[project @ 2006-01-17 16:03:47 by simonmar]
Improve the GC behaviour of IOArrays/STArrays See Ticket #650 This is a small change to the way mutable arrays interact with the GC, that can have a dramatic effect on performance, and make tricks with unsafeThaw/unsafeFreeze redundant. Data.HashTable should be faster now (I haven't measured it yet). We now have two mutable array closure types, MUT_ARR_PTRS_CLEAN and MUT_ARR_PTRS_DIRTY. Both are on the mutable list if the array is in an old generation. writeArray# sets the type to MUT_ARR_PTRS_DIRTY. The garbage collector can set the type to MUT_ARR_PTRS_CLEAN if it finds that no element of the array points into a younger generation (discovering this required a small addition to evacuate(), but rough tests indicate that it doesn't measurably affect performance). NOTE: none of this affects unboxed arrays (IOUArray/STUArray), only boxed arrays (IOArray/STArray). We could go further and extend the DIRTY bit to be per-block rather than for the whole array, but for now this is an easy improvement.
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