Updates:
Summary: Array.shift() is "slow" (O(n)) for arrays in LO space
Comment #1 on issue 3059 by [email protected]: Array.shift() is "slow"
(O(n)) for arrays in LO space
http://code.google.com/p/v8/issues/detail?id=3059
The GC has nothing to do with this, and nothing is stalling either.
Array.shift() is an expensive operation, as it requires all array elements
to be moved. For most areas of the heap, V8 has implemented a special trick
to hide this cost: it simply bumps the pointer to the beginning of the
object by one, effectively cutting off the first element. However, when an
array is so large that it must be placed in "large object space", this
trick cannot be applied as object starts must be aligned, so on
every .shift() operation all elements must actually be moved in memory.
I'm not sure there's a whole lot we can do about this. If you want
a "Queue" object in JavaScript with guaranteed O(1) complexity
for .enqueue() and .dequeue() operations, you may want to implement your
own.
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