On Thu, May 05, 2011 at 05:24:27AM +0800, Jan Kara wrote:
> On Mon 02-05-11 11:17:53, Wu Fengguang wrote:
> > This removes writeback_control.wb_start and does more straightforward
> > sync livelock prevention by setting .older_than_this to prevent extra
> > inodes from being enqueued in the first place.
> >
> > --- linux-next.orig/fs/fs-writeback.c 2011-05-02 11:17:24.000000000 +0800
> > +++ linux-next/fs/fs-writeback.c 2011-05-02 11:17:27.000000000 +0800
> > @@ -683,10 +672,12 @@ static long wb_writeback(struct bdi_writ
> > * (quickly) tag currently dirty pages
> > * (maybe slowly) sync all tagged pages
> > */
> > - if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_sync)
> > + if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_sync) {
> > write_chunk = LONG_MAX;
> > + oldest_jif = jiffies;
> > + wbc.older_than_this = &oldest_jif;
> > + }
> What are the implications of not doing dirty-time livelock avoidance for
> other types of writeback? Is that a mistake? I'd prefer to have in
> wb_writeback():
> if (wbc.for_kupdate)
> oldest_jif = jiffies - msecs_to_jiffies(dirty_expire_interval * 10);
> else
> oldest_jif = jiffies;
> wbc.older_than_this = &oldest_jif;
>
> And when you have this, you can make wbc.older_than_this just a plain
> number and remove all those checks for wbc.older_than_this == NULL.
Good point. Here is the fixed patch. Will you send the patch to change
the type when the current patches are settled down?
Thanks,
Fengguang
---
Subject: writeback: avoid extra sync work at enqueue time
Date: Sat Apr 23 11:26:07 CST 2011
This removes writeback_control.wb_start and does more straightforward
sync livelock prevention by setting .older_than_this to prevent extra
inodes from being enqueued in the first place.
CC: Jan Kara <jack@xxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
fs/fs-writeback.c | 16 +++-------------
include/linux/writeback.h | 3 ---
2 files changed, 3 insertions(+), 16 deletions(-)
--- linux-next.orig/fs/fs-writeback.c 2011-05-04 20:19:20.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2011-05-05 13:15:42.000000000 +0800
@@ -544,15 +544,6 @@ static int writeback_sb_inodes(struct su
continue;
}
- /*
- * Was this inode dirtied after sync_sb_inodes was called?
- * This keeps sync from extra jobs and livelock.
- */
- if (inode_dirtied_after(inode, wbc->wb_start)) {
- spin_unlock(&inode->i_lock);
- return 1;
- }
-
__iget(inode);
pages_skipped = wbc->pages_skipped;
@@ -585,9 +576,6 @@ static void __writeback_inodes_wb(struct
{
int ret = 0;
- if (!wbc->wb_start)
- wbc->wb_start = jiffies; /* livelock avoidance */
-
while (!list_empty(&wb->b_io)) {
struct inode *inode = wb_inode(wb->b_io.prev);
struct super_block *sb = inode->i_sb;
@@ -686,7 +674,9 @@ static long wb_writeback(struct bdi_writ
if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_sync)
write_chunk = LONG_MAX;
- wbc.wb_start = jiffies; /* livelock avoidance */
+ oldest_jif = jiffies;
+ wbc.older_than_this = &oldest_jif;
+
for (;;) {
/*
* Stop writeback when nr_pages has been consumed
--- linux-next.orig/include/linux/writeback.h 2011-05-04 20:19:20.000000000 +0800
+++ linux-next/include/linux/writeback.h 2011-05-05 13:14:53.000000000 +0800
@@ -26,9 +26,6 @@ struct writeback_control {
enum writeback_sync_modes sync_mode;
unsigned long *older_than_this; /* If !NULL, only write back inodes
older than this */
- unsigned long wb_start; /* Time writeback_inodes_wb was
- called. This is needed to avoid
- extra jobs and livelock */
long nr_to_write; /* Write this many pages, and decrement
this for each page written */
long pages_skipped; /* Pages which were not written */
--
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