RFR(M): 8133749, 8133747, 8133740: NMT detail stack trace cleanup
Chris Plummer
chris.plummer at oracle.com
Tue Aug 2 20:31:28 UTC 2016
Hello,
Please review the following:
webrev:
http://cr.openjdk.java.net/~cjplummer/8133749-8133747-8133740/webrev-01/webrev.hotspot/
Bugs fixed:
JDK-8133749: os::current_frame() is not returning the proper frame on
ARM and solaris-x64
https://bugs.openjdk.java.net/browse/JDK-8133749
JDK-8133747: NMT includes an extra stack frame due to assumption NMT is
making on tail calls being used
https://bugs.openjdk.java.net/browse/JDK-8133747
JDK-8133740: NMT for Linux/x86/x64 and bsd/x64 slowdebug builds includes
NativeCallStack::NativeCallStack() frame in backtrace
https://bugs.openjdk.java.net/browse/JDK-8133740
The above bugs all result in the NMT detail stack traces including extra
frames in the stack traces. Certain frames are suppose to be skipped,
but sometimes are not. The frames that show up are:
NativeCallStack::NativeCallStack
os::get_native_stack
These are both methods used to generate the stack trace, and therefore
should not be included it. However, under some (most) circumstances,
they were.
Also, there was no test to make sure that any NMT detail output is
generated, or that it is correct. I've added one with this webrev. Of
the 27 possible builds (9 platforms * 3 build flavors), only 9 of the 27
initially passed this new test. They were the product and fastdebug
builds for solaris-sparc, bsd-x64, and linux-x64; and the slowdebug
builds for solaris-x64, windows-x86, and windows-x64. All the rest
failed. They now all pass with my fixes in place.
Here's a summary of the changes:
src/os/posix/vm/os_posix.cpp
src/os/windows/vm/os_windows.cpp
JDK-8133747 fixes: There was some frame skipping logic here which was
sort of correct, but was misplace. There are no extra frames being added
in os::get_native_stack() due to lack of inlining or lack of a tail
call, so no need for toSkip++ here. The logic has been moved to
NativeCallStack::NativeCallStack, which is where the tail call is
(sometimes) made, and also corrected (see nativeCallStack.cpp below).
src/share/vm/utilities/nativeCallStack.cpp
JDK-8133747 fixes: The frame skipping logic that was moved here assumed
that NativeCallStack::NativeCallStack would not appear in the call stack
(due to a tail call be using to call os::get_native_stack) except in
slow debug builds. However, some platforms also don't use a tail call
even when optimized. From what I can tell that is the case for 32-bit
platforms and for windows.
src/os_cpu/bsd_x86/vm/os_bsd_x86.cpp
src/os_cpu/windows_x86/vm/os_windows_x86.cpp
src/os_cpu/linux_x86/vm/os_linux_x86.cpp
JDK-8133740 fixes: When _get_previous_fp is not inlined, we need to skip
one extra frame
src/os_cpu/solaris_x86/vm/os_solaris_x86.cpp
JDK-8133749 fixes: os:current_frame() was not consistent with other
platforms and needs to skip one more frame. This means it returns the
frame for the caller's caller. So when called by os:get_native_stack(),
it returns the frame for whoever called os::get_native_stack(). Although
not intuitive, this is what os:get_native_stack() expects. Probably a
method rename and/or a behavior change is justified here, but I would
prefer to do that with a followup CR if anyone has a good suggestion on
what to do.
test/runtime/NMT/CheckForProperDetailStackTrace.java
This is the new NTM detail test. It checks for frames that shouldn't be
present and validates at least one stack trace is what is expected.
I verified that the above test now passes on all supported platforms,
and also did a full jprt "-testset hotpot" run. I plan on doing some RBT
testing with NMT detail enabled before committing.
Regarding the community contributed ports that Oracle does not support,
I didn't make any changes there, but it looks like some of these bugs do
exist. Notably:
-linux-aarch64: Looks like it suffers from JDK-8133740. The changes done
to the
os_linux_x86.cp should also be applied here.
-linux-ppc: Hard to say for sure since the implementation of
os::current_frame is
different than others, but it looks to me like it suffers from both
JDK-8133749
and JDK-8133740.
-aix-ppc: Looks to be the same implementation as linux-ppc, so would
need the
same changes.
These ports may also be suffering from JDK-8133747, but that fix is in
shared code (nativeCallStack.cpp). My changes there will need some
tweaking for these ports they don't use a tail call to call
os::get_native_stack().
If the maintainers of these ports could send me some NMT detail output,
I can advise better on what changes are needed. Then you can implement
and test them, and then send them back to me and I'll include them with
my changes. What I need is the following command run on product and
slowdebug builds. Initially run without any of my changes applied. If
needed I may followup with a request that they be run with the changes
applied:
bin/java -XX:+UnlockDiagnosticVMOptions -XX:NativeMemoryTracking=detail
-XX:+PrintNMTStatistics -version
thanks,
Chris
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