RFR(M): 8133749, 8133747, 8133740: NMT detail stack trace cleanup

Chris Plummer chris.plummer at oracle.com
Thu Aug 4 21:53:27 UTC 2016


On 8/2/16 1:31 PM, Chris Plummer wrote:
> 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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