Hi,
(Sent this to linux-mm only and waited... I have not got it back yet
more than 2 h later - resending it to linux-kernel too)
This is a embryotic, but with heart beats, patch of page ageing
for test3-pre6.
Features:
* does NOT add any field in page structure.
* round robin lists is used to simulate ageing.
* referenced pages are moved 5 steps forward.
* non freeable, tryagain, are moved 3 steps forward.
* new pages are inserted 2 steps forward.
* no pages are moved backward or to currently scanned.
Future work:
* trim offsets / size / priority
* remove code that unnecessary sets page as referenced (riel?)
* add more offsets depending on why the page could not
be freed.
* split pagemap_lru_lock (if wanted on SMP)
* move pages of zones with pressure less forward...
* ...
/RogerL
-- Home page: http://www.norran.net/nra02596/
--- linux/mm/page_alloc.c.orig Mon Jul 10 11:46:29 2000 +++ linux/mm/page_alloc.c Mon Jul 10 11:46:44 2000 @@ -499,7 +499,7 @@ void __init free_area_init_core(int nid, freepages.min += i; freepages.low += i * 2; freepages.high += i * 3; - memlist_init(&lru_cache); + init_lru_cache(); /* * Some architectures (with lots of mem and discontinous memory --- linux/include/linux/mm.h.orig Mon Jul 10 11:38:52 2000 +++ linux/include/linux/mm.h Mon Jul 10 11:49:07 2000 @@ -15,7 +15,7 @@ extern unsigned long max_mapnr; extern unsigned long num_physpages; extern void * high_memory; extern int page_cluster; -extern struct list_head lru_cache; +extern struct list_head *lru_cache_insert; #include <asm/page.h> #include <asm/pgtable.h> @@ -456,6 +456,7 @@ struct zone_t; /* filemap.c */ extern void remove_inode_page(struct page *); extern unsigned long page_unuse(struct page *); +extern void init_lru_cache(void); extern int shrink_mmap(int, int); extern void truncate_inode_pages(struct address_space *, loff_t); --- linux/include/linux/swap.h.orig Mon Jul 10 11:43:03 2000 +++ linux/include/linux/swap.h Mon Jul 10 11:44:45 2000 @@ -166,7 +166,7 @@ extern spinlock_t pagemap_lru_lock; #define lru_cache_add(page) \ do { \ spin_lock(&pagemap_lru_lock); \ - list_add(&(page)->lru, &lru_cache); \ + list_add(&(page)->lru, lru_cache_insert); \ nr_lru_pages++; \ spin_unlock(&pagemap_lru_lock); \ } while (0) --- linux/mm/filemap.c.orig Mon Jul 10 11:02:59 2000 +++ linux/mm/filemap.c Mon Jul 10 23:10:08 2000 @@ -44,7 +44,17 @@ atomic_t page_cache_size = ATOMIC_INIT(0); unsigned int page_hash_bits; struct page **page_hash_table; -struct list_head lru_cache; +/* Note: optimization possibility - spit pagemap_lru_lock! + * iff LRU_INSERT_OFFSET != 0 and != all other offsets */ +#define NO_LRU_CACHES 8 /* power of two, greater than biggest offset */ +#define LRU_SCAN_INIT 0 +#define LRU_INSERT_OFFSET 2 +#define LRU_REFERENCED_OFFSET 5 +#define LRU_TRYAGAIN_OFFSET 3 +static struct list_head lru_caches[NO_LRU_CACHES]; +static unsigned lru_scan = LRU_SCAN_INIT; +struct list_head *lru_cache_insert = + &lru_caches[(LRU_SCAN_INIT + LRU_INSERT_OFFSET) % NO_LRU_CACHES]; static spinlock_t pagecache_lock = SPIN_LOCK_UNLOCKED; /* @@ -245,6 +255,15 @@ repeat: spin_unlock(&pagecache_lock); } + +void init_lru_cache(void) +{ + int ix; + + for (ix = 0; ix < NO_LRU_CACHES; ix++) + INIT_LIST_HEAD(&lru_caches[ix]); +} + /* * nr_dirty represents the number of dirty pages that we will write async * before doing sync writes. We can only do sync writes if we can @@ -253,6 +272,7 @@ repeat: int shrink_mmap(int priority, int gfp_mask) { int ret = 0, count, nr_dirty; + static struct list_head *lru_cache_scan = &lru_caches[LRU_SCAN_INIT]; struct list_head * page_lru; struct page * page = NULL; @@ -261,12 +281,17 @@ int shrink_mmap(int priority, int gfp_ma /* we need pagemap_lru_lock for list_del() ... subtle code below */ spin_lock(&pagemap_lru_lock); - while (count > 0 && (page_lru = lru_cache.prev) != &lru_cache) { + again: + while (count > 0 && + (page_lru = lru_cache_scan->prev) != lru_cache_scan) { + unsigned dispose_offset; page = list_entry(page_lru, struct page, lru); list_del(page_lru); + dispose_offset = LRU_REFERENCED_OFFSET; if (PageTestandClearReferenced(page)) goto dispose_continue; + dispose_offset = LRU_TRYAGAIN_OFFSET; count--; /* @@ -354,9 +379,31 @@ unlock_continue: UnlockPage(page); page_cache_release(page); dispose_continue: - list_add(page_lru, &lru_cache); + { + /* TODO CHECK OPTIMIZATION + * should become + * (lru_scan + dispose_offset) & (NO_LRU_CACHES - 1) + * since both lru_scan and dispose_offset are unsigned + * and NO_LRU_CACHES is a power of two. + */ + unsigned dispose = + (lru_scan + dispose_offset) % NO_LRU_CACHES; + + list_add(page_lru, + &lru_caches[dispose]); + } } - goto out; + if (count == 0) + goto out; + + printk(KERN_DEBUG "scan wrap\n"); + lru_scan = (lru_scan + 1) % NO_LRU_CACHES; + + lru_cache_scan = &lru_caches[lru_scan]; + lru_cache_insert = + &lru_caches[(lru_scan + LRU_INSERT_OFFSET) % NO_LRU_CACHES]; + + goto again; made_inode_progress: page_cache_release(page);
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This archive was generated by hypermail 2b29 : Sat Jul 15 2000 - 21:00:11 EST