8201495: [Zero] Reduce limits of max heap size for boot JDK on s390 (original) (raw)
Magnus Ihse Bursie magnus.ihse.bursie at oracle.com
Mon Apr 16 08:58:03 UTC 2018
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On 2018-04-13 15:40, Severin Gehwolf wrote:
Hi,
We (Red Hat) have been building Zero on s390 for a while now. In order to do so we needed to have this patch to reduce the maximum heap size setting for big workloads. Otherwise we see this during (JDK 9) builds: ++ /usr/bin/tee /builddir/build/BUILD/java-9-openjdk-9.0.4.12-5.openjdk9.el7.s390/openjdk/build/jdk/modules/java.base/the.java.basebatch.log ++ /usr/bin/tee /builddir/build/BUILD/java-9-openjdk-9.0.4.12-5.openjdk9.el7.s390/openjdk/build/jdk/modules/java.base/the.java.basebatch.log Error occurred during initialization of VM Could not reserve enough space for 1048576KB object heap NOTE: JDK 9 has the same build logic than JDK 11 in terms of big workloads' JVM switches. Bug: https://bugs.openjdk.java.net/browse/JDK-8201495 webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8201495/webrev.01/
Hi Severin,
As I said in the bug report (didn't notice that you've already sent out a webrev here), I'm not really fond of adding platforms guard if they can be avoided. Normally, Java programs use more or less the same amount of heap regardless of platforms they run on, differing only by platform word size. So if a lower mx is enough on s390 builds, it's mostly likely to be enough on all platforms, and thus the guard is unnecessary, and will only make it harder to update the code in the future.
Also, the value of ms is typically of less concern. While mx is setting an upper bound on resource allocation, ms is more of a "performance hint" to the gc. Unless this is needed for your fix to work, I recommend you leave it at it's current value.
/Magnus
Testing: Run configure on s390 and inspected the big workloads settings: Before: checking flags for bootcycle boot jdk java command for big workloads... -Xms64M -Xmx998M -XX:ThreadStackSize=768 After: checking flags for bootcycle boot jdk java command for big workloads... -Xms256M -Xmx768M -XX:ThreadStackSize=768 This should be fairly low risk, since the check is guarded by s390 archicture checks. Other architectures should be unaffected. Thanks, Severin
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