hot-n-cold pages: use cold pages for readahead

ChangeSet 1.910, 2002/10/30 15:36:03-08:00, akpm@digeo.com

	[PATCH] hot-n-cold pages: use cold pages for readahead
	
	It is usually the case that pagecache reads use busmastering hardware
	to transfer the data into pagecache.  This invalidates the CPU cache of
	the pagecache pages.
	
	So use cache-cold pages for pagecache reads.  To avoid wasting
	cache-hot pages.


# This patch includes the following deltas:
#	           ChangeSet	1.909   -> 1.910  
#	include/linux/pagemap.h	1.28    -> 1.29   
#	      mm/readahead.c	1.18    -> 1.19   
#	        mm/filemap.c	1.151   -> 1.152  
#

 include/linux/pagemap.h |    5 +++++
 mm/filemap.c            |    6 +++---
 mm/readahead.c          |    2 +-
 3 files changed, 9 insertions(+), 4 deletions(-)


diff -Nru a/include/linux/pagemap.h b/include/linux/pagemap.h
--- a/include/linux/pagemap.h	Wed Oct 30 16:21:58 2002
+++ b/include/linux/pagemap.h	Wed Oct 30 16:21:58 2002
@@ -31,6 +31,11 @@
 	return alloc_pages(x->gfp_mask, 0);
 }
 
+static inline struct page *page_cache_alloc_cold(struct address_space *x)
+{
+	return alloc_pages(x->gfp_mask|__GFP_COLD, 0);
+}
+
 typedef int filler_t(void *, struct page *);
 
 extern struct page * find_get_page(struct address_space *mapping,
diff -Nru a/mm/filemap.c b/mm/filemap.c
--- a/mm/filemap.c	Wed Oct 30 16:21:58 2002
+++ b/mm/filemap.c	Wed Oct 30 16:21:58 2002
@@ -258,7 +258,7 @@
 	struct page *page; 
 	int error;
 
-	page = page_cache_alloc(mapping);
+	page = page_cache_alloc_cold(mapping);
 	if (!page)
 		return -ENOMEM;
 
@@ -705,7 +705,7 @@
 		 * page..
 		 */
 		if (!cached_page) {
-			cached_page = page_cache_alloc(mapping);
+			cached_page = page_cache_alloc_cold(mapping);
 			if (!cached_page) {
 				desc->error = -ENOMEM;
 				break;
@@ -1199,7 +1199,7 @@
 	page = find_get_page(mapping, index);
 	if (!page) {
 		if (!cached_page) {
-			cached_page = page_cache_alloc(mapping);
+			cached_page = page_cache_alloc_cold(mapping);
 			if (!cached_page)
 				return ERR_PTR(-ENOMEM);
 		}
diff -Nru a/mm/readahead.c b/mm/readahead.c
--- a/mm/readahead.c	Wed Oct 30 16:21:58 2002
+++ b/mm/readahead.c	Wed Oct 30 16:21:58 2002
@@ -176,7 +176,7 @@
 			continue;
 
 		read_unlock(&mapping->page_lock);
-		page = page_cache_alloc(mapping);
+		page = page_cache_alloc_cold(mapping);
 		read_lock(&mapping->page_lock);
 		if (!page)
 			break;
-
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