On 5/8/19 5:20 AM, Robbin Ehn wrote:
Correct links:
http://cr.openjdk.java.net/~rehn/8223306/v2/webrev/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/CommandProcessor.java.sdiff.html
http://cr.openjdk.java.net/~rehn/8223306/v2/inc/webrev/
http://cr.openjdk.java.net/~rehn/8223306/v2/webrev/
src/hotspot/share/runtime/thread.hpp
No comments.
src/hotspot/share/runtime/thread.cpp
No comments.
src/hotspot/share/runtime/threadSMR.hpp
No comments.
src/hotspot/share/runtime/vmStructs.cpp
No comments.
It's nice to see that no code is using the old Threads::_thread_list
or JavaThread::next() anymore. I have a vague memory of some Compiler
Thread code still using it back when we first layered in ThreadSMR...
Something about a fast way to find the next CompilerThread...
That must have changed.
Onward...
General comment - Please make sure to update all copyright years before
pushing this changeset.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/CommandProcessor.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/debugger/bsd/BsdDebuggerLocal.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/ObjectHeap.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/DeadlockDetector.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/JavaThread.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/Threads.java
L46:
L47: private static AddressField threadsField;
L48: private static CIntegerField lengthField;
nit - please delete blank line on L46
nit - please reduce the space between type and variable names
(I have no preference if you still keep them aligned)
nit - Please delete blank line on L74.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/tools/PStack.java
old L203: Threads threads = VM.getVM().getThreads();
old L204: for (JavaThread cur = threads.first(); cur != null;
cur = cur.next()) {
new L203: VM.getVM().getThreads().doJavaThreads((cur) -> {
In this case, you did a lambda conversion...
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/tools/StackTrace.java
old L75: for (JavaThread cur = threads.first(); cur !=
null; cur = cur.next(), i++) {
new L75: for (int k = 0; k <
threads.getNumberOfThreads(); k++) {
new L76: JavaThread cur = threads.getJavaThreadAt(k);
In this case, you didn't do a lambda conversion...
I'm trying to grok a reason for the different styles...
Update: Is is maybe a control flow thing? (No, I don't know much
about lambdas.) As in: Loops that "break" or early return are
not amenable to conversion to a lambda... (just guessing)
L74: int i = 1;
Not your bug, but I think that 'i' is not used.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/ui/JavaThreadsPanel.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/AbstractHeapGraphWriter.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/PointerFinder.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/ReversePtrsAnalysis.java
No comments.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/soql/JSJavaVM.java
No comments.
test/hotspot/jtreg/serviceability/sa/ClhsdbField.java
No comments.
test/hotspot/jtreg/serviceability/sa/ClhsdbPrintStatics.java
No comments.
test/hotspot/jtreg/serviceability/sa/ClhsdbVmStructsDump.java
No comments.
This all looks good to me... so thumbs up!
I have some reservations about using lambdas in a debugging tool.
My personal philosophy about debugging tools is that they should
be built on the simplest/most stable technology to reduce the
chances of the more complicated technology failing during a debug
session. I hate it when my debugger crashes!
That said, SA is pretty much standalone so use of lambdas in this
debugging tool shouldn't affect the JVM or core file being debugged.
Again, thumbs up!
Dan
/Robbin
On 2019-05-08 11:17, Robbin Ehn wrote:
Hi David,
I changed to normal for:
http://rehn-ws.se.oracle.com/cr_mirror/8223306/v2/webrev/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/CommandProcessor.java.sdiff.html
Full:
http://rehn-ws.se.oracle.com/cr_mirror/8223306/v2/webrev/
Inc:
http://rehn-ws.se.oracle.com/cr_mirror/8223306/v2/inc/webrev/
Passes t1-2
Thanks, Robbin
On 2019-05-07 09:47, David Holmes wrote:
Hi Robbin,
On 7/05/2019 4:50 pm, Robbin Ehn wrote:
Hi David,
On 5/7/19 12:40 AM, David Holmes wrote:
Hi Robbin,
I have a few concerns here.
First I can't see how you are actually integrating the SA with the
ThreadSMR. You've exposed the _java_thread_list for it to iterate
but IIRC that list can be updated when threads are added/removed
and I'm not seeing how the SA is left iterating a valid list -
we'd normally using a ThreadsListHandle for that ?? (I may need a
refresher on how this list is actually maintained.)
The processes must be paused. If the processes would be running the
linked list is also broken since if we unlink and delete a
JavaThread and then later SA follows that _next pointer.
Ah good point. Thanks for clarifying.
The conversion from external iteration of the list (the for loop)
to internal iteration (passing a lambda to JavaThreadsDo) is also
problematic. First I'd be very wary about introducing lambda
expressions into the SA code - lambda drags in a lot of supporting
code that could have an impact on the way SA functions. There are
places where we have to avoid lambdas due to
bootstrapping/initialization issues and I think the SA may be an
area where we also want to keep the code extremely simple.
There are already several usages of lambdas in SA code, e.g.
LinuxDebuggerLocal.java. SA is not a core module, it's an
application, there is not a bootstrap issue or so.
Hmm okay. Lambda carries a lot of baggage. But if its already being
used ...
Second by using lambda's with internal iteration you've lost the
ability to terminate the iteration loop! In the existing code if
we have a return in the for-loop then we not only terminate the
loop but the enclosing method. With the lambda the "return" just
ends the current iteration and JavaThreadsDo will then continue
with the next thread - so we don't even terminate the iteration
let alone the method performing the iteration. So for places were
we want to process one thread, for example, we will continue to
iterate all remaining threads and just do nothing with them.
That's very inefficient.
That's why I only used the internal iteration where we didn't have
early returns.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/CommandProcessor.java
- original code:
1556 new Command("where", "where { -a | id }", false) {
1557 public void doit(Tokens t) {
...
1564 for (JavaThread thread = threads.first();
thread != null; thread = thread.next()) {
1565 ByteArrayOutputStream bos = new
ByteArrayOutputStream();
1566 thread.printThreadIDOn(new
PrintStream(bos));
1567 if (all || bos.toString().equals(name)) {
1568 out.println("Thread " +
bos.toString() + " Address: " + thread.getAddress());
...
1577 }
1578 if (!all) return;
That looks like an early return to me.
Cheers,
David
-----
Thanks, Robbin
Thanks,
David
On 6/05/2019 5:31 pm, Robbin Ehn wrote:
Hi, please review.
Old threads linked list remove and updated SA to use ThreadsList
array instead.
Issue:
https://bugs.openjdk.java.net/browse/JDK-8223306
Webrev:
http://cr.openjdk.java.net/~rehn/8223306/webrev/
Passes t1-3 (which includes SA tests).
Thanks, Robbin
