Messages in this thread | | | Date | Sat, 31 May 2003 13:07:43 +0200 | From | Jörn Engel <> | Subject | Re: [PATCH RFC] 1/2 central workspace for zlib |
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On Sat, 31 May 2003 20:51:04 +1000, James Morris wrote: > On Fri, 30 May 2003, David S. Miller wrote: > > > My understanding is that these are just scratchpads. The contents > > while a decompress/compress operation is not occuring does not > > matter. > > It depends on how the zlib library is used. The filesystems and crypto > code use it so that each operation is distinct, although it is possible to > maintain compression history between operations: PPP does this via a > sliding compression window, and there are other potential users such as > ROHC. > > One way of addressing this would to allow the user to supply their own > workspace if compression history needs to be maintained.
Agreed. How much memory is needed for the history? Most of the workspace or substancially less?
> > So if we have 2 such scratchpads per cpu, one for normal and one for > > BH context, his idea truly can work and be useful to everyone. > > It would also be lockless on SMP. > > And perhaps implement with a lazy allocation scheme so that these > scratchpads are only allocated if needed (i.e. a caller does not provide > its own workspace).
Disagreed. Two scratchpads per cpu won't hurt in the mean case much and lazy allocation wouldn't improve the worst case either. Keep them static and simple.
Jörn
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