On 12/05/2014 21:28, Brandon Simmons wrote:
The idea is I'm using two atomic counters to coordinate concurrent
readers and writers along an "infinite array" (a linked list of array
segments that get allocated as needed and garbage collected as we go).
So currently each cell in each array is written to only once, with a
CAS.
Certainly you should freeze arrays when you're done writing to them,
this will help the GC a lot.
How large are your arrays? Perhaps the new small array type (in HEAD but not
7.8) would help?
Thanks, maybe so! The arrays can be any size, but probably not smaller
than length 64 (this will be static, at compile-time).
I read through https://ghc.haskell.org/trac/ghc/ticket/5925, and it
seems like the idea is to improve array creation. I'm pretty happy
with the speed of cloning an array (but maybe cloneSmallArray will be
even faster still).
It also looks like stg_casSmallArrayzh (in PrimOps.cmm) omits the card
marking (maybe the idea is if the array is already at ~128 elements or
less, then the card-marking is all just overhead?).
That right, the cards currently cover 128 elements, and there's also a
per-array dirty bit, so the card table in an array smaller than 128 elts
is just overhead.
Cheers,
Simon
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