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

[Chris Plummer]

Hi Thomas,

Is there a reason this shouldn't also be done for linux?

thanks,

Chris

On 9/7/17 3:02 AM, Thomas Stüfe wrote:
> Hi all,
>
> may I please have a review for this small change:
>
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8187230
>
> Webrev:
> 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