Re: [PATCH] mm/filemap.c: unconditionally call mark_page_accessed

[Nick Piggin <npiggin@suse.de>]

On Thu, Mar 15, 2007 at 11:56:59AM -0400, Chuck Ebbert wrote:
> Ashif Harji wrote:
> > 
> > This patch unconditionally calls mark_page_accessed to prevent pages,
> > especially for small files, from being evicted from the page cache
> > despite frequent access.
> > 
> > Signed-off-by: Ashif Harji <asharji@beta.uwaterloo.ca>
> > 
> 
> I like mine better -- it leaves the comment:

How about this? It also doesn't break the use-once heuristic.

--
A change to make database style random read() workloads perform better, by
calling mark_page_accessed for some non-page-aligned reads broke the case of
< PAGE_CACHE_SIZE files, which will not get their prev_index moved past the
first page.

Combine both heuristics for marking the page accessed.

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c
+++ linux-2.6/mm/filemap.c
@@ -929,7 +929,7 @@ page_ok:
 		 * When (part of) the same page is read multiple times
 		 * in succession, only mark it as accessed the first time.
 		 */
-		if (prev_index != index)
+		if (prev_index != index || !offset)
 			mark_page_accessed(page);
 		prev_index = index;