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 <lsusman@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>
diff --git a/mm/readahead.c b/mm/readahead.c
index c8a955b..7dc48ba 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -233,6 +233,8 @@
/*
* Set the initial window size, round to next power of 2 and square
+ * Small size is not dependent 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
@@ -241,7 +243,7 @@
{
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;