Re: It's time for 5.0.1

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

On Dec 12,  9:56am, Peter Stephenson wrote:
}
} On Wed, 12 Dec 2012 00:14:11 -0800
} Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx> wrote:
} > The problem with this is that the better zhalloc() is at filling up
} > the Heap arenas, the harder freeheap() has to work -- because it ends
} > up managing a Heapstack for each of a bunch of useless [that is,
} > full] Heap arenas.  At that point it'd be much better if it just
} > pushed the entire heaps list and started over from scratch.
} 
} One point about the above is that if we keep the heap size small, 16384
} instead of ~ 10 times as much

Regarding that ... there are some comments in zsh.h that make it appear
we should stick with multiples of 8, so 131072 or 262144 if we were in
fact to make it "about 10" times bigger.

} it's much less wasteful to forget about
} heapstacks altogether and simply mark the current heap and start a new
} one when you push.  Then you just have the one linked list and
} everything stays linear.

Well, there are still two linked lists: the currently growing heap and
the stack of pushed heaps.  I think we can do away with the Heapstack
struct and use the heapstack pointer in the Heap struct to manage the
pushed heaps.

} I think wasting something of order 16 kB each
} time we push (and getting it back when we pop) is probably neither here
} nor there these days.

Well ... in a pathological case (lots of allocations of 8k+1 bytes) you
might be wasting as much space as was already in use.  But you could
construct a similar pathological case for the current algorithm, so I
don't think it's worth solving right now.

} I'm not 100% sure what's going on with switch_heaps(), but you might
} hope it was agnostic about the underlying heap implementation.

I briefly considered NEWHEAP/OLDHEAP or SWITCHHEAPS/SWITCHBACKHEAPS as
a stand-in for pushheap/popheap in selected contexts, but concluded
that I don't understand well enough to initialize them ... nor do I
recall why the completion system is using them, except that it seems
to have something to do with completion-specific special parameters.

But I don't think they fiddle with how push/free/pop work underneath.