Messages in this thread | | | Subject | Re: [RFC][PATCH] split file and anonymous page queues #2 | From | Lee Schermerhorn <> | Date | Tue, 20 Mar 2007 12:24:57 -0400 |
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On Mon, 2007-03-19 at 20:52 -0400, Rik van Riel wrote: > Split the anonymous and file backed pages out onto their own pageout > queues. This we do not unnecessarily churn through lots of anonymous > pages when we do not want to swap them out anyway. > > This should (with additional tuning) be a great step forward in > scalability, allowing Linux to run well on very large systems where > scanning through the anonymous memory (on our way to the page cache > memory we do want to evict) is slowing systems down significantly. > > This patch has been stress tested and seems to work, but has not > been fine tuned or benchmarked yet. For now the swappiness parameter > can be used to tweak swap aggressiveness up and down as desired, but > in the long run we may want to simply measure IO cost of page cache > and anonymous memory and auto-adjust. > > We apply pressure to each of sets of the pageout queues based on: > - the size of each queue > - the fraction of recently referenced pages in each queue, > not counting used-once file pages > - swappiness (file IO is more efficient than swap IO) > > Please take this patch for a spin and let me know what goes well > and what goes wrong.
Rick: Which tree is the patch against. Diffs say 2.6.20.x86_64, but doesn't apply to 2.6.20 which doesn't use __inc_zone_state() for things like nr_active, nr_inactive, ...
Also, in the snippet:
>--- linux-2.6.20.x86_64/mm/swap_state.c.vmsplit 2007-02-04 >13:44:54.000000000 -0500 >+++ linux-2.6.20.x86_64/mm/swap_state.c 2007-03-19 12:00:23.000000000 -0400 >@@ -354,7 +354,7 @@ struct page *read_swap_cache_async(swp_e > /* > * Initiate read into locked page and return. > */ >- lru_cache_add_active(new_page); >+ lru_cache_add_anon(new_page); > swap_readpage(NULL, new_page); > return new_page; > }
Should that be lru_cache_add_active_anon()? Or did you intend to add it to the inactive anon list?
Finally, could you [should you?] skip scanning the anon lists--or at least the inactive anon list--when nr_swap_pages == 0? The anon pages aren't going anywhere, right? I think this would obviate Christoph L's patch to exclude anon pages from the LRU when there is no swap.
Lee
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