linux-kernel - Re: [PATCH] mm: memcontrol: fix kernel stack account

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Message-ID: <YD6I+DLH0SLnSgo8@carbon.dhcp.thefacebook.com>
Date:   Tue, 2 Mar 2021 10:50:32 -0800
From:   Roman Gushchin <guro@...com>
To:     Muchun Song <songmuchun@...edance.com>
CC:     <hannes@...xchg.org>, <mhocko@...nel.org>,
        <akpm@...ux-foundation.org>, <shakeelb@...gle.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: memcontrol: fix kernel stack account

On Tue, Mar 02, 2021 at 03:37:33PM +0800, Muchun Song wrote:
> The alloc_thread_stack_node() cannot guarantee that allocated stack pages
> are in the same node when CONFIG_VMAP_STACK. Because we do not specify
> __GFP_THISNODE to __vmalloc_node_range(). Fix it by caling
> mod_lruvec_page_state() for each page one by one.

Hm, I actually wonder if it makes any sense to split the stack over multiple
nodes? Maybe we should fix this instead?

> 
> Fixes: 991e7673859e ("mm: memcontrol: account kernel stack per node")
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> ---
>  kernel/fork.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/fork.c b/kernel/fork.c
> index d66cd1014211..6e2201feb524 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -379,14 +379,19 @@ static void account_kernel_stack(struct task_struct *tsk, int account)
>  	void *stack = task_stack_page(tsk);
>  	struct vm_struct *vm = task_stack_vm_area(tsk);
>  
> +	if (vm) {
> +		int i;
>  
> -	/* All stack pages are in the same node. */
> -	if (vm)
> -		mod_lruvec_page_state(vm->pages[0], NR_KERNEL_STACK_KB,
> -				      account * (THREAD_SIZE / 1024));
> -	else
> +		BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
> +
> +		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
> +			mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
> +					      account * (PAGE_SIZE / 1024));
> +	} else {
> +		/* All stack pages are in the same node. */
>  		mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
>  				      account * (THREAD_SIZE / 1024));
> +	}
>  }
>  
>  static int memcg_charge_kernel_stack(struct task_struct *tsk)
> -- 
> 2.11.0
>