Messages in this thread | | | Date | Wed, 30 Mar 2005 23:18:01 -0800 | From | Andrew Morton <> | Subject | Re: NFS client latencies |
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Ingo Molnar <mingo@elte.hu> wrote: > > > * Trond Myklebust <trond.myklebust@fys.uio.no> wrote: > > > > The 7 ms are spent in this loop: > > > > Which is basically confirming what the guys from Bull already told me, > > namely that the radix tree tag stuff is much less efficient that what > > we've got now. I never saw their patches, though, so I was curious to > > try it for myself. > > i think the numbers are being misinterpreted. I believe this patch is a > big step forward. The big thing is that nfs_list_add_request() is O(1) > now - while _a single request addition to the sorted list_ triggered the > 1+ msec latency in Lee's previous trace.
Well. The radix-tree approach's best-case is probably quite a lot worse than the list-based approach's best-case. It hits a lot more cachelines and involves a lot more code.
But of course the radix-tree's worst-case will be far better than list's.
And presumably that list-based code rarely hits the worst-case, else it would have been changed by now.
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