Re: [PATCH] mm, memcg: support memory.{min, low} protection in cgroup v1

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

On Fri, Jul 5, 2019 at 11:11 PM Brian Foster <bfoster@redhat.com> wrote:
>
> cc linux-xfs
>
> On Fri, Jul 05, 2019 at 10:33:04PM +0800, Yafang Shao wrote:
> > On Fri, Jul 5, 2019 at 7:10 PM Michal Hocko <mhocko@kernel.org> wrote:
> > >
> > > On Fri 05-07-19 17:41:44, Yafang Shao wrote:
> > > > On Fri, Jul 5, 2019 at 5:09 PM Michal Hocko <mhocko@kernel.org> wrote:
> > > [...]
> > > > > Why cannot you move over to v2 and have to stick with v1?
> > > > Because the interfaces between cgroup v1 and cgroup v2 are changed too
> > > > much, which is unacceptable by our customer.
> > >
> > > Could you be more specific about obstacles with respect to interfaces
> > > please?
> > >
> >
> > Lots of applications will be changed.
> > Kubernetes, Docker and some other applications which are using cgroup v1,
> > that will be a trouble, because they are not maintained by us.
> >
> > > > It may take long time to use cgroup v2 in production envrioment, per
> > > > my understanding.
> > > > BTW, the filesystem on our servers is XFS, but the cgroup  v2
> > > > writeback throttle is not supported on XFS by now, that is beyond my
> > > > comprehension.
> > >
> > > Are you sure? I would be surprised if v1 throttling would work while v2
> > > wouldn't. As far as I remember it is v2 writeback throttling which
> > > actually works. The only throttling we have for v1 is reclaim based one
> > > which is a huge hammer.
> > > --
> >
> > We did it in cgroup v1 in our kernel.
> > But the upstream still don't support it in cgroup v2.
> > So my real question is why upstream can't support such an import file system ?
> > Do you know which companies  besides facebook are using cgroup v2  in
> > their product enviroment?
> >
>
> I think the original issue with regard to XFS cgroupv2 writeback
> throttling support was that at the time the XFS patch was proposed,
> there wasn't any test coverage to prove that the code worked (and the
> original author never followed up). That has since been resolved and
> Christoph has recently posted a new patch [1], which appears to have
> been accepted by the maintainer.
>
> Brian
>
> [1] https://marc.info/?l=linux-xfs&m=156138379906141&w=2
>

Thanks for your reference.
I will pay attention to that thread.