[PATCH 16/16] io: reduce lantency

[Wu Fengguang <wfg@mail.ustc.edu.cn>]

[-- Attachment #1: io-low-delay.patch --]
[-- Type: text/plain, Size: 1490 bytes --]

This is recommended by Con Kolivas to improve respond time for desktop.

Since the VM_MAX_READAHEAD is greatly enlarged, it may be necessary to insert
some cond_resched() calls. Correct me, I'm not quite sure about the effects.

Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---


 fs/mpage.c     |    4 +++-
 mm/readahead.c |    5 ++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

--- linux-2.6.14-mm1.orig/mm/readahead.c
+++ linux-2.6.14-mm1/mm/readahead.c
@@ -582,8 +582,10 @@ static int read_pages(struct address_spa
 		if (!add_to_page_cache(page, mapping,
 					page->index, GFP_KERNEL)) {
 			mapping->a_ops->readpage(filp, page);
-			if (!pagevec_add(&lru_pvec, page))
+			if (!pagevec_add(&lru_pvec, page)) {
 				__pagevec_lru_add(&lru_pvec);
+				cond_resched();
+			}
 		} else {
 			page_cache_release(page);
 		}
@@ -701,6 +703,7 @@ __do_page_cache_readahead(struct address
 		}
 
 		read_unlock_irq(&mapping->tree_lock);
+		cond_resched();
 		page = page_cache_alloc_cold(mapping);
 		read_lock_irq(&mapping->tree_lock);
 		if (!page)
--- linux-2.6.14-mm1.orig/fs/mpage.c
+++ linux-2.6.14-mm1/fs/mpage.c
@@ -343,8 +343,10 @@ mpage_readpages(struct address_space *ma
 			bio = do_mpage_readpage(bio, page,
 					nr_pages - page_idx,
 					&last_block_in_bio, get_block);
-			if (!pagevec_add(&lru_pvec, page))
+			if (!pagevec_add(&lru_pvec, page)) {
 				__pagevec_lru_add(&lru_pvec);
+				cond_resched();
+			}
 		} else {
 			page_cache_release(page);
 		}

--