Messages in this thread | | | Date | Wed, 20 Aug 2008 21:13:32 -0500 | From | Robin Holt <> | Subject | Re: [RFC][PATCH 0/2] Quicklist is slighly problematic. |
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On Wed, Aug 20, 2008 at 09:10:47AM -0500, Christoph Lameter wrote: > KOSAKI Motohiro wrote: > > Hi Cristoph, > > > > Thank you for explain your quicklist plan at OLS. > > > > So, I made summary to issue of quicklist. > > if you have a bit time, Could you please read this mail and patches? > > And, if possible, Could you please tell me your feeling? > > I believe what I said at the OLS was that quicklists are fundamentally crappy > and should be replaced by something that works (Guess that is what you meant > by "plan"?). Quicklists were generalized from the IA64 arch code. > > Good fixup but I would think that some more radical rework is needed. > > Maybe some of this needs to vanish into the TLB handling logic? > > Then I have thought for awhile that the main reason that quicklists exist are > the performance problems in the page allocator. If you can make the single > page alloc / free pass competitive in performance with quicklists then we > could get rid of all uses.
It is more than the free/alloc cycle, the quicklist saves us from having to zero the page. In a sparsely filled page table, it saves time and cache footprint. In a heavily used page table, you end up with a near wash.
One problem I see is somebody got rid of the node awareness. We used to not put pages onto a quicklist when they were being released from a different node than the cpu is on. Not sure where that went. It was done because of the trap page problem described here.
Thanks, Robin
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