Re: [PATCH 1/7] vmscan: raise the bar to PAGEOUT_IO_SYNC stalls

From: Mel Gorman
Date: Thu Aug 05 2010 - 11:02:54 EST

On Thu, Aug 05, 2010 at 03:12:22PM +0900, KOSAKI Motohiro wrote:
> From: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> Fix "system goes unresponsive under memory pressure and lots of
> dirty/writeback pages" bug.
> In the above thread, Andreas Mohr described that
> Invoking any command locked up for minutes (note that I'm
> talking about attempted additional I/O to the _other_,
> _unaffected_ main system HDD - such as loading some shell
> binaries -, NOT the external SSD18M!!).
> This happens when the two conditions are both meet:
> - under memory pressure
> - writing heavily to a slow device
> <SNIP>

Other than an unnecessary whitespace removal at the end of the patch, I see
no problem with letting this patch stand on it's own as we are
reasonably sure this patch fixes a problem on its own. Patches 2-7 might
further improve the situation but can be considered as a new series.

This patch (as well as most of the series) will reject against current mmotm
because of other reclaim-related patches already in there. The resolutions
are not too hard but bear it in mind.

> <SNIP>

Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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