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

Andrew Dinn adinn at redhat.com
Thu Aug 2 08:02:32 UTC 2018

On 01/08/18 18:14, Andrew Haley wrote:
> On 08/01/2018 05:23 PM, Andrew Dinn wrote:
>> 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?
> There's no need to speculate.  Just run the fastdebug build in a debugger and
> see who's calling find_pc_desc_internal().  It shouldn't take any more than half
> an hour to find out.
Well, running up a debugger is almost always a good idea.

However, I know (having done what you suggest in the past) that PcDesc
searches have always been executed as part of the assert/verify code
that executes in fastdebug mode (but not in product mode). The problem
may possibly be caused by new calls but, given the description of what
Dave observed in the latest build (and, by implication, did nto see in
previous builds), it sounds like the problem is more PcDesc data.

Tracking the calls might help pin down the former problem but I doubt it
will explain much in the latter case. If it is that second case then
tracking the calls which create the data would be a good idea. At the
least it would pin down places to look for recent changes.


Andrew Dinn
Senior Principal Software Engineer
Red Hat UK Ltd
Registered in England and Wales under Company Registration No. 03798903
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