Huge pages on PPC64

[Lindenmaier, Goetz]

Hi Gustavo, 

At some point this was working, but we don't test this as 
you always have to configure a machine to support large pages.
The default configuration of our machines does not support it, see also 
more /proc/meminfo | grep HugePages.
So it might well be that it's no more working. 

Anyways, there is now transparent huge pages which works differently.
Further, usually we run with 64k pages on ppc so that the page overhead is not
as high as on x86 where you often have 4k pages.

So feel free to improve the situation.

Best regards,
  Goetz.

> -----Original Message-----
> From: ppc-aix-port-dev [mailto:ppc-aix-port-dev-
> bounces at openjdk.java.net] On Behalf Of Gustavo Romero
> Sent: Montag, 24. Oktober 2016 18:50
> To: ppc-aix-port-dev at openjdk.java.net
> Subject: Huge pages on PPC64
> Importance: High
> 
> Hi,
> 
> Is Huge Pages properly supported by OpenJDK on PPC64 and PPC64 LE?
> 
> I did a simple test like:
> 
> # uname -a
> Linux tm 4.4.0-38-generic #57-Ubuntu SMP Tue Sep 6 15:42:33 UTC 2016
> x86_64 x86_64 x86_64 GNU/Linux
> # fgrep Huge /proc/meminfo
> AnonHugePages:     12288 kB
> HugePages_Total:     256
> HugePages_Free:      256
> HugePages_Rsvd:        0
> HugePages_Surp:        0
> Hugepagesize:       2048 kB
> # java -XX:+PrintCommandLineFlags -XX:+UseLargePages -Xms256m -
> Xmx256m StrictMath_cos
> -XX:InitialHeapSize=268435456 -XX:MaxHeapSize=268435456 -
> XX:+PrintCommandLineFlags -XX:+UseCompressedClassPointers -
> XX:+UseCompressedOops -XX:+UseLargePages -XX:+UseParallelGC
> 0.1709843554185943
> # java -version
> openjdk version "1.8.0_91"
> OpenJDK Runtime Environment (build 1.8.0_91-8u91-b14-3ubuntu1~16.04.1-
> b14)
> OpenJDK 64-Bit Server VM (build 25.91-b14, mixed mode)
> 
> 
> on x64 all went well, but on PPC64 I'm getting an error as if the amount
> of space requested was greater than HugePages_Total * Hugepagesize,
> which
> is no true:
> 
> # uname -a
> Linux pub 4.5.0-rc4-powerpc64le #1 SMP Debian 4.5~rc4-1~exp1 (2016-02-18)
> ppc64le GNU/Linux
> # fgrep Huge /proc/meminfo
> AnonHugePages:   7831552 kB
> HugePages_Total:    1024
> HugePages_Free:     1024
> HugePages_Rsvd:        0
> HugePages_Surp:        0
> Hugepagesize:      16384 kB
> # java -XX:+PrintCommandLineFlags -Xms256m -Xmx256m -
> XX:+UseLargePages StrictMath_cos
> -XX:InitialHeapSize=268435456 -XX:MaxHeapSize=268435456 -
> XX:+PrintCommandLineFlags -XX:+UseCompressedClassPointers -
> XX:+UseCompressedOops -XX:+UseLargePages -XX:+UseParallelGC
> OpenJDK 64-Bit Server VM warning: Failed to reserve large pages memory
> req_addr: 0x00000000f0000000 bytes: 268435456 (errno = 16).
> OpenJDK 64-Bit Server VM warning: Failed to reserve large pages memory
> req_addr: 0x00000007b0000000 bytes: 268435456 (errno = 16).
> OpenJDK 64-Bit Server VM warning: Failed to reserve large pages memory
> req_addr: 0x0000000000000000 bytes: 301989888 (errno = 16).
> # java -version
> openjdk version "1.8.0_102"
> OpenJDK Runtime Environment (build 1.8.0_102-8u102-b14.1-2-b14)
> OpenJDK 64-Bit Server VM (build 25.102-b14, mixed mode)
> 
> 
> Am I missing something here or something is planned (tho I could not find a
> JEP or JBS on it...)?
> 
> Thank you.
> 
> 
> Regards,
> Gustavo