#include <linux/cpu.h>
#include <linux/notifier.h>
-#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
unlock_page(page);
}
+/* possible outcome of pageout() */
+typedef enum {
+ /* failed to write page out, page is locked */
+ PAGE_KEEP,
+ /* move page to the active list, page is locked */
+ PAGE_ACTIVATE,
+ /* page has been sent to the disk successfully, page is unlocked */
+ PAGE_SUCCESS,
+ /* page is clean and locked */
+ PAGE_CLEAN,
+} pageout_t;
+
/*
- * shrink_list returns the number of reclaimed pages
+ * pageout is called by shrink_list() for each dirty page. Calls ->writepage().
*/
-static int
-shrink_list(struct list_head *page_list, unsigned int gfp_mask,
- int *nr_scanned, int do_writepage)
+static pageout_t pageout(struct page *page, struct address_space *mapping)
+{
+ /*
+ * If the page is dirty, only perform writeback if that write
+ * will be non-blocking. To prevent this allocation from being
+ * stalled by pagecache activity. But note that there may be
+ * stalls if we need to run get_block(). We could test
+ * PagePrivate for that.
+ *
+ * If this process is currently in generic_file_write() against
+ * this page's queue, we can perform writeback even if that
+ * will block.
+ *
+ * If the page is swapcache, write it back even if that would
+ * block, for some throttling. This happens by accident, because
+ * swap_backing_dev_info is bust: it doesn't reflect the
+ * congestion state of the swapdevs. Easy to fix, if needed.
+ * See swapfile.c:page_queue_congested().
+ */
+ if (!is_page_cache_freeable(page))
+ return PAGE_KEEP;
+ if (!mapping)
+ return PAGE_KEEP;
+ if (mapping->a_ops->writepage == NULL)
+ return PAGE_ACTIVATE;
+ if (!may_write_to_queue(mapping->backing_dev_info))
+ return PAGE_KEEP;
+
+ if (clear_page_dirty_for_io(page)) {
+ int res;
+ struct writeback_control wbc = {
+ .sync_mode = WB_SYNC_NONE,
+ .nr_to_write = SWAP_CLUSTER_MAX,
+ .nonblocking = 1,
+ .for_reclaim = 1,
+ };
+
+ SetPageReclaim(page);
+ res = mapping->a_ops->writepage(page, &wbc);
+ if (res < 0)
+ handle_write_error(mapping, page, res);
+ if (res == WRITEPAGE_ACTIVATE) {
+ ClearPageReclaim(page);
+ return PAGE_ACTIVATE;
+ }
+ if (!PageWriteback(page)) {
+ /* synchronous write or broken a_ops? */
+ ClearPageReclaim(page);
+ }
+
+ return PAGE_SUCCESS;
+ }
+
+ return PAGE_CLEAN;
+}
+
+struct scan_control {
+ /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */
+ unsigned long nr_to_scan;
+
+ /* Incremented by the number of inactive pages that were scanned */
+ unsigned long nr_scanned;
+
+ /* Incremented by the number of pages reclaimed */
+ unsigned long nr_reclaimed;
+
+ unsigned long nr_mapped; /* From page_state */
+
+ /* Ask shrink_caches, or shrink_zone to scan at this priority */
+ unsigned int priority;
+
+ /* This context's GFP mask */
+ unsigned int gfp_mask;
+
+ int may_writepage;
+};
+
+/*
+ * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
+ */
+static int shrink_list(struct list_head *page_list, struct scan_control *sc)
{
LIST_HEAD(ret_pages);
struct pagevec freed_pvec;
int pgactivate = 0;
- int ret = 0;
+ int reclaimed = 0;
cond_resched();
if (TestSetPageLocked(page))
goto keep;
- /* Double the slab pressure for mapped and swapcache pages */
- if (page_mapped(page) || PageSwapCache(page))
- (*nr_scanned)++;
-
BUG_ON(PageActive(page));
if (PageWriteback(page))
goto keep_locked;
+ sc->nr_scanned++;
+ /* Double the slab pressure for mapped and swapcache pages */
+ if (page_mapped(page) || PageSwapCache(page))
+ sc->nr_scanned++;
+
page_map_lock(page);
referenced = page_referenced(page);
if (referenced && page_mapping_inuse(page)) {
#endif /* CONFIG_SWAP */
mapping = page_mapping(page);
- may_enter_fs = (gfp_mask & __GFP_FS) ||
- (PageSwapCache(page) && (gfp_mask & __GFP_IO));
+ may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
+ (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
/*
* The page is mapped into the page tables of one or more
}
page_map_unlock(page);
- /*
- * If the page is dirty, only perform writeback if that write
- * will be non-blocking. To prevent this allocation from being
- * stalled by pagecache activity. But note that there may be
- * stalls if we need to run get_block(). We could test
- * PagePrivate for that.
