RFR(xxs): 8187230: [aix] Leave OS guard page size at default for non-java threads instead of explicitly setting it

[Lindenmaier, Goetz]

Thanks, looks good now!

Best regards,
  Goetz.

> -----Original Message-----
> From: Thomas Stüfe [mailto:thomas.stuefe at gmail.com]
> Sent: Donnerstag, 7. September 2017 15:47
> To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>
> Cc: ppc-aix-port-dev at openjdk.java.net; HotSpot Open Source Developers
> <hotspot-dev at openjdk.java.net>
> Subject: Re: RFR(xxs): 8187230: [aix] Leave OS guard page size at default for
> non-java threads instead of explicitly setting it
> 
> Hi Goetz,
> 
> thanks for the review!
> 
> Corrected webrev: http://cr.openjdk.java.net/~stuefe/webrevs/8187230-
> aix-leave-os-guard-page-size-at-default-for-non-java-
> threads/webrev.01/webrev/
> 
> Thanks, Thomas
> 
> 
> On Thu, Sep 7, 2017 at 2:20 PM, Lindenmaier, Goetz
> <goetz.lindenmaier at sap.com <mailto:goetz.lindenmaier at sap.com> >
> wrote:
> 
> 
> 	Hi Thomas,
> 
> 	looks good except for that you missed setting the guard pages size to
> zero
> 	for compiler threads. Compiler threads are Java Threads and thus get
> 	our guard pages.
> 
> 	Best regards,
> 	  Goetz.
> 
> 
> 	> -----Original Message-----
> 	> From: hotspot-dev [mailto:hotspot-dev-
> bounces at openjdk.java.net <mailto:hotspot-dev-
> bounces at openjdk.java.net> ] On
> 	> Behalf Of Thomas Stüfe
> 	> Sent: Donnerstag, 7. September 2017 12:02
> 	> To: ppc-aix-port-dev at openjdk.java.net <mailto:ppc-aix-port-
> dev at openjdk.java.net>
> 	> Cc: HotSpot Open Source Developers <hotspot-
> dev at openjdk.java.net <mailto:hotspot-dev at openjdk.java.net> >
> 	> Subject: RFR(xxs): 8187230: [aix] Leave OS guard page size at
> default for non-
> 	> java threads instead of explicitly setting it
> 	>
> 	> Hi all,
> 	>
> 	> may I please have a review for this small change:
> 	>
> 	> Bug:
> 	> https://bugs.openjdk.java.net/browse/JDK-8187230
> <https://bugs.openjdk.java.net/browse/JDK-8187230>
> 	>
> 	> Webrev:
> 	> http://cr.openjdk.java.net/~stuefe/webrevs/8187230-aix-
> <http://cr.openjdk.java.net/~stuefe/webrevs/8187230-aix->
> 	> leave-os-guard-page-size-at-default-for-non-java-
> 	> threads/webrev.00/webrev/
> 	>
> 	> The change is very subtle.
> 	>
> 	> Before, we would set the OS guard page size for every thread - for
> java
> 	> threads disable them, for non-java threads we'd set them to 4K.
> 	>
> 	> Now, we still disable them for java threads but leave them at the
> OS
> 	> default size for non-java threads.
> 	>
> 	> The really important part is the disabling of OS guard pages for java
> 	> threads, where we have a VM guard pages in place and do not
> want to spend
> 	> more memory on OS guards. We do not really care for the exact
> size of the
> 	> OS guard pages for non-java threads, and therefore should not set
> it - we
> 	> should leave the size in place the OS deems sufficient. That also
> spares us
> 	> the complexity of handling the thread stack page size, which on AIX
> may be
> 	> different from os::vm_page_size().
> 	>
> 	> Thank you and Kind Regards, Thomas
> 
>