Shrink dictionaries on deletion if number of elements are less than a

Shrink dictionaries on deletion if number of elements are less than a
quarter of the capacity.

R=vegorov@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=8391

[Vyacheslav Egorov (Chromium), 2011-06-22 14:39:36]

LGTM with the comment addressed.

http://codereview.chromium.org/7190032/diff/1/src/objects.cc
File src/objects.cc (right):

http://codereview.chromium.org/7190032/diff/1/src/objects.cc#newcode10052
src/objects.cc:10052: if (new_capacity < 16) return this;
This is a bit strange. 

I would ensure that (new_capacity >= 2 * nof) otherwise will get another
rehashing immediately when we try to add a new element after Shrink'ing. Also
not very good for conflicts.

[Mads Ager (chromium), 2011-06-22 14:55:20]

Thanks Slava!

http://codereview.chromium.org/7190032/diff/1/src/objects.cc
File src/objects.cc (right):

http://codereview.chromium.org/7190032/diff/1/src/objects.cc#newcode10052
src/objects.cc:10052: if (new_capacity < 16) return this;
On 2011/06/22 14:39:36, Vyacheslav Egorov wrote:
> This is a bit strange. 
> 
> I would ensure that (new_capacity >= 2 * nof) otherwise will get another
> rehashing immediately when we try to add a new element after Shrink'ing. Also
> not very good for conflicts.

Ah, I actually mean this. However, I did not mean new_capacity to be capacity >>
2. I meant it to be capacity >> 1. Since nof can be zero I want to make sure
that we do not go below 16.