- *
- * If this process is currently in generic_file_write() against
- * this page's queue, we can perform writeback even if that
- * will block.
- *
- * If the page is swapcache, write it back even if that would
- * block, for some throttling. This happens by accident, because
- * swap_backing_dev_info is bust: it doesn't reflect the
- * congestion state of the swapdevs. Easy to fix, if needed.
- * See swapfile.c:page_queue_congested().
- */
if (PageDirty(page)) {
if (referenced)
goto keep_locked;
- if (!is_page_cache_freeable(page))
- goto keep_locked;
- if (!mapping)
- goto keep_locked;
- if (mapping->a_ops->writepage == NULL)
- goto activate_locked;
if (!may_enter_fs)
goto keep_locked;
- if (!may_write_to_queue(mapping->backing_dev_info))
+ if (laptop_mode && !sc->may_writepage)
goto keep_locked;
- if (laptop_mode && !do_writepage)
+
+ /* Page is dirty, try to write it out here */
+ switch(pageout(page, mapping)) {
+ case PAGE_KEEP:
goto keep_locked;
- if (clear_page_dirty_for_io(page)) {
- int res;
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- .nr_to_write = SWAP_CLUSTER_MAX,
- .nonblocking = 1,
- .for_reclaim = 1,
- };
-
- SetPageReclaim(page);
- res = mapping->a_ops->writepage(page, &wbc);
- if (res < 0)
- handle_write_error(mapping, page, res);
- if (res == WRITEPAGE_ACTIVATE) {
- ClearPageReclaim(page);
- goto activate_locked;
- }
- if (!PageWriteback(page)) {
- /* synchronous write or broken a_ops? */
- ClearPageReclaim(page);
- }
- goto keep;
+ case PAGE_ACTIVATE:
+ goto activate_locked;
+ case PAGE_SUCCESS:
+ if (PageWriteback(page) || PageDirty(page))
+ goto keep;
+ /*
+ * A synchronous write - probably a ramdisk. Go
+ * ahead and try to reclaim the page.
+ */
+ if (TestSetPageLocked(page))
+ goto keep;
+ if (PageDirty(page) || PageWriteback(page))
+ goto keep_locked;
+ mapping = page_mapping(page);
+ case PAGE_CLEAN:
+ ; /* try to free the page below */
}
}
* the pages which were not successfully invalidated in
* truncate_complete_page(). We try to drop those buffers here
* and if that worked, and the page is no longer mapped into
- * process address space (page_count == 0) it can be freed.
+ * process address space (page_count == 1) it can be freed.
* Otherwise, leave the page on the LRU so it is swappable.
*/
if (PagePrivate(page)) {
- if (!try_to_release_page(page, gfp_mask))
+ if (!try_to_release_page(page, sc->gfp_mask))
goto activate_locked;
if (!mapping && page_count(page) == 1)
goto free_it;
free_it:
unlock_page(page);
- ret++;
+ reclaimed++;
if (!pagevec_add(&freed_pvec, page))
__pagevec_release_nonlru(&freed_pvec);
continue;
if (pagevec_count(&freed_pvec))
__pagevec_release_nonlru(&freed_pvec);
mod_page_state(pgactivate, pgactivate);
- return ret;
+ sc->nr_reclaimed += reclaimed;
+ return reclaimed;
}
/*
* a batch of pages and working on them outside the lock. Any pages which were
* not freed will be added back to the LRU.
*
- * shrink_cache() is passed the number of pages to scan and returns the number
- * of pages which were reclaimed.
+ * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
*
* For pagecache intensive workloads, the first loop here is the hottest spot
* in the kernel (apart from the copy_*_user functions).
