LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Juri Lelli <juri.lelli@redhat.com>
To: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: linux-kernel@vger.kernel.org,
	Marco Perronet <perronet@mpi-sws.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Li Zefan <lizefan@huawei.com>, Tejun Heo <tj@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	cgroups@vger.kernel.org
Subject: Re: [PATCH 3/6] sched/deadline: Allow DL tasks on empty (cgroup v2) cpusets
Date: Fri, 22 Jan 2021 09:08:51 +0100
Message-ID: <20210122080851.GK10569@localhost.localdomain> (raw)
In-Reply-To: <8380113688bd64a6deb3241ff6a0fff62b157f47.1610463999.git.bristot@redhat.com>

Hi,

On 12/01/21 16:53, Daniel Bristot de Oliveira wrote:
> cgroups v2 allows the cpuset controller to be enabled/disabled on
> demand. On Fedora 32, cpuset is disabled by default. To enable it,
> a user needs to:
> 
>   # cd /sys/fs/cgroup/
>   # echo +cpuset > cgroup.subtree_control
> 
> Existing cgroups will expose the cpuset interface (e.g., cpuset.cpus
> file). By default, cpuset.cpus has no CPU assigned, which means that
> existing tasks will move to a cpuset without cpus.

This is kind of confusing, though. Isn't it?

> Initially, I thought about returning an error and blocking the
> operation. However, that is indeed not needed. The cpuset without
> CPUs assigned will be a non-root cpuset, hence its cpu mask will
> be the same as the root one. So, the bandwidth was already accounted,
> and the task can proceed.
> 
> Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
> Cc: Li Zefan <lizefan@huawei.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Valentin Schneider <valentin.schneider@arm.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: cgroups@vger.kernel.org
> ---
>  kernel/sched/deadline.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 943aa32cc1bc..788a391657a5 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2871,6 +2871,13 @@ int dl_task_can_attach(struct task_struct *p,
>  	bool overflow;
>  	int ret;
>  
> +	/*
> +	 * The cpuset has no cpus assigned, so the thread will not
> +	 * change its affinity.

Is this always the case also in the presence of deeper hierarchies?

Thanks,
Juri


  parent reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-12 15:53 [PATCH 0/6] sched/deadline: cpuset task acceptance review Daniel Bristot de Oliveira
2021-01-12 15:53 ` [PATCH 1/6] sched/deadline: Consolidate the SCHED_DL task_can_attach() check on its own function Daniel Bristot de Oliveira
2021-01-12 15:53 ` [PATCH 2/6] sched/deadline: Inform dl_task_can_attach() if the cpuset is exclusive Daniel Bristot de Oliveira
2021-01-12 15:53 ` [PATCH 3/6] sched/deadline: Allow DL tasks on empty (cgroup v2) cpusets Daniel Bristot de Oliveira
2021-01-14 12:12   ` Dietmar Eggemann
2021-01-18 12:51     ` Daniel Bristot de Oliveira
2021-01-22  8:08   ` Juri Lelli [this message]
2021-01-12 15:53 ` [PATCH 4/6] sched/deadline: Block DL tasks on non-exclusive cpuset if bandwitdh control is enable Daniel Bristot de Oliveira
2021-01-14 15:51   ` Dietmar Eggemann
2021-01-19  9:41     ` Daniel Bristot de Oliveira
2021-01-19 15:37       ` Dietmar Eggemann
2021-01-12 15:53 ` [PATCH 5/6] sched/deadline: Add helpers to get the correct root domain/span/dl_bw Daniel Bristot de Oliveira
2021-01-12 15:53 ` [PATCH 6/6] sched/deadline: Fixes cpu/rd/dl_bw references for suspended tasks Daniel Bristot de Oliveira
2021-01-15 14:36   ` Dietmar Eggemann
2021-01-18 13:17     ` Daniel Bristot de Oliveira

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210122080851.GK10569@localhost.localdomain \
    --to=juri.lelli@redhat.com \
    --cc=bristot@redhat.com \
    --cc=bsegall@google.com \
    --cc=cgroups@vger.kernel.org \
    --cc=dietmar.eggemann@arm.com \
    --cc=hannes@cmpxchg.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=lizefan@huawei.com \
    --cc=mgorman@suse.de \
    --cc=mingo@redhat.com \
    --cc=perronet@mpi-sws.org \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=tj@kernel.org \
    --cc=valentin.schneider@arm.com \
    --cc=vincent.guittot@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git
	git clone --mirror https://lore.kernel.org/lkml/10 lkml/git/10.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git