[9] RFR(S): 8034839: jvm hangs with gc/gctests/LoadUnloadGC test

Vladimir Kozlov vladimir.kozlov at oracle.com
Fri Feb 21 11:27:49 PST 2014

Lets discuss it on hotspot-dev.

Note the current hashtable allocates only in c_heap. Albert added 
hashtable which can allocate in thread local resource area for temporary 
table and c_heap for long live table.


So you restored code in dependencies.?pp to one before 7194669 fix. Right?

I think you need to follow GrowableArray example to name parameter "bool 
C_heap = false" instead of "bool resource_mark". It should be saved in a 
field because you need to free c_heap in destructor if C-heap is used:

~GrowableArray()  { if (on_C_heap()) clear_and_deallocate(); }

Also I think you should avoid call to contains(item) in add() to avoid 
doing the same thing twice.

You should implement remove().


On 2/21/14 12:04 AM, Albert wrote:
> Hi,
> could I get reviews for this small patch?
> Bug: https://bugs.openjdk.java.net/browse/JDK-8034839
> Problem: The problem is that the patch (7194669) - which was supposed to
> speed-up dependency checking
>                 causes a performance regression. The reason for the
> performance regression is that most dependencies
>                 are unique, so we have the overhead of determining if
> the dependency is already checked plus the
>                 overhead of dependency checking. The overhead of
> searching is significant, since we perform
>                 a linear search on 6000+ items each time.
> Solution: Use a hashtable instead of linear search to lookup already
> checked dependencies. The new hashtable
>                 is very rudimentary. It provides only the required
> functionality to solve this bug. However, the functionality
>                 can be easily extended as needed.
> Testing: jprt, failing test case, nashorn. The failing test case
> completes in approx. the same time as before 7194669.
>               For nashorn + Octane, this patch yields the following
> times spent for dependency checking:
>                with this patch:  844s
>                         7194669: 1080s
>             before 7194669: 5223s
> webrev: http://cr.openjdk.java.net/~anoll/8034939/webrev.00/
> Thanks,
> Albert

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