In this vein, you may be interested in trying out the unix-bytestring package (it contains ByteString based bindings for POSIX I/O - but you'll still need the unix package to get at the underlying file descriptor.)
http://hackage.haskell.org/packages/archive/unix-bytestring/0.3.5.4/doc/html/System-Posix-IO-ByteString.html On Mon, Aug 27, 2012 at 3:48 PM, Johan Tibell <johan.tib...@gmail.com> wrote: > On Mon, Aug 27, 2012 at 1:43 PM, J Baptist <arc38...@hotmail.com> wrote: >> I'm looking into high-performance I/O, particularly on a tmpfs (in-memory) >> filesystem. This involves creating lots of little files. Unfortunately, it >> seems that Haskell's performance in this area is not comparable to that of >> C. I assume that this is because of the overhead involved in opening and >> closing files. Some cursory profiling confirmed this: most of the runtime of >> the program is in taken by openFile, hPutStr, and hClose. >> >> I thought that it might be faster to call the C library functions exposed as >> foreign imports in System.Posix.Internals, and thereby cut out some of >> Haskell's overhead. This indeed improved performance, but the program is >> still nearly twice as slow as the corresponding C program. >> >> I took some benchmarks. I wrote a program to create 500.000 files on a tmpfs >> filesystem, and write an integer into each of them. I did this in C, using >> the open; and twice in Haskell, using openFile and c_open. Here are the >> results: >> >> C program, using open and friends (gcc 4.4.3) >> real 0m4.614s >> user 0m0.380s >> sys 0m4.200s >> >> Haskell, using System.IO.openFile and friends (ghc 7.4.2) >> real 0m14.892s >> user 0m7.700s >> sys 0m6.890s >> >> Haskell, using System.Posix.Internals.c_open and friends (ghc 7.4.2) >> real 0m7.372s >> user 0m2.390s >> sys 0m4.570s >> >> Why question is: why is this so slow? Could the culprit be the marshaling >> necessary to pass the parameters to the foreign functions? If I'm calling >> the low-level function c_open anyway, shouldn't performance be closer to C? >> Does anyone have suggestions for how to improve this? >> >> If anyone is interested, I can provide the code I used for these benchmarks. > > Please do. You can paste them at http://hpaste.org/ > > Could you try using the Data.ByteString API. I don't have the code in > front of me so I don't know if the System.Posix API uses Strings. If > it does, that's most likely the issue. > > -- Johan > > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users@haskell.org > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users -- Regards, Austin _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
