Mailinglist Archive: opensuse (389 mails)

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Re: [opensuse] Transparent Huge Pages
  • From: Per Jessen <per@xxxxxxxxxxxx>
  • Date: Tue, 19 Mar 2019 14:27:13 +0100
  • Message-id: <q6qqnh$mdm$2@saturn.local.net>
Dave Howorth wrote:

On Tue, 19 Mar 2019 13:49:46 +0100
Per Jessen <per@xxxxxxxxxxxx> wrote:

The settings are fairly obvious -

always - always use huge pages
never - never use huge pages
madvise - use huge pages when madvise() requests it.

I am also not certain of when the latter will be useful.

I don't understand why madvise isn't the most useful. Surely it is
reasonable that applications that want huge pages simply ask for them?

Just to be on the safe side - madvise() is for apps to tell the kernel
about their intended use of memory, i.e. size and access pattern. I
guess it means using 2M pages if the app consumes memory in large
chunks.

Wrt redis, I guess it uses lots of small chunks of memory, which
could suffer from always using chunks that are much bigger than
needed.

Indeed, but I still don't understand why it insists on 'never'. Surely
'madvise' fixes its problem?

Erroring on the side of caution ? if they understand madvise() as
little as us, saying 'never' is safe.



--
Per Jessen, Zürich (7.4°C)
http://www.hostsuisse.com/ - dedicated server rental in Switzerland.


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