Re: [PATCH v6 mm-new 00/10] mm, bpf: BPF based THP order selection

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Tue, Aug 26, 2025 at 09:42:30AM +0200, David Hildenbrand wrote:
> On 26.08.25 09:19, Yafang Shao wrote:
> > Background
> > ==========
> >
> > Our production servers consistently configure THP to "never" due to
> > historical incidents caused by its behavior. Key issues include:
> > - Increased Memory Consumption
> >    THP significantly raises overall memory usage, reducing available memory
> >    for workloads.
> >
> > - Latency Spikes
> >    Random latency spikes occur due to frequent memory compaction triggered
> >    by THP.
> >
> > - Lack of Fine-Grained Control
> >    THP tuning is globally configured, making it unsuitable for containerized
> >    environments. When multiple workloads share a host, enabling THP without
> >    per-workload control leads to unpredictable behavior.
> >
> > Due to these issues, administrators avoid switching to madvise or always
> > modes—unless per-workload THP control is implemented.
> >
> > To address this, we propose BPF-based THP policy for flexible adjustment.
> > Additionally, as David mentioned [0], this mechanism can also serve as a
> > policy prototyping tool (test policies via BPF before upstreaming them).
>
> There is a lot going on and most reviewers (including me) are fairly busy
> right now, so getting more detailed review could take a while.
>
> This topic sounds like a good candidate for the bi-weekly MM alignment
> session.
>
> Would you be interested in presenting the current bpf interface, how to use
> it,  drawbacks, todos, ... in that forum?
>
> David Rientjes, who organizes this meeting, is already on Cc.

If we do this, would like an invite to it also!

Have been meaning to take a look into this in detail while in RFC but more so
now obviously :) as discussed in THP cabal, I am broadly in favour of this as
long we get the interface right.

Anyway let me have a look through...!

Cheers, Lorenzo