mm: change initial readahead window size calculation

Change the logic which determines the initial readahead window size such that for small requests (one page) the initial window size will be x4 the size of the original request, regardless of the VM_MAX_READAHEAD value. This prevents a rapid ramp-up that could be caused due to increasing VM_MAX_READAHEAD. Change-Id: I93d59c515d7e6c6d62348790980ff7bd4f434997 Signed-off-by: Lee Susman <[email protected]>
CyanogenMod · Apr 8, 2013 · 7893b2e · 7893b2e
1 parent 9a87969
commit 7893b2e
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/mm/readahead.c b/mm/readahead.c
@@ -261,6 +261,8 @@ unsigned long ra_submit(struct file_ra_state *ra,
 
 /*
  * Set the initial window size, round to next power of 2 and square
+ * Small size is not dependant on max value - only a one-page read is regarded
+ * as small.
  * for small size, x 4 for medium, and x 2 for large
  * for 128k (32 page) max ra
  * 1-8 page = 32k initial, > 8 page = 128k initial
@@ -269,7 +271,7 @@ static unsigned long get_init_ra_size(unsigned long size, unsigned long max)
 {
 	unsigned long newsize = roundup_pow_of_two(size);
 
-	if (newsize <= max / 32)
+	if (newsize <= 1)
 		newsize = newsize * 4;
 	else if (newsize <= max / 4)
 		newsize = newsize * 2;