Re: [RFC 0/4] Introduce unbalance proactive reclaim

[Huan Yang]

在 2023/11/8 16:59, Yosry Ahmed 写道:
> On Wed, Nov 8, 2023 at 12:26 AM Huan Yang <link@xxxxxxxx> wrote:
> > 在 2023/11/8 16:00, Yosry Ahmed 写道:
> > > +Wei Xu +David Rientjes
> > >
> > > On Tue, Nov 7, 2023 at 10:59 PM Huan Yang <link@xxxxxxxx> wrote:
> > > > In some cases, we need to selectively reclaim file pages or anonymous
> > > > pages in an unbalanced manner.
> > > >
> > > > For example, when an application is pushed to the background and frozen,
> > > > it may not be opened for a long time, and we can safely reclaim the
> > > > application's anonymous pages, but we do not want to touch the file pages.
> > > >
> > > > This patchset extends the proactive reclaim interface to achieve
> > > > unbalanced reclamation. Users can control the reclamation tendency by
> > > > inputting swappiness under the original interface. Specifically, users
> > > > can input special values to extremely reclaim specific pages.
> > > I proposed this a while back:
> > >
> > > https://lore.kernel.org/linux-mm/CAJD7tkbDpyoODveCsnaqBBMZEkDvshXJmNdbk51yKSNgD7aGdg@xxxxxxxxxxxxxx/
> > Well to know this, proactive reclaim single type is usefull in our
> > production too.
> > > The takeaway from the discussion was that swappiness is not the right
> > > way to do this. We can add separate arguments to specify types of
> > > memory to reclaim, as Roman suggested in that thread. I had some
> > > patches lying around to do that at some point, I can dig them up if
> > > that's helpful, but they are probably based on a very old kernel now,
> > > and before MGLRU landed. IIRC it wasn't very difficult, I think I
> > > added anon/file/shrinkers bits to struct scan_control and then plumbed
> > > them through to memory.reclaim.
> > >
> > > > Example:
> > > >           echo "1G" 200 > memory.reclaim (only reclaim anon)
> > > >             echo "1G" 0  > memory.reclaim (only reclaim file)
> > > >             echo "1G" 1  > memory.reclaim (only reclaim file)
> > > The type of interface here is nested-keyed, so if we add arguments
> > > they need to be in key=value format. Example:
> > >
> > > echo 1G swappiness=200 > memory.reclaim
> > Yes, this is better.
> > > As I mentioned above though, I don't think swappiness is the right way
> > > of doing this. Also, without swappiness, I don't think there's a v1 vs
> > > v2 dilemma here. memory.reclaim can work as-is in cgroup v1, it just
> > > needs to be exposed there.
> > Cgroupv1 can't use memory.reclaim, so, how to exposed it? Reclaim this by
> > pass memcg's ID?
> That was mainly about the idea that cgroup v2 does not have per-memcg
> swappiness, so this proposal seems to be inclined towards v1, at least
I seem current comments of mem_cgroup_swappiness it is believed that
per-memcg swappiness can be added.

But, we first need to explain that using swappiness is a very useful way.
And in the discussions of your patchset, end that not use it.
> conceptually. Either way, we need to add memory.reclaim to the v1
> files to get it to work on v1. Whether this is acceptable or not is up
> to the maintainers. I personally don't think it's a problem, it should
Yes, but, I understand that cgroup v2 is a trend, so it is 
understandable that no
new interfaces are added to v1. :)
Maybe you can promoting the use of cgroupv2 on Android?
> work as-is for v1.