lkml.org 
[lkml]   [2023]   [Sep]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 1/1] cgroup/cpuset: Rebuild sched domains if isolated partition changed
From
Hello Longman,

On 9/17/23 18:51, Waiman Long wrote:
> On 9/15/23 11:45, Pierre Gondois wrote:
>> When an isolated parition is created, the sched domains (sds) are
>> rebuilt and the sds of the isolated CPUs are detached. This only
>> happens at the creation of the isolated parition. Updating
>> the cpuset of the partition doesn't rebuild the sds:
>>
>> To reproduce:
>> # ls /sys/kernel/debug/sched/domains/cpu0/
>> domain0
>> # ls /sys/kernel/debug/sched/domains/cpu1/
>> domain0
>> #
>> # mkdir cgroup
>> # mount -t cgroup2 none cgroup/
>> # mkdir cgroup/A1/
>> # echo "+cpuset" > cgroup/cgroup.subtree_control
>> # echo 0-3 > cgroup/A1/cpuset.cpus
>> # echo isolated > cgroup/A1/cpuset.cpus.partition
>> #
>> # ls /sys/kernel/debug/sched/domains/cpu0/
>> # ls /sys/kernel/debug/sched/domains/cpu1/
>> #
>> # echo 0 > cgroup/A1/cpuset.cpus
>> # ls /sys/kernel/debug/sched/domains/cpu0/
>> # ls /sys/kernel/debug/sched/domains/cpu1/
>> #
>>
>> Here CPU1 should have a sched domain re-attached.
>>
>> Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
>> ---
>> kernel/cgroup/cpuset.c | 12 ++++++++----
>> 1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index 58e6f18f01c1..e3eb27ff9b68 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -1680,11 +1680,15 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
>> * empty cpuset is changed, we need to rebuild sched domains.
>> * On default hierarchy, the cpuset needs to be a partition
>> * root as well.
>> + * Also rebuild sched domains if the cpuset of an isolated
>> + * partition changed.
>> */
>> - if (!cpumask_empty(cp->cpus_allowed) &&
>> - is_sched_load_balance(cp) &&
>> - (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
>> - is_partition_valid(cp)))
>> + if ((!cpumask_empty(cp->cpus_allowed) &&
>> + is_sched_load_balance(cp) &&
>> + (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
>> + is_partition_valid(cp))) ||
>> + (cp->partition_root_state == PRS_ISOLATED ||
>> + cp->partition_root_state == PRS_INVALID_ISOLATED))
>> need_rebuild_sched_domains = true;
>>
>> rcu_read_lock();
>
> Thanks for spotting the problem and sending out a patch to fix it.
> However, it should be done in the update_cpumask(). The sched_domain
> rebuild in update_cpumasks_hier() is supposed to be used for impacted
> descendant cpusets lower down in the hierarchy.
>
> Anyway, I believe this problem should have been fixed in commit
> a86ce68078b2 ("cgroup/cpuset: Extract out CS_CPU_EXCLUSIVE &
> CS_SCHED_LOAD_BALANCE handling") recently merged into the v6.6 kernel.
> Would you mind testing the latest upstream kernel to see if this problem
> is gone or not?

Yes right, v6.6-rc2 kernel doesn't have this issue. My bad for not updating
it ...

However I think the second issue described in the cover letter can still be
reproduced on v6.6-rc2. This present patch was not aiming to fix it though.

Commands:
# mkdir cgroup
# mount -t cgroup2 none cgroup/
# mkdir cgroup/A1 cgroup/B1
# echo "+cpuset" > cgroup/cgroup.subtree_control
# echo 0-3 > cgroup/A1/cpuset.cpus
# echo isolated > cgroup/A1/cpuset.cpus.partition
# echo 4-6 > cgroup/B1/cpuset.cpus
# cat cgroup/A1/cpuset.cpus.partition
isolated
# echo 0-4 > cgroup/A1/cpuset.cpus
# cat cgroup/A1/cpuset.cpus.partition
isolated invalid (Cpu list in cpuset.cpus not exclusive)
# echo 0-3 > cgroup/A1/cpuset.cpus
# cat cgroup/A1/cpuset.cpus.partition
isolated invalid (Cpu list in cpuset.cpus not exclusive)

Cgroup A1 should be a valid isolated partition once its CPUs become
exclusive again I believe,

Regards,
Pierre

>
> Thanks,
> Longman
>

\
 
 \ /
  Last update: 2023-09-18 09:09    [W:0.050 / U:1.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site