Memory Compaction Question

Memory Compaction Question

[Daniel Hoffman]

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In the Linux Kconfig documentation for memory compaction, you mention
that almost nobody should turn the option off, and if so that you'd
like to hear about why at this email address.

Has anybody email'd you to explain why they'd need it turned off? I'm
doing R&D in this area and understanding these edge cases (if they
exist) would be great.

Thanks!

-- 
Daniel Hoffman
University of Illinois Urbana-Champaign
Mobile: (618)-980-5804

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Re: Memory Compaction Question

[Vlastimil Babka]

On 10/12/21 20:35, Daniel Hoffman wrote:
> In the Linux Kconfig documentation for memory compaction, you mention
> that almost nobody should turn the option off, and if so that you'd
> like to hear about why at this email address.
> 
> Has anybody email'd you to explain why they'd need it turned off? I'm

I don't personally recall about a mail triggered specifically by this
kconfig hint. There have been cases where people complained about high
overhead (e.g. CPU usage) which was sometimes due to bugs. A common non-bug
reason for high usage has been transparent hugepages (THP). The default
settings for THPs today should mean that compaction will not be tried as
hard in that context, but many people also learned from various old blogs
that they should be disabling THP altogether and keep doing it.

> doing R&D in this area and understanding these edge cases (if they
> exist) would be great.
> 
> Thanks!
> 
> 
> Screenshot from 2021-10-12 13-35-03.png
>