*/
-static int
-shrink_cache(struct zone *zone, unsigned int gfp_mask,
- int max_scan, int *total_scanned, int do_writepage)
+static void shrink_cache(struct zone *zone, struct scan_control *sc)
{
LIST_HEAD(page_list);
struct pagevec pvec;
- int ret = 0;
+ int max_scan = sc->nr_to_scan;
pagevec_init(&pvec, 1);
mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
else
mod_page_state_zone(zone, pgscan_direct, nr_scan);
- nr_freed = shrink_list(&page_list, gfp_mask,
- total_scanned, do_writepage);
- *total_scanned += nr_taken;
+ nr_freed = shrink_list(&page_list, sc);
if (current_is_kswapd())
mod_page_state(kswapd_steal, nr_freed);
mod_page_state_zone(zone, pgsteal, nr_freed);
- ret += nr_freed;
- if (nr_freed <= 0 && list_empty(&page_list))
- goto done;
-
spin_lock_irq(&zone->lru_lock);
/*
* Put back any unfreeable pages.
spin_unlock_irq(&zone->lru_lock);
done:
pagevec_release(&pvec);
- return ret;
}
/*
* But we had to alter page->flags anyway.
*/
static void
-refill_inactive_zone(struct zone *zone, const int nr_pages_in,
- struct page_state *ps)
+refill_inactive_zone(struct zone *zone, struct scan_control *sc)
{
int pgmoved;
int pgdeactivate = 0;
- int nr_pages = nr_pages_in;
+ int pgscanned = 0;
+ int nr_pages = sc->nr_to_scan;
LIST_HEAD(l_hold); /* The pages which were snipped off */
LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
LIST_HEAD(l_active); /* Pages to go onto the active_list */
lru_add_drain();
pgmoved = 0;
spin_lock_irq(&zone->lru_lock);
- while (nr_pages && !list_empty(&zone->active_list)) {
+ while (pgscanned < nr_pages && !list_empty(&zone->active_list)) {
page = lru_to_page(&zone->active_list);
prefetchw_prev_lru_page(page, &zone->active_list, flags);
if (!TestClearPageLRU(page))
list_add(&page->lru, &l_hold);
pgmoved++;
}
- nr_pages--;
+ pgscanned++;
}
zone->nr_active -= pgmoved;
spin_unlock_irq(&zone->lru_lock);
* mapped memory instead of just pagecache. Work out how much memory
* is mapped.
*/
- mapped_ratio = (ps->nr_mapped * 100) / total_memory;
+ mapped_ratio = (sc->nr_mapped * 100) / total_memory;
/*
* Now decide how much we really want to unmap some pages. The mapped
spin_unlock_irq(&zone->lru_lock);
pagevec_release(&pvec);
- mod_page_state_zone(zone, pgrefill, nr_pages_in - nr_pages);
+ mod_page_state_zone(zone, pgrefill, pgscanned);
mod_page_state(pgdeactivate, pgdeactivate);
}
* Scan `nr_pages' from this zone. Returns the number of reclaimed pages.
* This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
*/
-static int
-shrink_zone(struct zone *zone, int max_scan, unsigned int gfp_mask,
- int *total_scanned, struct page_state *ps, int do_writepage)
+static void
+shrink_zone(struct zone *zone, struct scan_control *sc)
{
- unsigned long scan_active;
+ unsigned long scan_active, scan_inactive;
int count;
+ scan_inactive = (zone->nr_active + zone->nr_inactive) >> sc->priority;
+
/*
* Try to keep the active list 2/3 of the size of the cache. And
* make sure that refill_inactive is given a decent number of pages.
*/
if (zone->nr_active >= 4*(zone->nr_inactive*2 + 1)) {
/* Don't scan more than 4 times the inactive list scan size */
- scan_active = 4*max_scan;
+ scan_active = 4*scan_inactive;
} else {
unsigned long long tmp;
/* Cast to long long so the multiply doesn't overflow */
- tmp = (unsigned long long)max_scan * zone->nr_active;
+ tmp = (unsigned long long)scan_inactive * zone->nr_active;
do_div(tmp, zone->nr_inactive*2 + 1);
scan_active = (unsigned long)tmp;
}
count = atomic_read(&zone->nr_scan_active);
if (count >= SWAP_CLUSTER_MAX) {
atomic_set(&zone->nr_scan_active, 0);
- refill_inactive_zone(zone, count, ps);
+ sc->nr_to_scan = count;
+ refill_inactive_zone(zone, sc);
}
- atomic_add(max_scan, &zone->nr_scan_inactive);
+ atomic_add(scan_inactive, &zone->nr_scan_inactive);
count = atomic_read(&zone->nr_scan_inactive);
if (count >= SWAP_CLUSTER_MAX) {
atomic_set(&zone->nr_scan_inactive, 0);
- return shrink_cache(zone, gfp_mask, count,
- total_scanned, do_writepage);
+ sc->nr_to_scan = count;
+ shrink_cache(zone, sc);
}
- return 0;
}
/*
* If a zone is deemed to be full of pinned pages then just give it a light
* scan then give up on it.
