RFR(M): JDK-8203321: Windows: assert(current_query_index < process_query_set->size) failed: invariant

[Markus Gronlund]

Thank you Robbin.

Markus

-----Original Message-----
From: Robbin Ehn 
Sent: den 30 maj 2018 22:26
To: Markus Gronlund <markus.gronlund at oracle.com>; hotspot-runtime-dev at openjdk.java.net
Subject: Re: RFR(M): JDK-8203321: Windows: assert(current_query_index < process_query_set->size) failed: invariant

Hi Markus,

I'm not familiar with PDH, but given your description and the code looks good.

Thanks, Robbin

On 2018-05-22 21:24, Markus Gronlund wrote:
> Greetings,
> 
> Kindly asking for reviews for the following change:
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8203321
> Webrev: http://cr.openjdk.java.net/~mgronlun/8203321/webrev00/
> 
> Summary:
> 
> For some context about what this is about, please see this (now) relatively old issue: https://bugs.openjdk.java.net/browse/JDK-8019921
> 
> The porting work that brought this code from closed to open were optimistic in that the following PDH query,  "\Process(java#n)\ID Process", performed relatively stable on Windows 10.
> An invariant was added in that your ID Process query would never return an index that was lower than the index at construction.
> 
> During testing, it was discovered that this invariant did not hold, especially when running on Windows Server 2012 R2 and there is a high churn rate with many processes with the same base name ("java#") starting and stopping (stressing PDH list of processes).
> 
> We have to reinsert back the original code that handled the case where the PDH process list is not stable (that were originally put in place with JDK-8019921).
> The defensive logic is located at lines 418 - 422.
> 
> I had to rework some related code to make some room for this as well as to keep track of the previous process index.
> 
> Thanks
> Markus
>