RFR (S) JDK-8139922 Get rid of dead code in ConcurrentMark

Thomas Schatzl thomas.schatzl at oracle.com
Wed Nov 18 15:30:35 UTC 2015


On Wed, 2015-11-18 at 07:16 -0800, Jon Masamitsu wrote:
> On 11/18/2015 02:31 AM, Thomas Schatzl wrote:
> > Hi,
> >
> > On Tue, 2015-11-17 at 13:51 -0800, Jon Masamitsu wrote:
> >> Anyone think that parClear() is worth saving?  If just for
> >> symmetry with parMark()?
> >    I would prefer to remove unused code. The CMBitmap class does not feel
> > like being in any way reusable but a thin wrapper for use with G1
> > concurrent marking. This method would be simple to recreate too.
> Yes, it would be easy to recreate and I have no problem with
> removing it.  I actually was surprised that it was not being
> used.  I have a recollection that clearing the bit maps after
> a full GC on a gigantic heap was noticeable.  But if we need
> it, as you say, easily recreated.

  I think we do that in parallel without any synchronization on the
bitmap, splitting the whole bitmaps by region. Within the bitmap
corresponding to a single region, there is no kind of work stealing or

It would also be very costly to clear the whole bitmap bit by bit (which
is what the method does).


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