Since the VM_MAX_READAHEAD is greatly enlarged and the algorithm more
complex, it becomes necessary to insert some cond_resched() calls in
the read-ahead path.
If desktop users still feel audio jitters with the new read-ahead code,
please try one of the following ways to get rid of it:
1) compile kernel with CONFIG_PREEMPT_VOLUNTARY/CONFIG_PREEMPT
2) reduce the read-ahead request size by running
blockdev --setra 256 /dev/hda # or whatever device you are using
Signed-off-by: Wu Fengguang <[email protected]>
---
This patch is recommended by Con Kolivas to improve respond time for desktop.
Thanks!
fs/mpage.c | 4 +++-
mm/readahead.c | 9 +++++++--
2 files changed, 10 insertions(+), 3 deletions(-)
--- linux-2.6.17-rc4-mm3.orig/mm/readahead.c
+++ linux-2.6.17-rc4-mm3/mm/readahead.c
@@ -146,8 +146,10 @@ int read_cache_pages(struct address_spac
continue;
}
ret = filler(data, page);
- if (!pagevec_add(&lru_pvec, page))
+ if (!pagevec_add(&lru_pvec, page)) {
+ cond_resched();
__pagevec_lru_add(&lru_pvec);
+ }
if (ret) {
while (!list_empty(pages)) {
struct page *victim;
@@ -184,8 +186,10 @@ 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)) {
+ cond_resched();
__pagevec_lru_add(&lru_pvec);
+ }
} else
page_cache_release(page);
}
@@ -297,6 +301,7 @@ __do_page_cache_readahead(struct address
continue;
read_unlock_irq(&mapping->tree_lock);
+ cond_resched();
page = page_cache_alloc_cold(mapping);
read_lock_irq(&mapping->tree_lock);
if (!page)
--- linux-2.6.17-rc4-mm3.orig/fs/mpage.c
+++ linux-2.6.17-rc4-mm3/fs/mpage.c
@@ -407,8 +407,10 @@ mpage_readpages(struct address_space *ma
&last_block_in_bio, &map_bh,
&first_logical_block,
get_block);
- if (!pagevec_add(&lru_pvec, page))
+ if (!pagevec_add(&lru_pvec, page)) {
+ cond_resched();
__pagevec_lru_add(&lru_pvec);
+ }
} else {
page_cache_release(page);
}
--