Messages in this thread | | | Date | Fri, 30 Sep 2005 22:41:48 -0400 | From | Bill Davidsen <> | Subject | Re: [PATCH 0/7] CART - an advanced page replacement policy |
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Peter Zijlstra wrote:
>On Thu, 2005-09-29 at 15:40 -0400, Bill Davidsen wrote: > > >>Peter Zijlstra wrote: >> >> >>>Multiple memory zone CART implementation for Linux. >>>An advanced page replacement policy. >>> >>>http://www.almaden.ibm.com/cs/people/dmodha/clockfast.pdf >>>(IBM does hold patent rights to the base algorithm ARC) >>> >>> >>Peter, this is a large patch, perhaps you could describe what configs >>benefit, >> >> > >All those that use swap. Those that exploit the weak side of LRU more >than others. > >CART is an adaptive algorithm that will act like LFU on one side and LRU >on the other, capturing both behaviours. Therefore it is also scan >proof, eg. 'use once' scans should not flush the full cache. > >Hence people with LFU friendly applications will see an improvement >while those who have an LRU friendly application should see no decrease >in swap performance. > >Non of the algorithms handle cyclic access very well, that is what patch >5 tries to tackle. > > > >>how much, >> >> > >In the cyclic case (n+a: a << n) I've seen speedups of over 300%. Other >cases much less. However I've yet to encounter a case where it gives >worse performance. > >I'm still constructing some corner case tests to give more hard numbers. > > > >>and what the right to use status of the patent might >>be. >> >> > >AFAIK IBM allows Linux implementation of their patents. >See: http://news.com.com/IBM+pledges+no+patent+attacks+against+Linux/2100-7344_3-5296787.html > > > >>In other words, why would a reader of LKML put in this patch and try it? >>The description of how it works is clear, but the problem solved isn't. >> >> > >I hope to have answered these questions. If any questions still remain, >please let me know. >
Thanks, you have cleared up all of the issues which I felt were unclear.
-- bill davidsen <davidsen@tmr.com> CTO TMR Associates, Inc Doing interesting things with small computers since 1979
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