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List:       openjdk-hotspot-gc-dev
Subject:    Re: RFR: 8297487: G1 Remark: no need to keep alive oop constants of nmethods on stack
From:       Richard Reingruber <rrich () openjdk ! org>
Date:       2022-11-30 15:12:23
Message-ID: PTCLoLkXdWL7nhh2A5VbKb3A6yNoA7t8yvcFvvu5u7A=.cba45052-e1af-46a3-8f96-be854dcc7070 () github ! com
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On Wed, 30 Nov 2022 14:40:27 GMT, Albert Mingkun Yang <ayang@openjdk.org> wrote:

> > This pr removes the stackwalks to keep alive oops of nmethods found on stack \
> > during G1 remark as it seems redundant. The oops are already kept alive by the \
> > [nmethod entry barrier](https://github.com/openjdk/jdk/blob/f26bd4e0e8b68de297a9ff93526cd7fac8668320/src/hotspot/share/gc/shared/barrierSetNMethod.cpp#L85)
> >  
> > Additionally it fixes a comment that says nmethod entry barriers are needed to \
> > deal with continuations which, afaik, is not the case. Please correct me and \
> > explain if I'm mistaken. 
> > Testing: the patch is included in our daily CI testing since a week. That is most \
> > JCK and JTREG tests, also in Xcomp mode, Renaissance benchmark and SAP specific \
> > tests with fastdebug and release builds on the standard platforms plus PPC64. \
> > There was no failure I could attribute to this change. 
> > I tried to find a jtreg test that is sensitive to the keep alive by omitting it \
> > in the nmethod entry barrier and also in G1 remark but without success.
> 
> Marked as reviewed by ayang (Reviewer).

Thanks for the review @albertnetymk

-------------

PR: https://git.openjdk.org/jdk/pull/11314


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