RFR(M): 8205921: Optimizing best-of-2 work stealing queue selection

[Kim Barrett]

> On Jul 25, 2018, at 11:09 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi all,
> 
>  could I have reviews for this change to work stealing that
> significantly decreases the amount of unsuccessful steal attempts
> initially worked on by Zhengyu from RedHat [0]?
> 
> […]

> CR:
> https://bugs.openjdk.java.net/browse/JDK-8205921
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8205921/webrev/
> Testing:
> hs-tier1-4
> 

Looks good.

One minor issue, for which I don't need a new webrev.

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src/hotspot/share/gc/shared/taskqueue.inline.hpp
 235   assert(sizeof(int) == 4, "I think this relies on that");

Use STATIC_ASSERT instead of assert.

Although I think the actual requirement is INT_MAX >= m.

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