Re: Potential GSoC proposal: Reduce the speed gap between 'ghc -c' and 'ghc --make'

wrote:

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Thanks. I'll look into how to optimise .hi loading by more traditional means, then.

Lennart is working on speeding up the binary package (which I believe is used to decode the .hi files.) His work might benefit this effort.

Last time I tested it, mmap still offered better performance than fread on linux. In addition to improving the deserialization code it would seem like a good idea to mmap the whole file at the outset as well. It seems like readBinMem is the relevant function (readIFace -> readBinIFace -> readBinMem), which occurs here: https://github.com/ghc/ghc/blob/08894f96407635781a233145435a78f144accab0/com... Currently it does one big hGetBuf to read the file. Since the interface files aren't changing dynamically, I think it's safe to just replace this code with an mmap. It's nice to see that we have several wrapped versions of mmap provided on hackage: http://hackage.haskell.org/package/vector-mmap http://hackage.haskell.org/package/bytestring-mmap-0.2.2 http://hackage.haskell.org/package/mmap-0.5.7 Cheers, -Ryan