Re: [PATCH 4/4] mm: vmscan: Take page buffers dirty and locked state into account

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 27 May 2013 14:02:58 +0100 Mel Gorman <mgorman@suse.de> wrote:

> Page reclaim keeps track of dirty and under writeback pages and uses it to
> determine if wait_iff_congested() should stall or if kswapd should begin
> writing back pages. This fails to account for buffer pages that can be under
> writeback but not PageWriteback which is the case for filesystems like ext3
> ordered mode. Furthermore, PageDirty buffer pages can have all the buffers
> clean and writepage does no IO so it should not be accounted as congested.

iirc, the PageDirty-all-buffers-clean state is pretty rare.  It might
not be worth bothering about?

> This patch adds an address_space operation that filesystems may
> optionally use to check if a page is really dirty or really under
> writeback.

address_space_operations methods are Documented in
Documentation/filesystems/vfs.txt ;)

> An implementation is provided for for buffer_heads is added
> and used for block operations and ext3 in ordered mode. By default the
> page flags are obeyed.
> 
> Credit goes to Jan Kara for identifying that the page flags alone are
> not sufficient for ext3 and sanity checking a number of ideas on how
> the problem could be addressed.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>