Transparent huge pages patch

[Daniel Micay]

On 12/02/15 05:08 AM, Tommy Reilly wrote:
> We (nuodb) developed a patch to have jemalloc call MADV_NOHUGEPAGE on
> all memory it mapped but this only works if THP setting on OS is
> [madvise] so its not a complete fix. It does give our customers the
> flexibility to use madvise instead of never to work around this problem.
>   If such a patch would be welcome I will put one together but we
> consider it a half fix.   Personally I think linux should be changed so
> that THP can be disabled by a process regardless of system setting but
> that doesn't appear to be possible at the moment.

If it's on 'madvise', then it will only use huge pages if ranges are
marked with MADV_HUGEPAGE. The MADV_NOHUGEPAGE hint is a no-op unless
the range was already marked with MADV_HUGEPAGE or if it's set to the
'always' setting. It can certainly be disabled by a process regardless
of the system setting, but it's only opt-out with 'always' anyway.

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