Messages in this thread | | | Date | Fri, 1 Feb 2002 10:12:42 +1100 | From | Anton Blanchard <> | Subject | Re: [PATCH] Radix-tree pagecache for 2.5 |
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Hi Ingo,
> Yes, it's very nice. Anton Blanchard has benchmarked both patch variants > (tree vs. scalable-hash page buckets) for SMP scalability against the > stock hash, on big RAM, many CPUs boxes, via dbench load. He has found > performance of radix trees vs. scalable hash to be at least equivalent. (i > think Anton has a few links to show the resulting graphs.)
Here are some results on a 12 way machine. (2.4.16-splay is the radix patch):
http://samba.org/~anton/linux/pagecache_locking/1/summary.png
As you can see both patches give pretty much equal improvements.
The other problem with the current pagecache hash is that it maxes out at order 9 (due to the get_free_pages limitation) which starts to hurt at 4GB RAM and above. On a 32GB machine the average hashchain depth was very high:
http://samba.org/~anton/linux/pagecache/pagecache_before.png
There were a few solutions (from davem and ingo) to allocate a larger hash but with the radix patch we no longer have to worry about this.
So the radix patch solves 2 problems quite nicely :)
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