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

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Message-ID: <f2edf788-6ff3-43b1-9445-ac237e7910ac@gmail.com>
Date: Tue, 23 Apr 2024 21:21:31 +0200
From: Klara Modin <klarasmodin@...il.com>
To: Xiu Jianfeng <xiujianfeng@...wei.com>, longman@...hat.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

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.

>   	.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
View attachment "bisect-bad-cpu-util" of type "text/plain" (4229 bytes)

View attachment "0001-cgroup-cpuset-fix-bitwise-shift-in-top_cpuset-initia.patch" of type "text/x-patch" (1065 bytes)