[8u] RFR 8250928: JFR: Improve hash algorithm for stack traces

[Jaroslav Bachorík]

Now, when https://bugs.openjdk.java.net/browse/JDK-8252754 has been
fixed I think we can move on with this backport.

Any objections?

Cheers,

-JB-

On Tue, Sep 1, 2020 at 12:01 PM Aleksey Shipilev <shade at redhat.com> wrote:
>
> On 9/1/20 11:56 AM, Aleksey Shipilev wrote:
> > On 8/31/20 7:11 PM, Jaroslav Bachorík wrote:
> >> Please, review this backport of a hash-collision reducing fix in JFR
> >> stacktrace values from the main line.
> >>
> >> JIRA: https://bugs.openjdk.java.net/browse/JDK-8250928
> >> Webrev: http://cr.openjdk.java.net/~jbachorik/8250928/8u/webrev/
> >
> > 8u backport looks fine.
>
> Oh wait, hold on a sec.
>
> The original changeset [1] only changes the bit in JfrStackTrace::record_safe. Why does this
> backport change JfrStackTrace::record_safe and JfrStackTrace::record_thread?
>
> --
> Thanks,
> -Aleksey
>
> [1]
> https://hg.openjdk.java.net/jdk/jdk/file/c3cc9ac0ede2/src/hotspot/share/jfr/recorder/stacktrace/jfrStackTrace.cpp
>