swap-prefetching include/linux/sysctl.h
@@ -191,9 +191,9 @@ enum
 	VM_ZONE_RECLAIM_MODE=31, /* reclaim local zone memory before going off node */
 	VM_PANIC_ON_OOM=33,	/* panic at out-of-memory */
 	VM_VDSO_ENABLED=34,	/* map VDSO into new processes? */
+	VM_SWAP_PREFETCH=35,	/* swap prefetch */
 };
 
-
 /* CTL_NET names: */
 enum
 {

diff -puN kernel/sysctl.c~mm-implement-swap-prefetching kernel/sysctl.c
@@ -23,6 +23,7 @@
 #include <linux/mm.h>
 #include <linux/swap.h>
 #include <linux/slab.h>
+#include <linux/swap-prefetch.h>
 #include <linux/sysctl.h>
 #include <linux/proc_fs.h>
 #include <linux/capability.h>

@@ -948,6 +949,16 @@ static ctl_table vm_table[] = {
 		.extra1		= &zero,
 	},
 #endif
+#ifdef CONFIG_SWAP_PREFETCH
+	{
+		.ctl_name	= VM_SWAP_PREFETCH,
+		.procname	= "swap_prefetch",
+		.data		= &swap_prefetch,
+		.maxlen		= sizeof(swap_prefetch),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+#endif
 	{ .ctl_name = 0 }
 };
 

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diff -puN mm/swap_state.c~mm-implement-swap-prefetching mm/swap_state.c
@@ -10,6 +10,7 @@
 #include <linux/mm.h>
 #include <linux/kernel_stat.h>
 #include <linux/swap.h>
+#include <linux/swap-prefetch.h>
 #include <linux/init.h>
 #include <linux/pagemap.h>
 #include <linux/buffer_head.h>

@@ -82,6 +83,7 @@ static int __add_to_swap_cache(struct pa
 		error = radix_tree_insert(&swapper_space.page_tree,
 						entry.val, page);
 		if (!error) {
+			remove_from_swapped_list(entry.val);
 			page_cache_get(page);
 			SetPageLocked(page);
 			SetPageSwapCache(page);

@@ -95,11 +97,12 @@ static int __add_to_swap_cache(struct pa
 	return error;
 }
 
-static int add_to_swap_cache(struct page *page, swp_entry_t entry)
+int add_to_swap_cache(struct page *page, swp_entry_t entry)
 {
 	int error;
 
 	if (!swap_duplicate(entry)) {
+		remove_from_swapped_list(entry.val);
 		INC_CACHE_INFO(noent_race);
 		return -ENOENT;
 	}

@@ -148,6 +151,9 @@ int add_to_swap(struct page * page, gfp_
 	swp_entry_t entry;
 	int err;
 
+	/* Swap prefetching is delayed if we're swapping pages */
+	delay_swap_prefetch();
+
 	BUG_ON(!PageLocked(page));
 
 	for (;;) {

@@ -320,6 +326,9 @@ struct page *read_swap_cache_async(swp_e
 	struct page *found_page, *new_page = NULL;
 	int err;
 
+	/* Swap prefetching is delayed if we're already reading from swap */
+	delay_swap_prefetch();
+
 	do {
 		/*
 		 * First check the swap cache.  Since this is normally

diff -puN mm/vmscan.c~mm-implement-swap-prefetching mm/vmscan.c
@@ -16,6 +16,7 @@
 #include <linux/slab.h>
 #include <linux/kernel_stat.h>
 #include <linux/swap.h>
+#include <linux/swap-prefetch.h>
 #include <linux/pagemap.h>
 #include <linux/init.h>
 #include <linux/highmem.h>

@@ -395,6 +396,7 @@ int remove_mapping(struct address_space 
 
 	if (PageSwapCache(page)) {
 		swp_entry_t swap = { .val = page_private(page) };
+		add_to_swapped_list(page);
 		__delete_from_swap_cache(page);
 		write_unlock_irq(&mapping->tree_lock);
 		swap_free(swap);

@@ -975,6 +977,7 @@ unsigned long try_to_free_pages(struct z
 		.swappiness = vm_swappiness,
 	};
 
+	delay_swap_prefetch();
 	count_vm_event(ALLOCSTALL);
 
 	for (i = 0; zones[i] != NULL; i++) {

@@ -1356,6 +1359,8 @@ unsigned long shrink_all_memory(unsigned
 		.swappiness = vm_swappiness,
 	};
 
+	delay_swap_prefetch();
+
 	current->reclaim_state = &reclaim_state;
 
 	lru_pages = 0;

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