Making PrintEscapeAnalysis a diagnostic option on product VM? (original) (raw)

Chris Newland cnewland at chrisnewland.com
Thu Jul 9 20:10:40 UTC 2015

Hi,

I've found a way to output EA information via LogCompilation from the product VM including BCIs so that I can annotate bytecode but it relies on the following block from opto/compile.cpp being entered:

void Compile::Init(int aliaslevel) { ...

if (debug_info()->recording_non_safepoints()) { set_node_note_array(new(comp_arena()) GrowableArray<Node_Notes*> (comp_arena(), 8, 0, NULL)); set_default_node_notes(Node_Notes::make(this)); }

Without this, the Note_Notes are not present in the ideal nodes and I can't fully identify what was eliminated.

It looks like this will only execute when DebugNonSafepoints is true and this is a diagnostic VM option.

Does anyone have an alternative method for getting BCIs for eliminated allocs without using Note_Notes?

Thanks,

Chris

On Fri, June 19, 2015 16:09, Vladimir Kozlov wrote:

Agree.

Vladimir K On 6/19/15 5:10 AM, Vladimir Ivanov wrote:

What do you think the next step is?

I'm not a committer but I'd be happy to submit a patch/webrev that outputs LogCompilation XML for the kind of EA info I think would be useful. Go for it. If you are a Contributor (signed OCA), we'll review and accept your patch with gratitude. Keep in mind, that when you touch LogCompilation output format, you should update logc tool (src/share/tools/LogCompilation/ [1]) as well. I've just seen Vitaly's post and I agree a tty 1-liner for each elimination would also be nice. Feel free to enhance -XX:+PrintEscapeAnalysis output as well, if you find it useful. Best regards, Vladimir Ivanov [1] http://hg.openjdk.java.net/jdk9/jdk9/hotspot/file/tip/src/share/tools/L ogCompilation Thanks, Chris On Fri, June 19, 2015 12:03, Vladimir Ivanov wrote: Chris,

I'd suggest to look into enhancing LogCompilation output instead of parsing VM output. It doesn't require any flag changes and fits nicely into existing LogCompilation functionality, so we can integrate it into the product, relieving you and JITWatch users from building a companion VM. Best regards, Vladimir Ivanov On 6/19/15 1:16 PM, Chris Newland wrote: Hi, hope this is the correct list (perhaps serviceability?)

I'm experimenting with some HotSpot changes that log escape analysis decisions so that I can visualise eliminated allocations at the source and bytecode levels in JITWatch[1]. My plan was to build a companion VM for JITWatch based on the product VM that would allow users to inspect some of the deeper workings such as EA and DCE that are not present in the LogCompilation output. I mentioned this to some performance guys at Devoxx and they didn't like the custom VM idea and suggested I put in a request to consider making -XX:+PrintEscapeAnalysis available under -XX:+UnlockDiagnosticVMOptions on the product VM (it's currently a notproduct option). If this is something you would consider than could I also request consideration of -XX:+PrintEliminateAllocations. All I would need is the class, method, and bci of each NoEscape detected. Kind regards, Chris [1] https://github.com/AdoptOpenJDK/jitwatch

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