*/
-static int
-shrink_caches(struct zone **zones, int priority, int *total_scanned,
- int gfp_mask, struct page_state *ps, int do_writepage)
+static void
+shrink_caches(struct zone **zones, struct scan_control *sc)
{
- int ret = 0;
int i;
for (i = 0; zones[i] != NULL; i++) {
struct zone *zone = zones[i];
- int max_scan;
- if (zone->free_pages < zone->pages_high)
- zone->temp_priority = priority;
+ zone->temp_priority = sc->priority;
+ if (zone->prev_priority > sc->priority)
+ zone->prev_priority = sc->priority;
- if (zone->all_unreclaimable && priority != DEF_PRIORITY)
+ if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
continue; /* Let kswapd poll it */
- max_scan = (zone->nr_active + zone->nr_inactive) >> priority;
- ret += shrink_zone(zone, max_scan, gfp_mask,
- total_scanned, ps, do_writepage);
+ shrink_zone(zone, sc);
}
- return ret;
}
/*
*
* If the caller is !__GFP_FS then the probability of a failure is reasonably
* high - the zone may be full of dirty or under-writeback pages, which this
- * caller can't do much about. So for !__GFP_FS callers, we just perform a
- * small LRU walk and if that didn't work out, fail the allocation back to the
- * caller. GFP_NOFS allocators need to know how to deal with it. Kicking
- * bdflush, waiting and retrying will work.
- *
- * This is a fairly lame algorithm - it can result in excessive CPU burning and
- * excessive rotation of the inactive list, which is _supposed_ to be an LRU,
- * yes?
+ * caller can't do much about. We kick pdflush and take explicit naps in the
+ * hope that some of these pages can be written. But if the allocating task
+ * holds filesystem locks which prevent writeout this might not work, and the
+ * allocation attempt will fail.
*/
int try_to_free_pages(struct zone **zones,
unsigned int gfp_mask, unsigned int order)
{
int priority;
int ret = 0;
- int nr_reclaimed = 0;
+ int total_scanned = 0, total_reclaimed = 0;
struct reclaim_state *reclaim_state = current->reclaim_state;
+ struct scan_control sc;
int i;
- unsigned long total_scanned = 0;
- int do_writepage = 0;
+
+ sc.gfp_mask = gfp_mask;
+ sc.may_writepage = 0;
inc_page_state(allocstall);
zones[i]->temp_priority = DEF_PRIORITY;
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
- int scanned = 0;
- struct page_state ps;
-
- get_page_state(&ps);
- nr_reclaimed += shrink_caches(zones, priority, &scanned,
- gfp_mask, &ps, do_writepage);
- shrink_slab(scanned, gfp_mask);
+ sc.nr_mapped = read_page_state(nr_mapped);
+ sc.nr_scanned = 0;
+ sc.nr_reclaimed = 0;
+ sc.priority = priority;
+ shrink_caches(zones, &sc);
+ shrink_slab(sc.nr_scanned, gfp_mask);
if (reclaim_state) {
- nr_reclaimed += reclaim_state->reclaimed_slab;
+ sc.nr_reclaimed += reclaim_state->reclaimed_slab;
reclaim_state->reclaimed_slab = 0;
}
- if (nr_reclaimed >= SWAP_CLUSTER_MAX) {
+ if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) {
ret = 1;
goto out;
}
- if (!(gfp_mask & __GFP_FS))
- break; /* Let the caller handle it */
+ total_scanned += sc.nr_scanned;
+ total_reclaimed += sc.nr_reclaimed;
+
/*
* Try to write back as many pages as we just scanned. This
* tends to cause slow streaming writers to write data to the
* that's undesirable in laptop mode, where we *want* lumpy
* writeout. So in laptop mode, write out the whole world.
