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<div class="moz-cite-prefix">Am 18.10.2017 um 10:18 schrieb Erik
Österlund:<br>
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Hi Roman,<br>
<br>
<div class="moz-cite-prefix">On 2017-10-17 23:34, Roman Kennke
wrote:<br>
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<div class="moz-cite-prefix">Am 17.10.2017 um 23:10 schrieb
Roman Kennke:<br>
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<p>The SuspendibleThreadSet API for synchronizing any
non-Java thread with safepoints currently resides under
gc/g1. It is very useful for other GCs too (in particular,
Shenandoah does use it too), so I wanted to move it to a
common location like gc/common. Then Kim Barrett commented
that it might actually be useful for other threads outside
GC land and to put it under runtime/. So I did:</p>
<p><a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Erkennke/8189276/webrev.00/">http://cr.openjdk.java.net/~rkennke/8189276/webrev.00/</a></p>
<p>I also added a generic hook to call the STS from
safepoint sync/desync, which is consequently used by G1
now. In other words, the CollectedHeap API that Erik Ö
introduced is no longer used by G1. Only CMS still uses
that API because it has its own way to sync with
safepoints. I filed <a moz-do-not-send="true"
href="https://bugs.openjdk.java.net/browse/JDK-8189364">another
bug</a> for this. Although I have my doubt it will ever
be fixed. This seems to have been very carefully evolved
(to put it positive), and the risk of breaking it is
relatively high, and thus doesn't seem worth the struggle
to make it fit the STS.<br>
</p>
<p>Issue:<br>
<a moz-do-not-send="true"
href="https://bugs.openjdk.java.net/browse/JDK-8189276">https://bugs.openjdk.java.net/browse/JDK-8189276</a></p>
<p>What do you think? Ok to go in?</p>
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Replying to myself here.<br>
I must admit that I am a bit reluctant to expose it to
runtime/ unless there's a specific need for it. So maybe go
back to the original plan to move it into gc/common and leave
all the rest alone for now? What do others think?<br>
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<br>
Sorry, forgot to add something. One reason why we originally
wanted to move it to gc/common (a new directory) instead of the
existing gc/shared was that Erik H objected that gc/shared would
be built into the minimal VM, and we probably wouldn't want that
unless needed. However, moving it to runtime/ (without actual
need), would achieve just that. So unless we can name an actual
thread that would benefit from synchronizing using the STS, I
suggest to leave the STS code in gc/common for now?<br>
<br>
That would be:<br>
<a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Erkennke/8189276/webrev.01/">http://cr.openjdk.java.net/~rkennke/8189276/webrev.01/</a><br>
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<br>
We had some internal discussions, and the conclusion seems to be
that we would like to not have a new gc/common directory for
build-only purposes, but rather put it in gc/shared and explicitly
mark files we do not want to have compiled in minimal VM in the
make/hotspot/lib/JvmFeatures.gmk build file. You can remove files
from the minimal VM build by explicitly adding files to an exclude
list in that file.<br>
<br>
133: JVM_EXCLUDE_FILES += \<br>
134: concurrentGCThread.cpp \<br>
+++ add your files here<br>
135: plab.cpp<br>
<br>
I tend to agree that avoiding the new gc/common directory is
probably a win right now. Hope you agree with this.<br>
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Sure. This sounds like the best solution so far. Basically back to
my original plan :-)<br>
<br>
<a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Erkennke/8189276/webrev.02/">http://cr.openjdk.java.net/~rkennke/8189276/webrev.02/</a><br>
<br>
Haven't tested minimal build though.<br>
<br>
Roman<br>
<br>
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