RFR(xs): 8202772: NMT erroneously assumes thread stack boundaries to be page aligned

Thomas Stüfe thomas.stuefe at gmail.com
Tue Jun 12 07:23:18 UTC 2018


Thanks, Goetz!

On Tue, Jun 12, 2018 at 9:03 AM, Lindenmaier, Goetz
<goetz.lindenmaier at sap.com> wrote:
> Hi Thomas,
>
> looks good.
>
> Best regards,
>   Goetz.
>
>> -----Original Message-----
>> From: hotspot-runtime-dev [mailto:hotspot-runtime-dev-
>> bounces at openjdk.java.net] On Behalf Of Thomas Stüfe
>> Sent: Dienstag, 12. Juni 2018 06:59
>> To: Hotspot dev runtime <hotspot-runtime-dev at openjdk.java.net>
>> Subject: RFR(xs): 8202772: NMT erroneously assumes thread stack
>> boundaries to be page aligned
>>
>> Dear all,
>>
>> may I please have reviews for this fix, which - for now - disables
>> thread stack tracking for NMT on AIX.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8202772
>> Webrev: http://cr.openjdk.java.net/~stuefe/webrevs/8202772-NMT-
>> erroneously-assumes-thread-stack-boundaries-to-be-page-
>> aligned/webrev.00/webrev/
>>
>> On AIX, we have two problems:
>>
>> - NMT assumes stack boundaries to be page aligned. This is wrong but
>> on all platforms other than AIX does not matter.
>> - the way mincore() is used to read residency of pages needs to be
>> adapted since on AIX, os::vm_page_size() is not necessarily the page
>> size used by mincore() - which is quite dangerous.
>>
>> Since JDK-8204552 was added to deal with the first point, it makes
>> sense to wait until that issue is finished. Until then, I'd like to
>> disable thread stack recognition in NMT for AIX. We can revisit this
>> topic again once we can spare time for it and JDK-8204552 has been
>> done.


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