Date:   Wed, 8 Feb 2023 18:29:56 +0100
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Kairui Song <kasong@tencent.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Chengming Zhou <zhouchengming@bytedance.com>,
        Tejun Heo <tj@kernel.org>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, Kairui Song <ryncsn@gmail.com>
Subject: Re: [PATCH 2/2] sched/psi: iterate through cgroups directly
Message-ID: <20230208172956.GF24523@blackbody.suse.cz>
References: <20230208161654.99556-1-ryncsn@gmail.com>
 <20230208161654.99556-3-ryncsn@gmail.com>
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On Thu, Feb 09, 2023 at 12:16:54AM +0800, Kairui Song <ryncsn@gmail.com> wrote:
> Signed-off-by: Kairui Song <kasong@tencent.com>
> Signed-off-by: Kairui Song <ryncsn@gmail.com>

Typo?

> -static inline struct psi_group *task_psi_group(struct task_struct *task)
> +static inline struct psi_group *psi_iter_first(struct task_struct *task, void **iter)
>  {
>  #ifdef CONFIG_CGROUPS
> -	if (static_branch_likely(&psi_cgroups_enabled))
> -		return cgroup_psi(task_dfl_cgroup(task));
> +	if (static_branch_likely(&psi_cgroups_enabled)) {
> +		struct cgroup *cgroup = task_dfl_cgroup(task);
> +
> +		*iter = cgroup_parent(cgroup);

This seems to skip a cgroup level -- maybe that's the observed
performance gain?

> +		return cgroup_psi(cgroup);
> +	}
>  #endif
>  	return &psi_system;
>  }

Michal

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