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

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Message-ID: <98bea19ca5eb5c19ef0ea55f5167237cc841fe9b.camel@intel.com>
Date:   Thu, 9 Nov 2023 09:02:21 +0000
From:   "Zhang, Rui" <rui.zhang@...el.com>
To:     "shuah@...nel.org" <shuah@...nel.org>,
        "longman@...hat.com" <longman@...hat.com>,
        "lizefan.x@...edance.com" <lizefan.x@...edance.com>,
        "hannes@...xchg.org" <hannes@...xchg.org>,
        "tj@...nel.org" <tj@...nel.org>, "corbet@....net" <corbet@....net>,
        "jiangshanlai@...il.com" <jiangshanlai@...il.com>
CC:     "pehunt@...hat.com" <pehunt@...hat.com>,
        "frederic@...nel.org" <frederic@...nel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v2 0/4] cgroup/cpuset: Improve CPU isolation in isolated
 partitions

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.

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(-)
>