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SubjectRe: [RFC PATCH 0/2] Add predictive memory reclamation and compaction
On Thu 15-08-19 14:51:04, Khalid Aziz wrote:
> Hi Michal,
>
> The smarts for tuning these knobs can be implemented in userspace and
> more knobs added to allow for what is missing today, but we get back to
> the same issue as before. That does nothing to make kernel self-tuning
> and adds possibly even more knobs to userspace. Something so fundamental
> to kernel memory management as making free pages available when they are
> needed really should be taken care of in the kernel itself. Moving it to
> userspace just means the kernel is hobbled unless one installs and tunes
> a userspace package correctly.

From my past experience the existing autotunig works mostly ok for a
vast variety of workloads. A more clever tuning is possible and people
are doing that already. Especially for cases when the machine is heavily
overcommited. There are different ways to achieve that. Your new
in-kernel auto tuning would have to be tested on a large variety of
workloads to be proven and riskless. So I am quite skeptical to be
honest.

Therefore I would really focus on discussing whether we have sufficient
APIs to tune the kernel to do the right thing when needed. That requires
to identify gaps in that area.
--
Michal Hocko
SUSE Labs

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