This patch optmizes replace_page_cache_page.
1) remove radix_tree_preload
2) single radix_tree_lookup_slot and replace radix tree slot
3) page accounting optimization if both pages are in same zone.
Cc: Miklos Szeredi <mszeredi@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
---
mm/filemap.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++---------
1 files changed, 51 insertions(+), 10 deletions(-)
Hi Miklos,
This patch is totally not tested.
Could you test this patch?
diff --git a/mm/filemap.c b/mm/filemap.c
index a25c898..918ef1e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -148,6 +148,56 @@ void __remove_from_page_cache(struct page *page)
}
}
+/*
+ * Replace a page from the page cache with a new one.
+ * Both the old and new page must be locked.
+ * The caller must hold the mapping's tree_lock.
+ */
+void __replace_page_cache_page(struct page *old, struct page *new)
+{
+ void **pslot;
+ struct address_space *mapping = old->mapping;
+ struct zone *old_zone, *new_zone;
+
+ old_zone = page_zone(old);
+ new_zone = page_zone(new);
+ /*
+ * if we're uptodate, flush out into the cleancache, otherwise
+ * invalidate any existing cleancache entries. We can't leave
+ * stale data around in the cleancache once our page is gone
+ */
+ if (PageUptodate(old))
+ cleancache_put_page(old);
+ else
+ cleancache_flush_page(mapping, old);
+
+ pslot = radix_tree_lookup_slot(&mapping->page_tree,
+ page_index(old));
+ get_page(new); /* add cache reference */
+ radix_tree_replace_slot(pslot, new);
+ old->mapping = NULL;
+ if (old_zone != new_zone) {
+ __dec_zone_page_state(old, NR_FILE_PAGES);
+ __inc_zone_page_state(new, NR_FILE_PAGES);
+ if (PageSwapBacked(old)) {
+ __dec_zone_page_state(old, NR_SHMEM);
+ __inc_zone_page_state(new, NR_SHMEM);
+ }
+ }
+ BUG_ON(page_mapped(old));
+ /*
+ * Some filesystems seem to re-dirty the page even after
+ * the VM has canceled the dirty bit (eg ext3 journaling).
+ *
+ * Fix it up by doing a final dirty accounting check after
+ * having removed the page entirely.
+ */
+ if (PageDirty(old) && mapping_cap_account_dirty(mapping)) {
+ dec_zone_page_state(old, NR_FILE_DIRTY);
+ dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
+ }
+}
+
void remove_from_page_cache(struct page *page)
{
struct address_space *mapping = page->mapping;
@@ -433,7 +483,6 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
if (error)
return error;
- error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
if (!error) {
struct address_space *mapping = old->mapping;
void (*freepage)(struct page *);
@@ -441,20 +490,12 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
pgoff_t offset = old->index;
freepage = mapping->a_ops->freepage;
- page_cache_get(new);
new->mapping = mapping;
new->index = offset;
spin_lock_irq(&mapping->tree_lock);
- __remove_from_page_cache(old);
- error = radix_tree_insert(&mapping->page_tree, offset, new);
- BUG_ON(error);
- mapping->nrpages++;
- __inc_zone_page_state(new, NR_FILE_PAGES);
- if (PageSwapBacked(new))
- __inc_zone_page_state(new, NR_SHMEM);
+ __replace_page_cache_page(old, new);
spin_unlock_irq(&mapping->tree_lock);
- radix_tree_preload_end();
if (freepage)
freepage(old);
page_cache_release(old);
--
1.7.1
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