Messages in this thread | | | Date | Tue, 26 Jul 2011 21:20:55 +1000 | From | Dave Chinner <> | Subject | Re: [RFC PATCH 0/8] Reduce filesystem writeback from page reclaim v2 |
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On Thu, Jul 21, 2011 at 05:28:42PM +0100, Mel Gorman wrote: > Warning: Long post with lots of figures. If you normally drink coffee > and you don't have a cup, get one or you may end up with a case of > keyboard face.
[snip]
> Overall, having kswapd avoiding writes does improve performance > which is not a surprise. Dave asked "do we even need IO at all from > reclaim?". On NUMA machines, the answer is "yes" unless the VM can > wake the flusher thread to clean a specific node.
Great answer, Mel. ;)
> When kswapd never > writes, processes can stall for significant periods of time waiting on > flushers to clean the correct pages. If all writing is to be deferred > to flushers, it must ensure that many writes on one node would not > starve requests for cleaning pages on another node.
Ok, so that's a direction we need to work towards, then.
> I'm currently of the opinion that we should consider merging patches > 1-7 and discuss what is required before merging. It can be tackled > later how the flushers can prioritise writing of pages belonging to > a particular zone before disabling all writes from reclaim.
Sounds reasonable to me.
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
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