We in the linuxCNC community would not be in favour of removing isolcpus.
In our application there are only one or sometimes two RT threads, a
large user base deployed on a variety of platforms.
isolcpus gives our users a simple way to optionally improve RT performance.
When I review the cpusets documentation, it adds additional complexity
to configuration.
Our users are machinists, not IT professionals so would likely
struggle to configure a cpusets environment.
The LinuxCNC application is deployed on machine controllers so boot
time parameters are not an issue and likely preferred.
It would be appreciated if you could consult more widely before
removing isolcpus as it will affect our users
scattered through every country in the world.
Rod Webster
1300 896 832
+61 435 765 611
VMN®
www.vmn.com.au
Rod Webster
1300 896 832
+61 435 765 611
VMN®
www.vmn.com.au
Sole Queensland Distributor
On Thu, 28 Sept 2023 at 18:39, Sebastian Andrzej Siewior
<bigeasy@xxxxxxxxxxxxx> wrote:
>
> On 2023-09-26 12:45:14 [-0400], Joseph Salisbury wrote:
> > Hi All,
> Hi,
>
> > I have a question regarding the isolcpus parameter. I've been seeing this
> > parameter commonly used. However, in the kernel.org documentation[0],
> > isolcpus is listed as depreciated.
> >
> > Is it the case that isolcpus should not be used at all? I've seen it used
> > in conjunction with taskset. However, should we now be telling rt users to
> > use only cpusets in cgroups? I see that CPUAffinity can be set in
> > /etc/systemd/system.conf. Is that the preferred method, so the process
> > scheduler will automatically migrate processes between the cpusets in the
> > cgroup cpuset or the list set by CPUAffinity?
>
> Frederic might know if there is an actual timeline to remove it. The
> suggestions since then is to use cpusets which should be more flexible.
> There was also some work (which went into v6.1 I think) to be able to
> reconfigure the partitions at run-time while isolcpus= is a boot time
> option.
> From what I remember, you have a default/system cpuset which all tasks
> use by default and then you can add another cpuset for the "isolated"
> CPUs. Based on the partition it can be either the default one or
> isolated [0]. The latter would exclude the CPUs from load balancing
> which is what isolcpus= does.
>
> [0] f28e22441f353 ("cgroup/cpuset: Add a new isolated cpus.partition type")
>
> > Thanks,
> >
> > Joe
>
> Sebastian
>
