RFR (XXS): 8136680: Enable adaptive IHOP by default

Jon Masamitsu jon.masamitsu at oracle.com
Tue Nov 24 18:33:32 UTC 2015

Thomas, Looks good.

36 product(bool, G1UseAdaptiveIHOP, true, \
   37           "Adaptively adjust InitiatingHeapOccupancyPercent from the "      \
38 "initial value. The policy tries to start marking as late as " \
39 "possible.")

Let me suggest an alternate comment though.

"Dynamically adjust the initiating heap occupancy from the  initial 
value of
InitiatingHeapOccupancyPercent.  The policy attempts to start marking in
time based on application behavior."

Do we need G1 in the name of the flag?  Would UseAdaptiveIHOP be
sufficient?   Or maybe UseDynamicIHOP?  Or  (I write this with some
trepidation) would the flag be better named 
or UseDynamicInitiatingHeapOccupancy?

I'm asking the question now because I don't want to ask it the next time
we do a cleanup of flag names.  I can live with any of the above.


On 11/24/2015 02:14 AM, Thomas Schatzl wrote:
> Hi all,
>    can I have reviews for the following small change that enables
> adaptive IHOP by default by setting G1UseAdaptiveIHOP to true by
> default.
> This feature improves usability of G1 as the user does not need to care
> about the InitiatingHeapOccupancyPercent option any more. It will be set
> automatically based on predictions of previous application behavior.
> The existing InitiatingHeapOccupancyPercent option still serves as
> initial value for the predictions.
> Of course, by manually setting G1UseAdaptiveIHOP to false, original
> behavior is preserved.
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8136680
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8136680/webrev/
> Testing:
> Previous dependent CRs adding adaptive IHOP functionality. Local build
> for this particular change.
> Thanks,
>    Thomas

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