[aarch64-port-dev ] jdk11 fastdebug seems to have slowed down.

Vladimir Kozlov vladimir.kozlov at oracle.com
Wed Aug 1 17:30:34 UTC 2018

Which test shows slowdown? Whould be nice to find when (which jdk11 
build) it started?

Is it possible that find_pc_desc_internal() is called more then before?

Is it linear_search() takes long? It is called only in debug VM. Or 
loops in find_pc_desc_internal()?:


I don't see any big changes in this code in jdk 11. Coleen removed 
ValueObj (8173070) but it was "" empty for gcc for long time.


On 8/1/18 9:23 AM, Andrew Dinn wrote:
> Hi Dave,
> On 01/08/18 16:53, Dave Nuechterlein wrote:
>> I have traced the difference down to
>> src/hotspot/share/code/compiledMethod.hpp.  The
>> PcDescContainer::find_pc_desc_internal seems to be doing a lot of
>> searching of long lists.
>> This obviously might not be a Aarch64 port issue, but rather a
>> hotspot issue.  If anyone here has any experience with the whole
>> PcDescContainer, or has seen fastdebug execution times escalating, I
>> would appreciate getting any kind of help.  The PcDescContainer
>> appears to be some way for a method to understand its calling
>> hierarchy.
> Yes, a PcDesc is used to translate a JITted code location to a bytecode
> location and, from there, potentially to a source code line. It is
> needed in order to generate correct stack traces.
> PcDesc entries can also be used to associate line numbers with arbitrary
> JITted code but there is no guarantee that there will be a useful PcDesc
> that you can reliably associate with any given JITted PC. Safepoints,
> call locations, exception throw points and traps should be mapped. Other
> locations may not have an associated PcDesc and searching (forwards or
> backwards) for the nearest one to a given pc address may or may not land
> you at a related source line.
> If you are seeing a slow down because of long searches of PcDesc lists
> then this suggests that at some point someone has added more PcDesc
> entries. I don't recall seeing any change go in that might have led to
> this but perhaps the hotspot-compiler or runtime devs (in CC) might know
> of one. What was the jdk release you are comparing against where this
> slowdown did not show?
> regards,
> Andrew Dinn
> -----------
> Senior Principal Software Engineer
> Red Hat UK Ltd
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> Directors: Michael Cunningham, Michael ("Mike") O'Neill, Eric Shander

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