From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Daniel Bristot de Oliveira <bristot@redhat.com>,
linux-kernel@vger.kernel.org
Cc: Marco Perronet <perronet@mpi-sws.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
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 4/6] sched/deadline: Block DL tasks on non-exclusive cpuset if bandwitdh control is enable
Date: Thu, 14 Jan 2021 16:51:43 +0100 [thread overview]
Message-ID: <4b37b32b-0e16-ffbc-ca6a-fbee935c0813@arm.com> (raw)
In-Reply-To: <7b336c37cc3c38def6de181df8ba8c3148c5cc0c.1610463999.git.bristot@redhat.com>
On 12/01/2021 16:53, Daniel Bristot de Oliveira wrote:
> The current SCHED_DEADLINE design supports only global scheduler,
> or variants of it, i.e., clustered and partitioned, via cpuset config.
> To enable the partitioning of a system with clusters of CPUs, the
> documentation advises the usage of exclusive cpusets, creating an
> exclusive root_domain for the cpuset.
>
> Attempts to change the cpu affinity of a thread to a cpu mask different
> from the root domain results in an error. For instance:
[...]
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 788a391657a5..c221e14d5b86 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2878,6 +2878,13 @@ int dl_task_can_attach(struct task_struct *p,
> if (cpumask_empty(cs_cpus_allowed))
> return 0;
>
> + /*
> + * Do not allow moving tasks to non-exclusive cpusets
> + * if bandwidth control is enabled.
> + */
> + if (dl_bandwidth_enabled() && !exclusive)
> + return -EBUSY;
> +
> /*
> * The task is not moving to another root domain, so it is
> * already accounted.
>
But doesn't this mean you only have to set this cgroup exclusive/root to
run into the same issue:
with this patch:
cgroupv1:
root@juno:/sys/fs/cgroup/cpuset# chrt -d --sched-period 1000000000
--sched-runtime 100000000 0 sleep 500 &
[1] 1668
root@juno:/sys/fs/cgroup/cpuset# PID1=$!
root@juno:/sys/fs/cgroup/cpuset# chrt -d --sched-period 1000000000
--sched-runtime 100000000 0 sleep 500 &
[2] 1669
root@juno:/sys/fs/cgroup/cpuset# PID2=$!
root@juno:/sys/fs/cgroup/cpuset# mkdir A
root@juno:/sys/fs/cgroup/cpuset# echo 0 > ./A/cpuset.mems
root@juno:/sys/fs/cgroup/cpuset# echo 0 > ./A/cpuset.cpus
root@juno:/sys/fs/cgroup/cpuset# echo $PID2 > ./A/cgroup.procs
-bash: echo: write error: Device or resource busy
root@juno:/sys/fs/cgroup/cpuset# echo 1 > ./A/cpuset.cpu_exclusive
root@juno:/sys/fs/cgroup/cpuset# echo $PID2 > ./A/cgroup.procs
root@juno:/sys/fs/cgroup/cpuset# cat /proc/$PID1/status | grep
Cpus_allowed_list | awk '{print $2}'
0-5
root@juno:/sys/fs/cgroup/cpuset# cat /proc/$PID2/status | grep
Cpus_allowed_list | awk '{print $2}'
0
cgroupv2:
root@juno:/sys/fs/cgroup# echo +cpuset > cgroup.subtree_control
root@juno:/sys/fs/cgroup# chrt -d --sched-period 1000000000
--sched-runtime 100000000 0 sleep 500 &
[1] 1687
root@juno:/sys/fs/cgroup# PID1=$!
root@juno:/sys/fs/cgroup# chrt -d --sched-period 1000000000
--sched-runtime 100000000 0 sleep 500 &
[2] 1688
root@juno:/sys/fs/cgroup# PID2=$!
root@juno:/sys/fs/cgroup# mkdir A
root@juno:/sys/fs/cgroup# echo 0 > ./A/cpuset.mems
root@juno:/sys/fs/cgroup# echo 0 > ./A/cpuset.cpus
root@juno:/sys/fs/cgroup# echo $PID2 > ./A/cgroup.procs
-bash: echo: write error: Device or resource busy
root@juno:/sys/fs/cgroup# echo root > ./A/cpuset.cpus.partition
root@juno:/sys/fs/cgroup# echo $PID2 > ./A/cgroup.procs
root@juno:/sys/fs/cgroup# cat /proc/$PID1/status | grep
Cpus_allowed_list | awk '{print $2}'
0-5
root@juno:/sys/fs/cgroup# cat /proc/$PID2/status | grep
Cpus_allowed_list | awk '{print $2}'
0
next prev parent reply other threads:[~2021-01-14 15:52 UTC|newest]
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
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 [this message]
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
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