Re: [Phishing Risk] [External] Re: [PATCH 2/3] cgroup/cpuset: introduce cpuset.mems.migration

[Abel Wu]

ping :)

On 4/27/21 10:43 PM, Tejun Heo wrote:
> Hello,
>
> On Mon, Apr 26, 2021 at 02:59:45PM +0800, Abel Wu wrote:
> > When a NUMA node is assigned to numa-service, the workload
> > on that node needs to be moved away fast and complete. The
> > main aspects we cared about on the eviction are as follows:
> >
> > a) it should complete soon enough so that numa-services
> >     won’t wait too long to hurt user experience
> > b) the workloads to be evicted could have massive usage on
> >     memory, and migrating such amount of memory may lead to
> >     a sudden severe performance drop lasting tens of seconds
> >     that some certain workloads may not afford
> > c) the impact of the eviction should be limited within the
> >     source and destination nodes
> > d) cgroup interface is preferred
> >
> > So we come to a thought that:
> >
> > 1) fire up numa-services without waiting for memory migration
> > 2) memory migration can be done asynchronously by using spare
> >     memory bandwidth
> >
> > AutoNUMA seems to be a solution, but its scope is global which
> > violates c&d. And cpuset.memory_migrate performs in a synchronous
>
> I don't think d) in itself is a valid requirement. How does it violate c)?
>
> > fashion which breaks a&b. So a mixture of them, the new cgroup2
> > interface cpuset.mems.migration, is introduced.
> >
> > The new cpuset.mems.migration supports three modes:
> >
> >   - "none" mode, meaning migration disabled
> >   - "sync" mode, which is exactly the same as the cgroup v1
> >     interface cpuset.memory_migrate
> >   - "lazy" mode, when walking through all the pages, unlike
> >     cpuset.memory_migrate, it only sets pages to protnone,
> >     and numa faults triggered by later touch will handle the
> >     movement.
>
> cpuset is already involved in NUMA allocation but it always felt like
> something bolted on - it's weird to have cpu to NUMA node settings at global
> level and then to have possibly conflicting direct NUMA configuration via
> cpuset. My preference would be putting as much configuration as possible on
> the mm / autonuma side and let cpuset's node confinements further restrict
> their operations rather than cpuset having its own set of policy
> configurations.
>
> Johannes, what are your thoughts?
>
> Thanks.