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

[Chuck Ebbert <cebbert@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 301 bytes --]

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:



[-- Attachment #2: linux-2.6-fix_mark_page_accessed.patch --]
[-- Type: text/plain, Size: 1080 bytes --]

From: Chuck Ebbert <cebbert@redhat.com>

Always mark page as accessed when reading multiple times.
Original idea and patch by Ashif Harji <asharji@cs.uwaterloo.ca>

Signed-off-by: Chuck Ebbert <cebbert@redhat.com>

--- 2.6.20.2-t.orig/mm/filemap.c
+++ 2.6.20.2-t/mm/filemap.c
@@ -887,7 +887,6 @@
 	unsigned long offset;
 	unsigned long last_index;
 	unsigned long next_index;
-	unsigned long prev_index;
 	loff_t isize;
 	struct page *cached_page;
 	int error;
@@ -896,7 +895,6 @@
 	cached_page = NULL;
 	index = *ppos >> PAGE_CACHE_SHIFT;
 	next_index = index;
-	prev_index = ra.prev_page;
 	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 	offset = *ppos & ~PAGE_CACHE_MASK;
 
@@ -945,11 +943,9 @@
 
 		/*
 		 * When (part of) the same page is read multiple times
-		 * in succession, only mark it as accessed the first time.
+		 * in succession, always mark it accessed.
 		 */
-		if (prev_index != index)
-			mark_page_accessed(page);
-		prev_index = index;
+		mark_page_accessed(page);
 
 		/*
 		 * Ok, we have the page, and it's up-to-date, so