Re: [PATCH 8/8] vmscan: Kick flusher threads to clean pages when reclaim is encountering dirty pages

Mel Gorman
2010-07-27T14:40:43Z

On Tue, Jul 27, 2010 at 10:34:23PM +0800, Wu Fengguang wrote:
> > If you plan to keep wakeup_flusher_threads(), a simpler form may be
> > sufficient, eg.
> >
> > laptop_mode ? 0 : (nr_dirty * 16)
>
> This number is not sensitive because the writeback code may well round
> it up to some more IO efficient value (currently 4MB). AFAIK the
> nr_pages parameters passed by all existing flusher callers are some
> rule-of-thumb value, and far from being an exact number.
>

I get that it's a rule of thumb but decided I would still pass in some value
related to nr_dirty that was bounded in some manner. Currently, that bound
is 4MB but maybe it should have been bound to MAX_WRITEBACK_PAGES (which is
4MB for x86, but could be anything depending on the base page size).

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