linux-kernel - Re: [PATCH net-next,1/3] hv_netvsc: Use per socket hash when available

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Date:   Tue, 11 Apr 2017 22:12:41 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     haiyangz@...rosoft.com, haiyangz@...hange.microsoft.com
Cc:     netdev@...r.kernel.org, kys@...rosoft.com, olaf@...fle.de,
        vkuznets@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next,1/3] hv_netvsc: Use per socket hash when
 available

From: Haiyang Zhang <haiyangz@...hange.microsoft.com>
Date: Sat,  8 Apr 2017 17:53:59 -0700

> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index f24c289..0a129cb 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -211,9 +211,14 @@ static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
>  	int q_idx = sk_tx_queue_get(sk);
>  
>  	if (q_idx < 0 || skb->ooo_okay || q_idx >= num_tx_queues) {
> -		u16 hash = __skb_tx_hash(ndev, skb, VRSS_SEND_TAB_SIZE);
> +		u16 hash;
>  		int new_idx;
>  
> +		if (sk)
> +			skb_set_hash_from_sk(skb, sk);
> +
> +		hash = __skb_tx_hash(ndev, skb, VRSS_SEND_TAB_SIZE);

Please do not do this.

TCP performs this operation for you for every pack it emits.

And also every socket family that uses skb_set_owner_w() either
directly or indirectly gets this done as well.

I do not want to see drivers start to get peppered with calls to this
thing.

Explain the case which is missing that matters, and we can address
that instead.

Thanks.