linux-kernel - Re: [PATCH -next] cgroup/cpuset: Statically initialize more members of top

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Message-ID: <a583d400-ed59-46b8-a26d-b726055b5cad@redhat.com>
Date: Tue, 23 Apr 2024 15:50:31 -0400
From: Waiman Long <longman@...hat.com>
To: Klara Modin <klarasmodin@...il.com>, Xiu Jianfeng
 <xiujianfeng@...wei.com>, lizefan.x@...edance.com, tj@...nel.org,
 hannes@...xchg.org
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] cgroup/cpuset: Statically initialize more members
 of top_cpuset


On 4/23/24 15:21, Klara Modin wrote:
> Hi,
>
> On 2024-04-20 11:46, Xiu Jianfeng wrote:
>> Initializing top_cpuset.relax_domain_level and setting
>> CS_SCHED_LOAD_BALANCE to top_cpuset.flags in cpuset_init() could be
>> completed at the time of top_cpuset definition by compiler.
>>
>> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>
>> ---
>>   kernel/cgroup/cpuset.c | 5 ++---
>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index d8d3439eda4e..e70008a1d86a 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -369,8 +369,9 @@ static inline void notify_partition_change(struct 
>> cpuset *cs, int old_prs)
>>     static struct cpuset top_cpuset = {
>>       .flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
>> -          (1 << CS_MEM_EXCLUSIVE)),
>> +          (1 << CS_MEM_EXCLUSIVE) | (1 < CS_SCHED_LOAD_BALANCE)),
>
> You dropped a '<' for the bitwise shift, this causes bad cpu 
> utilization for me.

Oh, now load_balancing is disable by default in the root cgroup. That is 
bad. Will post a patch to fix it.

Thanks,
Longman



>
>>       .partition_root_state = PRS_ROOT,
>> +    .relax_domain_level = -1,
>>       .remote_sibling = LIST_HEAD_INIT(top_cpuset.remote_sibling),
>>   };
>>   @@ -4309,8 +4310,6 @@ int __init cpuset_init(void)
>>       nodes_setall(top_cpuset.effective_mems);
>>         fmeter_init(&top_cpuset.fmeter);
>> -    set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
>> -    top_cpuset.relax_domain_level = -1;
>>       INIT_LIST_HEAD(&remote_children);
>>         BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL));
>
> Kind regards,
> Klara Modin