Re: Are there still some methods that could be used by the Linux kernel to reduce memory fragmentation while both CONFIG-MIGRATION and CONFIG-COMPACTION are disabled?

["孙世龙 sunshilong" <sunshilong369@gmail.com>]

Thank you for your attention to this matter.

>> Are there still some methods that could be used by the Linux kernel
>> to reduce memory fragmentation while both CONFIG-MIGRATION
>> and CONFIG-COMPACTION are disabled?
>
>
>We do have mobility grouping on pageblock order.
>Also, I think you can use ZONE_MOVABLE without migration and compaction,
>to at least locally limit unmovable fragmentation.
It's a good news.

Could you please explain that in more detail for me or suggest some documents
for me to go through.

As per the post(http://lkml.iu.edu/hypermail/linux/kernel/1703.1/06782.html),
I think it's something like ZONE_NORMAL. And I find that
"ZONE_MOVEABLE" is available on Linux-v4.9.

>>
>> Are there some system settings that could make for this goal?
>
>Why don't you want page compaction/migration?

Because I am using a real-time system(and I have to apply a patch
to Linux kernel), I have no choice other than disabling these
aforementioned options.

Is there some potential problems that I should be aware of if I enable
"ZONE_MOVABLE" on real-time system?

Best Regards.

David Hildenbrand <david@redhat.com> 于2020年6月24日周三 下午5:53写道：
>
> On 23.06.20 17:52, 孙世龙 sunshilong wrote:
> > Are there still some methods that could be used by the Linux kernel
> > to reduce memory fragmentation while both CONFIG-MIGRATION
> > and CONFIG-COMPACTION are disabled?
>
> We do have mobility grouping on pageblock order.
>
> Also, I think you can use ZONE_MOVABLE without migration and compaction,
> to at least locally limit unmovable fragmentation.
>
> >
> > Are there some system settings that could make for this goal?
>
> Why don't you want page compaction/migration?
>
> --
> Thanks,
>
> David / dhildenb
>