[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.

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 1fe640eaf601f6816b08808da887d581957cb732..d2e647ac9623bada1821f6d7d0a42a08246c1eb7 100644 (file)
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -31,6 +31,11 @@ static inline struct page *page_cache_alloc(struct address_space *x)
        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 --git a/mm/filemap.c b/mm/filemap.c
index 5cc2c080c33148915c3c80ed1696cedc6360446d..af26d617f922607a6a0e257e02d4dc9f7ee2453a 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -258,7 +258,7 @@ static int page_cache_read(struct file * file, unsigned long offset)
        struct page *page; 
        int error;
 
-       page = page_cache_alloc(mapping);
+       page = page_cache_alloc_cold(mapping);
        if (!page)
                return -ENOMEM;
 
@@ -705,7 +705,7 @@ no_cached_page:
                 * 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 @@ repeat:
        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 --git a/mm/readahead.c b/mm/readahead.c
index 0ab09031edebdd972f3ce646773208725e12582e..6174f412e6e89c675f2b8edcb97d6221ef7952d1 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -176,7 +176,7 @@ int do_page_cache_readahead(struct address_space *mapping,
                        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;