Request for reviews (M): 7059037: Use BIS for zeroing on T4

[Ramki Ramakrishna]

Hi Vladimir --

On 8/24/2011 5:52 PM, Vladimir Kozlov wrote:
> http://cr.openjdk.java.net/~kvn/7059037/webrev
>
> 7059037: Use BIS for zeroing on T4
>
...
> Zap new object in CollectedHeap::allocate_from_tlab_slow() instead of 
> zeroing it
> since it will be cleaned later in init_obj().
> Fixed call sites of check_for_bad_heap_word_value() where klass is not
> initialized to avoid the verification failure.
>

Can you describe why these two changes were necessary? There was already 
support
for skipping headers for concurrent GC's when zapping and verifying. Did 
something
change that caused this to be changed.

I haven't looked at the rest of the files, but a high level description 
of the need to
make this change would allow me to review the changes that necessitated 
this,
and whether it could not be done more easily otherwise (using the existing
framework of skipping a preamble of words in the object).

-- ramki