--- mm/readahead.c

+++ mm/readahead.c

@@ -17,6 +17,7 @@

#include <linux/task_io_accounting_ops.h>

#include <linux/pagevec.h>

#include <linux/pagemap.h>

+#include <linux/swap.h>

/*

* Initialise a struct file's readahead state. Assumes that the caller has

@@ -107,7 +108,7 @@ int read_cache_pages(struct address_spac

EXPORT_SYMBOL(read_cache_pages);

static int read_pages(struct address_space *mapping, struct file *filp,

- struct list_head *pages, unsigned nr_pages)

+ struct list_head *pages, unsigned nr_pages, int tail)

{

struct blk_plug plug;

unsigned page_idx;

@@ -125,8 +126,8 @@ static int read_pages(struct address_spa

for (page_idx = 0; page_idx < nr_pages; page_idx++) {

struct page *page = list_to_page(pages);

list_del(&page->lru);

- if (!add_to_page_cache_lru(page, mapping,

- page->index, GFP_KERNEL)) {

+ if (!__add_to_page_cache_lru(page, mapping,

+ page->index, GFP_KERNEL, tail)) {

mapping->a_ops->readpage(filp, page);

}

page_cache_release(page);

@@ -139,6 +140,28 @@ out:

return ret;

}

+static inline int nr_mapped(void)

+{

+ return global_page_state(NR_FILE_MAPPED) +

+ global_page_state(NR_ANON_PAGES);

+}

+

+/*

+ * This examines how large in pages a file size is and returns 1 if it is

+ * more than half the unmapped ram. Avoid doing read_page_state which is

+ * expensive unless we already know it is likely to be large enough.

+ */

+static int large_isize(unsigned long nr_pages)

+{

+ if (nr_pages * 6 > vm_total_pages) {

+ unsigned long unmapped_ram = vm_total_pages - nr_mapped();

+

+ if (nr_pages * 2 > unmapped_ram)

+ return 1;

+ }

+ return 0;

+}

+

/*

* __do_page_cache_readahead() actually reads a chunk of disk. It allocates all

* the pages first, then submits them all for I/O. This avoids the very bad

@@ -196,7 +219,8 @@ __do_page_cache_readahead(struct address

* will then handle the error.

*/

if (ret)

- read_pages(mapping, filp, &page_pool, ret);

+ read_pages(mapping, filp, &page_pool, ret,

+ large_isize(end_index));

BUG_ON(!list_empty(&page_pool));

out:

return ret;