*/
- total_scanned += scanned;
if (total_scanned > SWAP_CLUSTER_MAX + SWAP_CLUSTER_MAX/2) {
wakeup_bdflush(laptop_mode ? 0 : total_scanned);
- do_writepage = 1;
+ sc.may_writepage = 1;
}
/* Take a nap, wait for some writeback to complete */
- if (scanned && priority < DEF_PRIORITY - 2)
+ if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
blk_congestion_wait(WRITE, HZ/10);
}
if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY))
* the page allocator fallback scheme to ensure that aging of pages is balanced
* across the zones.
*/
-static int balance_pgdat(pg_data_t *pgdat, int nr_pages, struct page_state *ps)
+static int balance_pgdat(pg_data_t *pgdat, int nr_pages)
{
int to_free = nr_pages;
int priority;
int i;
+ int total_scanned = 0, total_reclaimed = 0;
struct reclaim_state *reclaim_state = current->reclaim_state;
- unsigned long total_scanned = 0;
- unsigned long total_reclaimed = 0;
- int do_writepage = 0;
+ struct scan_control sc;
+
+ sc.gfp_mask = GFP_KERNEL;
+ sc.may_writepage = 0;
+ sc.nr_mapped = read_page_state(nr_mapped);
inc_page_state(pageoutrun);
zone->temp_priority = DEF_PRIORITY;
}
- for (priority = DEF_PRIORITY; priority; priority--) {
+ for (priority = DEF_PRIORITY; priority >= 0; priority--) {
int all_zones_ok = 1;
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
*/
for (i = 0; i <= end_zone; i++) {
struct zone *zone = pgdat->node_zones + i;
- int max_scan;
- int reclaimed;
- int scanned = 0;
if (zone->all_unreclaimable && priority != DEF_PRIORITY)
continue;
all_zones_ok = 0;
}
zone->temp_priority = priority;
- max_scan = (zone->nr_active + zone->nr_inactive)
- >> priority;
- reclaimed = shrink_zone(zone, max_scan, GFP_KERNEL,
- &scanned, ps, do_writepage);
- total_scanned += scanned;
+ if (zone->prev_priority > priority)
+ zone->prev_priority = priority;
+ sc.nr_scanned = 0;
+ sc.nr_reclaimed = 0;
+ sc.priority = priority;
+ shrink_zone(zone, &sc);
reclaim_state->reclaimed_slab = 0;
- shrink_slab(scanned, GFP_KERNEL);
- reclaimed += reclaim_state->reclaimed_slab;
- total_reclaimed += reclaimed;
- to_free -= reclaimed;
+ shrink_slab(sc.nr_scanned, GFP_KERNEL);
+ sc.nr_reclaimed += reclaim_state->reclaimed_slab;
+ total_reclaimed += sc.nr_reclaimed;
if (zone->all_unreclaimable)
continue;
if (zone->pages_scanned > zone->present_pages * 2)
*/
if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
total_scanned > total_reclaimed+total_reclaimed/2)
- do_writepage = 1;
+ sc.may_writepage = 1;
}
- if (nr_pages && to_free > 0)
+ if (nr_pages && to_free > total_reclaimed)
continue; /* swsusp: need to do more work */
if (all_zones_ok)
break; /* kswapd: all done */
tsk->flags |= PF_MEMALLOC|PF_KSWAPD;
for ( ; ; ) {
- struct page_state ps;
-
if (current->flags & PF_FREEZE)
refrigerator(PF_FREEZE);
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
schedule();
finish_wait(&pgdat->kswapd_wait, &wait);
try_to_clip_inodes();
- get_page_state(&ps);
- balance_pgdat(pgdat, 0, &ps);
+
+ balance_pgdat(pgdat, 0);
}
}
current->reclaim_state = &reclaim_state;
for_each_pgdat(pgdat) {
int freed;
- struct page_state ps;
-
- get_page_state(&ps);
- freed = balance_pgdat(pgdat, nr_to_free, &ps);
+ freed = balance_pgdat(pgdat, nr_to_free);
ret += freed;
nr_to_free -= freed;
if (nr_to_free <= 0)
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