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Linux huge page size and ASE page size

Nov 11, 2016 at 07:53 PM

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Hello,

Is there any relation or recommendation regarding to Linux REHL 7 Hugepagesize setting and ASE 16 Sp02 server’s logical page size?

For example:

I have machine with 300Gb RAM and at OS level :

cat /proc/meminfo | grep Hugepagesize

Hugepagesize: 2048 kB

and

ASE page size is 16kb

Should I match ASE logical page size setting "Linux Hugepage size" to 16MB or they are not related at all?

Thank you

Regards

Jose

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4 Answers

Best Answer
Mark A Parsons Nov 11, 2016 at 08:51 PM
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They're not really related (other than, perhaps, making sure they are both powers of 2).

Keep in mind that the default huge page size is 2MB (2048 KB) (so a lot bigger than ASE's pagesize) ... and this is by design as it allow for more efficient memory management at the OS level in linux.

The default huge page size of 2048 KB (2MB) is usually sufficient; then the sysadmin just needs to define the number of huge pages (vm.nr_hugepages).

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Jose Torres Nov 14, 2016 at 12:57 PM
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Mark,

Thank you

Regards

Jose

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Jose Torres Nov 14, 2016 at 01:04 PM
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Mark, One last question:

Regarding this message :

"Warning: Operating System stack size is greater than 2MB. If it is too large, ASE may run out of memory during thread creation. You can reconfigure it using 'limit' (csh) or 'ulimit' (bash)" I found taht it can be ignored.

So if we set ulimit -s to "unlimited " would it help.?

Thank you

Jose

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You haven't mentioned your current stack size so I'm going to assume it's 8192KB (ie, 8MB), which appears to be the default on Linux (at least on the linux systems I have access to).

The warning message is complaining about the stack size being larger than 2MB.

Setting stack size to unlimited won't get rid of the warning message (ie, obviously 'unlimited' > 2MB) so unless you've got some other messages indicating that stack size is too small, I'd refrain from setting stack size to unlimited.

You could check out KBA 2266899 but, oh wait, this is a SAP site/link so you'll need a 'S' id to actually see the KBA ... silly me ... heaven forbid SAP would make this type of info available to the general public.

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Jose Torres Nov 14, 2016 at 05:10 PM
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Thank you Mark

Regards

Jose

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