From: Wu Fengguang Introduce a new page flag: PG_readahead. It acts as a look-ahead mark, which tells the page reader: Hey, it's time to invoke the adaptive read-ahead logic! For the sake of I/O pipelining, don't wait until it runs out of cached pages. ;-) Signed-off-by: Wu Fengguang Signed-off-by: Andrew Morton --- include/linux/page-flags.h | 6 ++++++ mm/page_alloc.c | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-) diff -puN include/linux/page-flags.h~mm-introduce-pg_readahead include/linux/page-flags.h --- devel/include/linux/page-flags.h~mm-introduce-pg_readahead 2006-05-27 23:06:02.000000000 -0700 +++ devel-akpm/include/linux/page-flags.h 2006-05-27 23:06:02.000000000 -0700 @@ -90,6 +90,8 @@ #define PG_nosave_free 18 /* Free, should not be written */ #define PG_buddy 19 /* Page is free, on buddy lists */ +#define PG_readahead 20 /* Reminder to do readahead */ + #if (BITS_PER_LONG > 32) /* @@ -372,6 +374,10 @@ extern void __mod_page_state_offset(unsi #define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags) #define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags) +#define PageReadahead(page) test_bit(PG_readahead, &(page)->flags) +#define SetPageReadahead(page) set_bit(PG_readahead, &(page)->flags) +#define TestClearPageReadahead(page) test_and_clear_bit(PG_readahead, &(page)->flags) + struct page; /* forward declaration */ int test_clear_page_dirty(struct page *page); diff -puN mm/page_alloc.c~mm-introduce-pg_readahead mm/page_alloc.c --- devel/mm/page_alloc.c~mm-introduce-pg_readahead 2006-05-27 23:06:02.000000000 -0700 +++ devel-akpm/mm/page_alloc.c 2006-05-27 23:06:02.000000000 -0700 @@ -549,7 +549,7 @@ static int prep_new_page(struct page *pa if (PageReserved(page)) return 1; - page->flags &= ~(1 << PG_uptodate | 1 << PG_error | + page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_readahead | 1 << PG_referenced | 1 << PG_arch_1 | 1 << PG_checked | 1 << PG_mappedtodisk); set_page_private(page, 0); _