From: Chris Friesen <chris.friesen@windriver.com>
To: Marcelo Tosatti <mtosatti@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, Christoph Lameter <cl@linux.com>,
Jim Somerville <Jim.Somerville@windriver.com>,
Andrew Morton <akpm@linux-foundation.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v2] isolcpus: affine kernel threads to specified cpumask
Date: Tue, 24 Mar 2020 09:56:26 -0600 [thread overview]
Message-ID: <f40c828e-5168-bd08-69b8-f7a54fd53f42@windriver.com> (raw)
In-Reply-To: <20200324152016.GA25422@fuller.cnet>
I hadn't been keeping up with all the changes to the "isolcpus" boot
arg. Given how it's been extended, I agree that it seems the logical
place to deal with this. Patch seems okay to me, but I've got a couple
of nits in the message portion.
If I want to specify both no_kthreads and managed_irq it then something
like "isolcpus=managed_irq,no_kthreads,2-16" would work?
On 3/24/2020 9:20 AM, Marcelo Tosatti wrote:
>
> This is a kernel enhancement to configure the cpu affinity of kernel
> threads via kernel boot option isolcpus=no_kthreads,<isolcpus_params>,<cpulist>
https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.txt
says that "isolcpus" is deprecated. Are we un-deprecating it? Or is it
only really deprecated for the "domain" option?
> When this option is specified, the cpumask is immediately applied upon
> thread launch. This does not affect kernel threads that specify cpu
> and node.
>
> This allows CPU isolation (that is not allowing certain threads
> to execute on certain CPUs) without using the isolcpus=domain parameter,
> making it possible to enable load balancing on such CPUs
> during runtime (see
I think you're missing the rest of the sentence here.
> Note-1: this is based off on Wind River's patch at
> https://github.com/starlingx-staging/stx-integ/blob/master/kernel/kernel-std/centos/patches/affine-compute-kernel-threads.patch
>
> Difference being that this patch is limited to modifying
> kernel thread cpumask: Behaviour of other threads can
> be controlled via cgroups or sched_setaffinity.
>
> Note-2: MontaVista's patch was based off Christoph Lameter's patch at
> https://lwn.net/Articles/565932/ with the only difference being
> the kernel parameter changed from kthread to kthread_cpus.
Wind River, not MontaVista. I know all us embedded linux folks look the
same...
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>
> ---
>
> v2: use isolcpus= subcommand (Thomas Gleixner)
>
> Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++
> include/linux/cpumask.h | 5 +++++
> include/linux/sched/isolation.h | 1 +
> init/main.c | 1 +
> kernel/cpu.c | 13 +++++++++++++
> kernel/kthread.c | 4 ++--
> kernel/sched/isolation.c | 6 ++++++
> 7 files changed, 36 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index c07815d230bc..7318e3057383 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1959,6 +1959,14 @@
> the CPU affinity syscalls or cpuset.
> <cpu number> begins at 0 and the maximum value is
> "number of CPUs in system - 1".
> + When using cpusets, use the isolcpus option no_kthreads
> + to avoid creation of kernel threads on isolated CPUs.
> +
> + no_kthreads
> + Adjust the CPU affinity mask of unbound kernel threads to
> + not contain CPUs on the isolated list. This complements
> + the isolation provided by the cpusets mechanism described
> + above.
It also complements the "managed_irq" option below. In many cases I'd
expect the same set of CPUs to be isolated from both irqs and kernel
threads.
Chris
next prev parent reply other threads:[~2020-03-24 15:56 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-23 13:54 [PATCH] affine kernel threads to specified cpumask Marcelo Tosatti
2020-03-23 15:29 ` Chris Friesen
2020-03-24 15:07 ` Marcelo Tosatti
2020-03-23 16:22 ` Thomas Gleixner
2020-03-23 17:02 ` Chris Friesen
2020-03-23 20:31 ` Thomas Gleixner
2020-03-24 11:38 ` Marcelo Tosatti
2020-03-24 15:20 ` [PATCH v2] isolcpus: " Marcelo Tosatti
2020-03-24 15:56 ` Chris Friesen [this message]
2020-03-24 16:50 ` Marcelo Tosatti
2020-03-25 0:30 ` Frederic Weisbecker
2020-03-25 11:47 ` Marcelo Tosatti
2020-03-26 16:20 ` Frederic Weisbecker
2020-03-26 16:52 ` Frederic Weisbecker
2020-03-27 12:07 ` Marcelo Tosatti
2020-03-25 18:05 ` David Laight
2020-03-26 11:28 ` Marcelo Tosatti
2020-03-26 16:22 ` Frederic Weisbecker
2020-03-26 16:32 ` Chris Friesen
2020-03-26 16:51 ` Frederic Weisbecker
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