netdev - Re: [PATCH net-next] netlink: use kvmalloc() in netlink_alloc_large

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Date: Mon, 26 Feb 2024 09:33:02 +0800
From: shaozhengchao <shaozhengchao@...wei.com>
To: Eric Dumazet <edumazet@...gle.com>, "David S . Miller"
	<davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: <netdev@...r.kernel.org>, <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next] netlink: use kvmalloc() in
 netlink_alloc_large_skb()



On 2024/2/24 17:06, Eric Dumazet wrote:
> This is a followup of commit 234ec0b6034b ("netlink: fix potential
> sleeping issue in mqueue_flush_file"), because vfree_atomic()
> overhead is unfortunate for medium sized allocations.
> 
> 1) If the allocation is smaller than PAGE_SIZE, do not bother
>     with vmalloc() at all. Some arches have 64KB PAGE_SIZE,
>     while NLMSG_GOODSIZE is smaller than 8KB.
> 
> 2) Use kvmalloc(), which might allocate one high order page
>     instead of vmalloc if memory is not too fragmented.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Zhengchao Shao <shaozhengchao@...wei.com>
> ---
>   net/netlink/af_netlink.c | 18 ++++++++----------
>   1 file changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 9c962347cf859f16fc76e4d8a2fd22cdb3d142d6..90ca4e0ed9b3632bf223bf29fd864dbb76f3c89c 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -1206,23 +1206,21 @@ struct sock *netlink_getsockbyfilp(struct file *filp)
>   
>   struct sk_buff *netlink_alloc_large_skb(unsigned int size, int broadcast)
>   {
> +	size_t head_size = SKB_HEAD_ALIGN(size);
>   	struct sk_buff *skb;
>   	void *data;
>   
> -	if (size <= NLMSG_GOODSIZE || broadcast)
> +	if (head_size <= PAGE_SIZE || broadcast)
>   		return alloc_skb(size, GFP_KERNEL);
>   
> -	size = SKB_DATA_ALIGN(size) +
> -	       SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> -
> -	data = vmalloc(size);
> -	if (data == NULL)
> +	data = kvmalloc(head_size, GFP_KERNEL);
> +	if (!data)
>   		return NULL;
>   
> -	skb = __build_skb(data, size);
> -	if (skb == NULL)
> -		vfree(data);
> -	else
> +	skb = __build_skb(data, head_size);
> +	if (!skb)
> +		kvfree(data);
> +	else if (is_vmalloc_addr(data))
>   		skb->destructor = netlink_skb_destructor;
>   
>   	return skb;
LGTM, thanks.

Reviewed-by: Zhengchao Shao <shaozhengchao@...wei.com>