[Linux-kernel-mentees] [RFC PATCH 0/2] Add predictive memory reclamation and compaction

Michal Hocko mhocko at kernel.org
Wed Aug 21 14:06:32 UTC 2019

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

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

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