Request for reviews (M): 7013538: Java memory leak with escape analysis

[Tom Rodriguez]

Any reason not to completely replace VectorSetI with your new implementation?  Otherwise I think it's ok.

tom

On Feb 4, 2011, at 11:38 AM, Vladimir Kozlov wrote:

> http://cr.openjdk.java.net/~kvn/7013538/webrev
> 
> Fixed 7013538: Java memory leak with escape analysis
> 
> First, it is not leak. I instrumented VM around method
> compilation call to see if there are allocations which
> are not freed. There are none. I used mechanism similar
> to NoHandleMark to catch direct calls to os::malloc()
> (NoMallocMark). I found only one case (see below) but it
> frees memory almost immediately. The rest (major part) of
> allocations happened on thread Resource area and Compile
> arena which return used Chunks to ChunkPool after each
> compilation. But ChunkPool could become very large with EA.
> It is cleaned each 5 sec by VM task but there could be
> situations when 2 compilers threads request a lot of
> memory during 5 sec period causing out of memory problems.
> 
> So the problem is compilation with EA consumes C heap a lot
> more than without it. Collected allocation statistics during
> one hour of the test run (dacapo is running eclipse several
> times) shows that used C Heap size with EA is around 500Mb
> when without EA it is only 150Mb (not all of it is used,
> it could be fragmented because of the problem 2 below).
> Also numbers of calls to os::malloc rises from 2.5 millions
> to 10.5 M.
> 
> The main cause of native memory consumption is allocation
> of GrowableArray and VectorSet in next very hot EA method:
> 
> void ConnectionGraph::PointsTo(VectorSet &ptset, Node * n) {
>  VectorSet visited(Thread::current()->resource_area());
>  GrowableArray<uint>  worklist;
> 
> And the cause of a lot calls to os::malloc() is VectorSetI
> iterator which is used only by EA but it is used a lot,
> it could also cause C heap fragmentation:
> 
> SetI_ *VectorSet::iterate(uint &elem) const
> {
>  VSetI_ *foo = (new(ResourceObj::C_HEAP) VSetI_(this));
>  elem = foo->next();
>  return foo;
> }
> 
> The first problem is fixed by reusing structures in PointsTo().
> I also added Reset() method to VectorSet to zero data array
> instead of freeing it.
> 
> The second problem is fixed by adding new simple VectorSetI
> iterator (old iterator is renamed to VectorSetIter) which
> is not based on SetI and doesn't need VSetI_.
> 
> I also fixed compile time statistics for EA since it is now
> part of Optimizer.