netdev - Re: [PATCH v2] net: use bulk free in kfree_skb

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Message-ID: <b33625370d39453edf8f981aef13a7a18a747b0a.camel@redhat.com>
Date:   Mon, 25 Mar 2019 09:54:14 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Felix Fietkau <nbd@....name>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, brouer@...hat.com, fw@...len.de
Subject: Re: [PATCH v2] net: use bulk free in kfree_skb_list

Hi,

On Sun, 2019-03-24 at 17:56 +0100, Felix Fietkau wrote:
> Since we're freeing multiple skbs, we might as well use bulk free to save a
> few cycles. Use the same conditions for bulk free as in napi_consume_skb.
> 
> Signed-off-by: Felix Fietkau <nbd@....name>
> ---
> v2: call kmem_cache_free_bulk once the skb array is full instead of
>     falling back to kfree_skb
>  net/core/skbuff.c | 40 ++++++++++++++++++++++++++++++++++++----
>  1 file changed, 36 insertions(+), 4 deletions(-)
> 
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 2415d9cb9b89..1eeaa264d2a4 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -666,12 +666,44 @@ EXPORT_SYMBOL(kfree_skb);
>  
>  void kfree_skb_list(struct sk_buff *segs)
>  {
> -	while (segs) {
> -		struct sk_buff *next = segs->next;
> +	struct sk_buff *next = segs;
> +	void *skbs[16];
> +	int n_skbs = 0;
>  
> -		kfree_skb(segs);
> -		segs = next;
> +	while ((segs = next) != NULL) {
> +		next = segs->next;
> +
> +		if (!skb_unref(segs))
> +			continue;
> +
> +		if (fclone != SKB_FCLONE_UNAVAILABLE) {
> +			kfree_skb(segs);
> +			continue;
> +		}

I think you should swap the order of skb_unref() and the above check,
or skbs with 'fclone != SKB_FCLONE_UNAVAILABLE' will go twice in
skb_unref() (kfree_skb() calls skb_unref(), too).

Other than that LGTM,

Thanks,

Paolo