Messages in this thread | | | Date | Wed, 29 May 2013 12:53:56 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 4/4] mm: vmscan: Take page buffers dirty and locked state into account |
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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.
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