exit loop in balance_dirty_pages when no more pages available to write
On a bdi that has very little traffic balance_dirty_pages can loop
needlessly waiting until do_writepages has written enough pages.
do_writepages will return encountered_congestion==0 && nr_to_write > 0
when it has completed a pass but did not find enough pages available to
write. balance_dirty_pages ignores this and keeps looping until a total
of chunk pages was written.
this patch adds an extra exit condition to break out of the loop in this
case.
I've tested this on my amd64 desktop, and I also have a version of this
patch that includes a printk and a test case that occasionally does
trigger this condition.
Signed-off-by: Richard Kennedy <[EMAIL PROTECTED]>
------
--- linux-2.6.22.1/mm/page-writeback.c.orig 2007-07-30 16:36:09.000000000
+0100
+++ linux-2.6.22.1/mm/page-writeback.c 2007-07-31 16:26:43.000000000 +0100
@@ -250,6 +250,8 @@ static void balance_dirty_pages(struct a
pages_written += write_chunk - wbc.nr_to_write;
if (pages_written >= write_chunk)
break; /* We've done our duty */
+ if (!wbc.encountered_congestion && wbc.nr_to_write > 0)
+ break; /* didn't find enough to do */
}
congestion_wait(WRITE, HZ/10);
}
-
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