G1 Performance [Was: JEP 248: Make G1 the Default Garbage Collector]

[Andrew Dinn]

On 29/07/15 19:27, Vitaly Davidovich wrote:
> IIRC Erik's proposal involves TLB shootdowns, which I'm not sure will speed
> this up.  A few months back there was a discussion around this in the
> context of adding full fence with CMS when UseConditionalCardMarking is
> enabled (which I'm not sure if that change went in actually) and
> interaction with precleaning.

A change did go in but not quite as you describe it. As a fix for
JDK-8079315 a /StoreLoad/ barrier was added -- see this changeset:

  http://hg.openjdk.java.net/jdk9/hs-rt/hotspot/rev/a7d15bf7b961

I agree that TLB shootdowns are unlikely to improve performance -- also,
they are a hostage to fortune since you are at the mercy of the OS
implementation as regards both performance and, perhaps to a lesser
degree, correctness.
regards,


Andrew Dinn
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