mm: pass readahead info down to the i/o scheduler
Some i/o schedulers (i.e. row-iosched, cfq-iosched) deploy an idling
algorithm in order to be better synced with the readahead algorithm.
Idling is a prediction algorithm for incoming read requests.
In this patch we mark pages which are part of a readahead window, by
setting a newly introduced flag. With this flag, the i/o scheduler can
identify a request which is associated with a readahead page. This
enables the i/o scheduler's idling mechanism to be en-sync with the
readahead mechanism and, in turn, can increase read throughput.
Change-Id: I0654f23315b6d19d71bcc9cc029c6b281a44b196
Signed-off-by: Lee Susman <lsusman@codeaurora.org>
diff --git a/mm/readahead.c b/mm/readahead.c
index 728a7a3..56f8a24 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -184,6 +184,9 @@
if (!page)
break;
page->index = page_offset;
+
+ page->flags |= (1L << PG_readahead);
+
list_add(&page->lru, &page_pool);
if (page_idx == nr_to_read - lookahead_size)
SetPageReadahead(page);