diff options
Diffstat (limited to 'mm/swap.c')
| -rw-r--r-- | mm/swap.c | 254 |
1 files changed, 251 insertions, 3 deletions
@@ -40,7 +40,18 @@ freepages_t freepages = { }; /* How many pages do we try to swap or page in/out together? */ -int page_cluster = 4; /* Default value modified in swap_setup() */ +int page_cluster; + +/* + * This variable contains the amount of page steals the system + * is doing, averaged over a minute. We use this to determine how + * many inactive pages we should have. + * + * In reclaim_page and __alloc_pages: memory_pressure++ + * In __free_pages_ok: memory_pressure-- + * In recalculate_vm_stats the value is decayed (once a second) + */ +int memory_pressure; /* We track the number of pages currently being asynchronously swapped out, so that we don't try to swap TOO many pages out at once */ @@ -61,13 +72,250 @@ buffer_mem_t page_cache = { pager_daemon_t pager_daemon = { 512, /* base number for calculating the number of tries */ SWAP_CLUSTER_MAX, /* minimum number of tries */ - SWAP_CLUSTER_MAX, /* do swap I/O in clusters of this size */ + 8, /* do swap I/O in clusters of this size */ }; +/** + * age_page_{up,down} - page aging helper functions + * @page - the page we want to age + * @nolock - are we already holding the pagelist_lru_lock? + * + * If the page is on one of the lists (active, inactive_dirty or + * inactive_clean), we will grab the pagelist_lru_lock as needed. + * If you're already holding the lock, call this function with the + * nolock argument non-zero. + */ +void age_page_up_nolock(struct page * page) +{ + /* + * We're dealing with an inactive page, move the page + * to the active list. + */ + if (!page->age) + activate_page_nolock(page); + + /* The actual page aging bit */ + page->age += PAGE_AGE_ADV; + if (page->age > PAGE_AGE_MAX) + page->age = PAGE_AGE_MAX; +} + /* - * Perform any setup for the swap system + * We use this (minimal) function in the case where we + * know we can't deactivate the page (yet). */ +void age_page_down_ageonly(struct page * page) +{ + page->age /= 2; +} + +void age_page_down_nolock(struct page * page) +{ + /* The actual page aging bit */ + page->age /= 2; + + /* + * The page is now an old page. Move to the inactive + * list (if possible ... see below). + */ + if (!page->age) + deactivate_page_nolock(page); +} +void age_page_up(struct page * page) +{ + /* + * We're dealing with an inactive page, move the page + * to the active list. + */ + if (!page->age) + activate_page(page); + + /* The actual page aging bit */ + page->age += PAGE_AGE_ADV; + if (page->age > PAGE_AGE_MAX) + page->age = PAGE_AGE_MAX; +} + +void age_page_down(struct page * page) +{ + /* The actual page aging bit */ + page->age /= 2; + + /* + * The page is now an old page. Move to the inactive + * list (if possible ... see below). + */ + if (!page->age) + deactivate_page(page); +} + + +/** + * (de)activate_page - move pages from/to active and inactive lists + * @page: the page we want to move + * @nolock - are we already holding the pagemap_lru_lock? + * + * Deactivate_page will move an active page to the right + * inactive list, while activate_page will move a page back + * from one of the inactive lists to the active list. If + * called on a page which is not on any of the lists, the + * page is left alone. + */ +void deactivate_page_nolock(struct page * page) +{ + /* + * One for the cache, one for the extra reference the + * caller has and (maybe) one for the buffers. + * + * This isn't perfect, but works for just about everything. + * Besides, as long as we don't move unfreeable pages to the + * inactive_clean list it doesn't need to be perfect... + */ + int maxcount = (page->buffers ? 3 : 2); + page->age = 0; + + /* + * Don't touch it if it's not on the active list. + * (some pages aren't on any list at all) + */ + if (PageActive(page) && page_count(page) <= maxcount && + !page_ramdisk(page)) { + + /* + * We can move the page to the inactive_dirty list + * if we have the strong suspicion that they might + * become freeable in the near future. + * + * That is, the page has buffer heads attached (that + * need to be cleared away) and/or the function calling + * us has an extra reference count on the page. + */ + if (page->buffers || page_count(page) == 2) { + del_page_from_active_list(page); + add_page_to_inactive_dirty_list(page); + /* + * Only if we are SURE the page is clean and immediately + * reusable, we move it to the inactive_clean list. + */ + } else if (page->mapping && !PageDirty(page) && + !PageLocked(page)) { + del_page_from_active_list(page); + add_page_to_inactive_clean_list(page); + } + /* + * OK, we cannot free the page. Leave it alone. + */ + } +} + +void deactivate_page(struct page * page) +{ + spin_lock(&pagemap_lru_lock); + deactivate_page_nolock(page); + spin_unlock(&pagemap_lru_lock); +} + +/* + * Move an inactive page to the active list. + */ +void activate_page_nolock(struct page * page) +{ + if (PageInactiveDirty(page)) { + del_page_from_inactive_dirty_list(page); + add_page_to_active_list(page); + } else if (PageInactiveClean(page)) { + del_page_from_inactive_clean_list(page); + add_page_to_active_list(page); + } else { + /* + * The page was not on any list, so we take care + * not to do anything. + */ + } + + /* Make sure the page gets a fair chance at staying active. */ + if (page->age < PAGE_AGE_START) + page->age = PAGE_AGE_START; +} + +void activate_page(struct page * page) +{ + spin_lock(&pagemap_lru_lock); + activate_page_nolock(page); + spin_unlock(&pagemap_lru_lock); +} + +/** + * lru_cache_add: add a page to the page lists + * @page: the page to add + */ +void lru_cache_add(struct page * page) +{ + spin_lock(&pagemap_lru_lock); + if (!PageLocked(page)) + BUG(); + DEBUG_ADD_PAGE + add_page_to_active_list(page); + /* This should be relatively rare */ + if (!page->age) + deactivate_page_nolock(page); + spin_unlock(&pagemap_lru_lock); +} + +/** + * __lru_cache_del: remove a page from the page lists + * @page: the page to add + * + * This function is for when the caller already holds + * the pagemap_lru_lock. + */ +void __lru_cache_del(struct page * page) +{ + if (PageActive(page)) { + del_page_from_active_list(page); + } else if (PageInactiveDirty(page)) { + del_page_from_inactive_dirty_list(page); + } else if (PageInactiveClean(page)) { + del_page_from_inactive_clean_list(page); + } else { + printk("VM: __lru_cache_del, found unknown page ?!\n"); + } + DEBUG_ADD_PAGE +} + +/** + * lru_cache_del: remove a page from the page lists + * @page: the page to remove + */ +void lru_cache_del(struct page * page) +{ + if (!PageLocked(page)) + BUG(); + spin_lock(&pagemap_lru_lock); + __lru_cache_del(page); + spin_unlock(&pagemap_lru_lock); +} + +/** + * recalculate_vm_stats - recalculate VM statistics + * + * This function should be called once a second to recalculate + * some useful statistics the VM subsystem uses to determine + * its behaviour. + */ +void recalculate_vm_stats(void) +{ + /* + * Substract one second worth of memory_pressure from + * memory_pressure. + */ + memory_pressure -= (memory_pressure >> INACTIVE_SHIFT); +} + +/* + * Perform any setup for the swap system + */ void __init swap_setup(void) { /* Use a smaller cluster for memory <16MB or <32MB */ |