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

[Yafang Shao <laoar.shao@gmail.com>]

On Tue, Aug 26, 2025 at 4:33 PM Lorenzo Stoakes
<lorenzo.stoakes@oracle.com> wrote:
>
> 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...!

Thanks in advance.

-- 
Regards
Yafang