This relays all ASYNC file writeback IOs to the flusher threads.
The lesser SYNC pageout()s will work as before (as a last resort).
It's a minimal prototype implementation and barely runs without panic.
It potentially requires lots of more work to go stable.
TODO: avoid OOM if the LRU list is small and/or the storage is slow, so
that the flusher cannot clean enough pages before the LRU is full
scanned. One simple way could be to do waits on dirty/writeback pages
when priority < 3 for even order 0 allocations.
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
mm/page-writeback.c | 2 +-
mm/vmscan.c | 13 +++++++++++++
2 files changed, 14 insertions(+), 1 deletion(-)
--- linux-next.orig/mm/vmscan.c 2010-09-13 19:48:16.000000000 +0800
+++ linux-next/mm/vmscan.c 2010-09-13 20:14:42.000000000 +0800
@@ -756,6 +756,19 @@ static unsigned long shrink_page_list(st
}
}
+ if (page_is_file_cache(page) && mapping &&
+ sync_writeback == PAGEOUT_IO_ASYNC) {
+ if (!bdi_start_inode_writeback(
+ mapping->backing_dev_info,
+ mapping->host, page_index(page))) {
+ SetPageReclaim(page);
+ goto keep_locked;
+ } else if (!current_is_kswapd() &&
+ printk_ratelimit()) {
+ printk(KERN_INFO "cannot pageout\n");
+ }
+ }
+
if (references == PAGEREF_RECLAIM_CLEAN)
goto keep_locked;
if (!may_enter_fs)
--- linux-next.orig/mm/page-writeback.c 2010-09-13 19:48:16.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-09-13 20:06:26.000000000 +0800
@@ -1232,6 +1232,7 @@ int set_page_dirty(struct page *page)
{
struct address_space *mapping = page_mapping(page);
+ ClearPageReclaim(page);
if (likely(mapping)) {
int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
#ifdef CONFIG_BLOCK
@@ -1289,7 +1290,6 @@ int clear_page_dirty_for_io(struct page
BUG_ON(!PageLocked(page));
- ClearPageReclaim(page);
if (mapping && mapping_cap_account_dirty(mapping)) {
/*
* Yes, Virginia, this is indeed insane.
--
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