Hi Johannes!
On Fri, Sep 30, 2011 at 10:17 AM, Johannes Weiner <jweiner@xxxxxxxxxx> wrote:
> But there is a flaw in that we have a zoned page allocator which does
> not care about the global state but rather the state of individual
> memory zones. And right now there is nothing that prevents one zone
> from filling up with dirty pages while other zones are spared, which
> frequently leads to situations where kswapd, in order to restore the
> watermark of free pages, does indeed have to write pages from that
> zone's LRU list. This can interfere so badly with IO from the flusher
> threads that major filesystems (btrfs, xfs, ext4) mostly ignore write
> requests from reclaim already, taking away the VM's only possibility
> to keep such a zone balanced, aside from hoping the flushers will soon
> clean pages from that zone.
The obvious question is: how did you test this? Can you share the results?
Pekka
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