Hi Paul,
The CSR proposes this method in java.lang.management.ThreadMXBean as a
Java SE feature.
Has this been discussed with the GC team to commit measuring current
thread's allocated bytes as Java SE feature? Can this be supported by
all JVM implementation? What is the overhead if this is enabled by
default? Does it need to be disabled? This metric is from TLAB that
might be okay. This needs advice/discussion with GC experts.
I see that CSR mentions it can be disabled and link to
isThreadAllocatedMemoryEnabled() and setThreadAllocatedMemoryEnabled()
methods but these methods are defined in com.sun.management.ThreadMXBean.
As Alan points out, current thread makes sense only in local VM
management. When this is monitored from a JMX client (e.g. jconsole to
connect to a running JVM, "currentThreadAllowcatedBytes" attribute is
the current thread in jconsole process which invoking Thread::currentThread?
Mandy
On 8/28/19 12:22 PM, Hohensee, Paul wrote:
Please review a performance improvement for
ThreadMXBean.getThreadAllocatedBytes and the addition of
getCurrentThreadAllocatedBytes.
JBS issue:https://bugs.openjdk.java.net/browse/JDK-8207266
Webrev:http://cr.openjdk.java.net/~phh/8207266/webrev.00/
CSR:https://bugs.openjdk.java.net/browse/JDK-8230311
Previous email threads:
https://mail.openjdk.java.net/pipermail/serviceability-dev/2018-July/024441.html
https://mail.openjdk.java.net/pipermail/serviceability-dev/2018-August/024763.html
The CSR is for adding ThreadMXBean.getCurrentThreadAllocatedBytes. I’d
be great for someone to review it.
I took Mandy’s advice and put the fast paths in the library code. I
added a new JMM method GetOneThreadsAllocatedBytes that works the same
as GetThreadCpuTime: it uses a thread_id value of zero to distinguish
the current thread. On my Mac laptop, the result runs 47x faster for
the current thread than the old implementation.
The 3 tests intest/jdk/com/sun/management/ThreadMXBean all pass. I
added code to ThreadAllocatedMemory.java to test
getCurrentThreadAllocatedBytes as well as variations on
getThreadAllocatedBytes(id). A submit repo job is in progress.
Thanks,
Paul
