Re: [PATCH v2 0/4] cgroup/cpuset: Improve CPU isolation in isolated partitions

[Waiman Long]

On 11/9/23 04:02, Zhang, Rui wrote:
> Hi, Waiman,
>
> May I know which kernel this patch series is based on?
>
> I'd like to test this feature, but cannot apply it cleanly on top of
> v6.6.

It was originally based on the cgroup/for-6.7 branch. It should be 
applicable to v6.7 kernel now.

Cheers,
Longman

> thanks,
> rui
>
> On Wed, 2023-10-25 at 14:25 -0400, Waiman Long wrote:
> > v2:
> >   - Add 2 read-only workqueue sysfs files to expose the user requested
> >     cpumask as well as the isolated CPUs to be excluded from
> >     wq_unbound_cpumask.
> >   - Ensure that caller of the new workqueue_unbound_exclude_cpumask()
> >     hold cpus_read_lock.
> >   - Update the cpuset code to make sure the cpus_read_lock is held
> >     whenever workqueue_unbound_exclude_cpumask() may be called.
> >
> > Isolated cpuset partition can currently be created to contain an
> > exclusive set of CPUs not used in other cgroups and with load
> > balancing
> > disabled to reduce interference from the scheduler.
> >
> > The main purpose of this isolated partition type is to dynamically
> > emulate what can be done via the "isolcpus" boot command line option,
> > specifically the default domain flag. One effect of the "isolcpus"
> > option
> > is to remove the isolated CPUs from the cpumasks of unbound
> > workqueues
> > since running work functions in an isolated CPU can be a major source
> > of interference. Changing the unbound workqueue cpumasks can be done
> > at
> > run time by writing an appropriate cpumask without the isolated CPUs
> > to
> > /sys/devices/virtual/workqueue/cpumask. So one can set up an isolated
> > cpuset partition and then write to the cpumask sysfs file to achieve
> > similar level of CPU isolation. However, this manual process can be
> > error prone.
> >
> > This patch series implements automatic exclusion of isolated CPUs
> > from
> > unbound workqueue cpumasks when an isolated cpuset partition is
> > created
> > and then adds those CPUs back when the isolated partition is
> > destroyed.
> >
> > There are also other places in the kernel that look at the
> > HK_FLAG_DOMAIN
> > cpumask or other HK_FLAG_* cpumasks and exclude the isolated CPUs
> > from
> > certain actions to further reduce interference. CPUs in an isolated
> > cpuset partition will not be able to avoid those interferences yet.
> > That
> > may change in the future as the need arises.
> >
> > Waiman Long (4):
> >    workqueue: Add workqueue_unbound_exclude_cpumask() to exclude CPUs
> >      from wq_unbound_cpumask
> >    selftests/cgroup: Minor code cleanup and reorganization of
> >      test_cpuset_prs.sh
> >    cgroup/cpuset: Keep track of CPUs in isolated partitions
> >    cgroup/cpuset: Take isolated CPUs out of workqueue unbound cpumask
> >
> >   Documentation/admin-guide/cgroup-v2.rst       |  10 +-
> >   include/linux/workqueue.h                     |   2 +-
> >   kernel/cgroup/cpuset.c                        | 286 +++++++++++++---
> > --
> >   kernel/workqueue.c                            |  91 +++++-
> >   .../selftests/cgroup/test_cpuset_prs.sh       | 216 ++++++++-----
> >   5 files changed, 438 insertions(+), 167 deletions(-)