JEP 522 performance regression with large pages

[Brian S O'Neill]

Yes, I was testing with JDK 24 as the baseline. When testing with JDK 25 
as the baseline, I see the same performance regression. Using 'always' 
instead of 'madvise' does appear to resolve the issue, but this isn't 
that great of a workaround.

I assume it's too late for the fix to be made in time for JDK 25, and so 
a release note is necessary instead? When is JDK 25 u1 due to be released?


On 2025-09-01 02:51 AM, Stefan Johansson wrote:
> Hi Brian,
> 
> As Thomas mentioned you uncovered a problem with THP in JDK 25.
> 
> I guess the reason that you don't see the regression in your baseline is 
> because you compare JEP 522 against JDK 24 (which is not affected by the 
> regression), is that correct?
> 
> The workaround for using THP with G1 in JDK 25 is to configure the THP 
> mode to 'always' instead of 'madvise'.
> 
> Hope this helps,
> Stefan
>