Re: [PATCH 6.1 0/2] io_uring/io-wq: respect cgroup cpusets

[MOESSBAUER, Felix]

On Mon, 2024-09-30 at 21:15 +0200, Greg KH wrote:
> On Wed, Sep 11, 2024 at 06:23:14PM +0200, Felix Moessbauer wrote:
> > Hi,
> > 
> > as discussed in [1], this is a manual backport of the remaining two
> > patches to let the io worker threads respect the affinites defined
> > by
> > the cgroup of the process.
> > 
> > In 6.1 one worker is created per NUMA node, while in da64d6db3bd3
> > ("io_uring: One wqe per wq") this is changed to only have a single
> > worker.
> > As this patch is pretty invasive, Jens and me agreed to not
> > backport it.
> > 
> > Instead we now limit the workers cpuset to the cpus that are in the
> > intersection between what the cgroup allows and what the NUMA node
> > has.
> > This leaves the question what to do in case the intersection is
> > empty:
> > To be backwarts compatible, we allow this case, but restrict the
> > cpumask
> > of the poller to the cpuset defined by the cgroup. We further
> > believe
> > this is a reasonable decision, as da64d6db3bd3 drops the NUMA
> > awareness
> > anyways.
> > 
> > [1]
> > https://lore.kernel.org/lkml/ec01745a-b102-4f6e-abc9-abd636d36319@xxxxxxxxx
> 
> Why was neither of these actually tagged for inclusion in a stable
> tree?

This is a manual backport of these patches for 6.1, as the subsystem
changed significantly between 6.1 and 6.2, making an automated backport
impossible. This has been agreed on with Jens in
https://lore.kernel.org/lkml/ec01745a-b102-4f6e-abc9-abd636d36319@xxxxxxxxx/

> Why just 6.1.y?  Please submit them for all relevent kernel versions.

The original patch was tagged stable and got accepted in 6.6, 6.10 and
6.11.

Felix

> 
> thanks,
> 
> greg k-h

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