linux-kernel - Re: [RFC 08/14] fork: separate vmap stack alloction and free calls

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Date: Sun, 17 Mar 2024 15:51:54 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Pasha Tatashin <pasha.tatashin@...een.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, akpm@...ux-foundation.org, x86@...nel.org, bp@...en8.de,
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 dave.hansen@...ux.intel.com, dianders@...omium.org,
 dietmar.eggemann@....com, eric.devolder@...cle.com, hca@...ux.ibm.com,
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Subject: Re: [RFC 08/14] fork: separate vmap stack alloction and free calls

Le 11/03/2024 à 17:46, Pasha Tatashin a écrit :
> In preparation for the dynamic stacks, separate out the
> __vmalloc_node_range and vfree calls from the vmap based stack
> allocations. The dynamic stacks will use their own variants of these
> functions.
> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> ---
>   kernel/fork.c | 53 ++++++++++++++++++++++++++++++---------------------
>   1 file changed, 31 insertions(+), 22 deletions(-)
> 
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 3004e6ce6c65..bbae5f705773 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -204,6 +204,29 @@ static bool try_release_thread_stack_to_cache(struct vm_struct *vm_area)
>   	return false;
>   }
>   
> +static inline struct vm_struct *alloc_vmap_stack(int node)
> +{
> +	void *stack;
> +
> +	/*
> +	 * Allocated stacks are cached and later reused by new threads,
> +	 * so memcg accounting is performed manually on assigning/releasing
> +	 * stacks to tasks. Drop __GFP_ACCOUNT.
> +	 */
> +	stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
> +				     VMALLOC_START, VMALLOC_END,
> +				     THREADINFO_GFP & ~__GFP_ACCOUNT,
> +				     PAGE_KERNEL,
> +				     0, node, __builtin_return_address(0));
> +
> +	return (stack) ? find_vm_area(stack) : NULL;

Nit: superfluous ()

> +}

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