From riel@redhat.com Tue Dec 18 13:21:14 2007 Date: Tue, 18 Dec 2007 16:15:53 -0500 From: Rik van Riel To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, lee.shermerhorn@hp.com, Lee Schermerhorn Subject: [patch 14/20] Scan noreclaim list for reclaimable pages V2 -> V3: + rebase to 23-mm1 atop RvR's split LRU series New in V2 This patch adds a function to scan individual or all zones' noreclaim lists and move any pages that have become reclaimable onto the respective zone's inactive list, where shrink_inactive_list() will deal with them. This replaces the function to splice the entire noreclaim list onto the active list for rescan by shrink_active_list(). That method had problems with vmstat accounting and complicated '[__]isolate_lru_pages()'. Now, __isolate_lru_page() will never isolate a non-reclaimable page. The only time it should see one is when scanning nearby pages for lumpy reclaim. TODO: This approach may still need some refinement. E.g., put back to active list? Signed-off-by: Lee Schermerhorn Signed-off-by: Rik van Riel Index: linux-2.6.24-rc4-mm1/include/linux/swap.h =================================================================== --- linux-2.6.24-rc4-mm1.orig/include/linux/swap.h +++ linux-2.6.24-rc4-mm1/include/linux/swap.h @@ -7,6 +7,7 @@ #include #include #include +#include #include #include @@ -215,12 +216,26 @@ static inline int zone_reclaim(struct zo #ifdef CONFIG_NORECLAIM extern int page_reclaimable(struct page *page, struct vm_area_struct *vma); +extern void scan_zone_noreclaim_pages(struct zone *); +extern void scan_all_zones_noreclaim_pages(void); +extern unsigned long scan_noreclaim_pages; +extern int scan_noreclaim_handler(struct ctl_table *, int, struct file *, + void __user *, size_t *, loff_t *); +extern int scan_noreclaim_register_node(struct node *node); +extern void scan_noreclaim_unregister_node(struct node *node); #else static inline int page_reclaimable(struct page *page, struct vm_area_struct *vma) { return 1; } +static inline void scan_zone_noreclaim_pages(struct zone *z) { } +static inline void scan_all_zones_noreclaim_pages(void) { } +static inline int scan_noreclaim_register_node(struct node *node) +{ + return 0; +} +static inline void scan_noreclaim_unregister_node(struct node *node) { } #endif extern int kswapd_run(int nid); Index: linux-2.6.24-rc4-mm1/mm/vmscan.c =================================================================== --- linux-2.6.24-rc4-mm1.orig/mm/vmscan.c +++ linux-2.6.24-rc4-mm1/mm/vmscan.c @@ -39,6 +39,7 @@ #include #include #include +#include #include #include @@ -2253,4 +2254,144 @@ int page_reclaimable(struct page *page, return 1; } + +/** + * scan_zone_noreclaim_pages(@zone) + * @zone - zone to scan + * + * Scan @zone's noreclaim LRU lists to check for pages that have become + * reclaimable. Move those that have to @zone's inactive list where they + * become candidates for reclaim, unless shrink_inactive_zone() decides + * to reactivate them. Pages that are still non-reclaimable are rotated + * back onto @zone's noreclaim list. + */ +#define SCAN_NORECLAIM_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ +void scan_zone_noreclaim_pages(struct zone *zone) +{ + struct list_head *l_noreclaim = &zone->list[LRU_NORECLAIM]; + struct list_head *l_inactive_anon = &zone->list[LRU_INACTIVE_ANON]; + struct list_head *l_inactive_file = &zone->list[LRU_INACTIVE_FILE]; + unsigned long scan; + unsigned long nr_to_scan = zone_page_state(zone, NR_NORECLAIM); + + while (nr_to_scan > 0) { + unsigned long batch_size = min(nr_to_scan, + SCAN_NORECLAIM_BATCH_SIZE); + + spin_lock_irq(&zone->lru_lock); + for (scan = 0; scan < batch_size; scan++) { + struct page* page = lru_to_page(l_noreclaim); + + if (unlikely(!PageLRU(page) || !PageNoreclaim(page))) + continue; + + prefetchw_prev_lru_page(page, l_noreclaim, flags); + + ClearPageNoreclaim(page); /* for page_reclaimable() */ + if(page_reclaimable(page, NULL)) { + __dec_zone_state(zone, NR_NORECLAIM); + if (page_file_cache(page)) { + list_move(&page->lru, l_inactive_file); + __inc_zone_state(zone, NR_INACTIVE_FILE); + } else { + list_move(&page->lru, l_inactive_anon); + __inc_zone_state(zone, NR_INACTIVE_ANON); + } + } else { + SetPageNoreclaim(page); + list_move(&page->lru, l_noreclaim); + } + + } + spin_unlock_irq(&zone->lru_lock); + + nr_to_scan -= batch_size; + } +} + + +/** + * scan_all_zones_noreclaim_pages() + * + * A really big hammer: scan all zones' noreclaim LRU lists to check for + * pages that have become reclaimable. Move those back to the zones' + * inactive list where they become candidates for reclaim. + * This occurs when, e.g., we have unswappable pages on the noreclaim lists, + * and we add swap to the system. As such, it runs in the context of a task + * that has possibly/probably made some previously non-reclaimable pages + * reclaimable. +//TODO: or as a last resort under extreme memory pressure--before OOM? + */ +void scan_all_zones_noreclaim_pages(void) +{ + struct zone *zone; + + for_each_zone(zone) { + scan_zone_noreclaim_pages(zone); + } +} + +/* + * scan_noreclaim_pages [vm] sysctl handler. On demand re-scan of + * all nodes' noreclaim lists for reclaimable pages + */ +unsigned long scan_noreclaim_pages; + +int scan_noreclaim_handler( struct ctl_table *table, int write, + struct file *file, void __user *buffer, + size_t *length, loff_t *ppos) +{ + proc_doulongvec_minmax(table, write, file, buffer, length, ppos); + + if (write && *(unsigned long *)table->data) + scan_all_zones_noreclaim_pages(); + + scan_noreclaim_pages = 0; + return 0; +} + +/* + * per node 'scan_noreclaim_pages' attribute. On demand re-scan of + * a specified node's per zone noreclaim lists for reclaimable pages. + */ + +static ssize_t read_scan_noreclaim_node(struct sys_device *dev, char *buf) +{ + return sprintf(buf, "0\n"); /* always zero; should fit... */ +} + +static ssize_t write_scan_noreclaim_node(struct sys_device *dev, + const char *buf, size_t count) +{ + struct zone *node_zones = NODE_DATA(dev->id)->node_zones; + struct zone *zone; + unsigned long req = simple_strtoul(buf, NULL, 10); + + if (!req) + return 1; /* zero is no-op */ + + for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { + if (!populated_zone(zone)) + continue; + scan_zone_noreclaim_pages(zone); + } + return 1; +} + + +static SYSDEV_ATTR(scan_noreclaim_pages, S_IRUGO | S_IWUSR, + read_scan_noreclaim_node, + write_scan_noreclaim_node); + +int scan_noreclaim_register_node(struct node *node) +{ + return sysdev_create_file(&node->sysdev, &attr_scan_noreclaim_pages); +} + +void scan_noreclaim_unregister_node(struct node *node) +{ + sysdev_remove_file(&node->sysdev, &attr_scan_noreclaim_pages); +} + + #endif Index: linux-2.6.24-rc4-mm1/kernel/sysctl.c =================================================================== --- linux-2.6.24-rc4-mm1.orig/kernel/sysctl.c +++ linux-2.6.24-rc4-mm1/kernel/sysctl.c @@ -1150,6 +1150,16 @@ static struct ctl_table vm_table[] = { .extra2 = &one, }, #endif +#ifdef CONFIG_NORECLAIM + { + .ctl_name = CTL_UNNUMBERED, + .procname = "scan_noreclaim_pages", + .data = &scan_noreclaim_pages, + .maxlen = sizeof(scan_noreclaim_pages), + .mode = 0644, + .proc_handler = &scan_noreclaim_handler, + }, +#endif /* * NOTE: do not add new entries to this table unless you have read * Documentation/sysctl/ctl_unnumbered.txt Index: linux-2.6.24-rc4-mm1/drivers/base/node.c =================================================================== --- linux-2.6.24-rc4-mm1.orig/drivers/base/node.c +++ linux-2.6.24-rc4-mm1/drivers/base/node.c @@ -13,6 +13,7 @@ #include #include #include +#include static struct sysdev_class node_class = { set_kset_name("node"), @@ -162,6 +163,8 @@ int register_node(struct node *node, int sysdev_create_file(&node->sysdev, &attr_meminfo); sysdev_create_file(&node->sysdev, &attr_numastat); sysdev_create_file(&node->sysdev, &attr_distance); + + scan_noreclaim_register_node(node); } return error; } @@ -180,6 +183,8 @@ void unregister_node(struct node *node) sysdev_remove_file(&node->sysdev, &attr_numastat); sysdev_remove_file(&node->sysdev, &attr_distance); + scan_noreclaim_unregister_node(node); + sysdev_unregister(&node->sysdev); } -- All Rights Reversed -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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