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[PATCH net-next] net: lantiq_xrx200: use skb cache

Aleksander Jan Bajkowski posted 1 patch 3 years, 9 months ago
There is a newer version of this series
drivers/net/ethernet/lantiq_xrx200.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
[PATCH net-next] net: lantiq_xrx200: use skb cache
Posted by Aleksander Jan Bajkowski 3 years, 9 months ago 
napi_build_skb() reuses NAPI skbuff_head cache in order to save some
cycles on freeing/allocating skbuff_heads on every new Rx or completed
Tx.
Use napi_consume_skb() to feed the cache with skbuff_heads of completed
Tx. The budget parameter is added to indicate NAPI context, as a value
of zero can be passed in the case of netpoll.

NAT performance results on BT Home Hub 5A (kernel 5.15.45, mtu 1500):

Fast path (Software Flow Offload):
	Up	Down
Before	702.4	719.3
After	707.3	739.9

Slow path:
	Up	Down
Before	91.8	184.1
After	92.0	185.7

Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
---
 drivers/net/ethernet/lantiq_xrx200.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
index 5edb68a8aab1..83e07404803f 100644
--- a/drivers/net/ethernet/lantiq_xrx200.c
+++ b/drivers/net/ethernet/lantiq_xrx200.c
@@ -238,7 +238,7 @@ static int xrx200_hw_receive(struct xrx200_chan *ch)
 		return ret;
 	}
 
-	skb = build_skb(buf, priv->rx_skb_size);
+	skb = napi_build_skb(buf, priv->rx_skb_size);
 	skb_reserve(skb, NET_SKB_PAD);
 	skb_put(skb, len);
 
@@ -321,7 +321,7 @@ static int xrx200_tx_housekeeping(struct napi_struct *napi, int budget)
 			pkts++;
 			bytes += skb->len;
 			ch->skb[ch->tx_free] = NULL;
-			consume_skb(skb);
+			napi_consume_skb(skb, budget);
 			memset(&ch->dma.desc_base[ch->tx_free], 0,
 			       sizeof(struct ltq_dma_desc));
 			ch->tx_free++;
-- 
2.30.2
Re: [PATCH net-next] net: lantiq_xrx200: use skb cache
Posted by Eric Dumazet 3 years, 9 months ago 
On Tue, Jul 12, 2022 at 8:15 PM Aleksander Jan Bajkowski <olek2@wp.pl> wrote:
>
> napi_build_skb() reuses NAPI skbuff_head cache in order to save some
> cycles on freeing/allocating skbuff_heads on every new Rx or completed
> Tx.
> Use napi_consume_skb() to feed the cache with skbuff_heads of completed
> Tx. The budget parameter is added to indicate NAPI context, as a value
> of zero can be passed in the case of netpoll.
>
> NAT performance results on BT Home Hub 5A (kernel 5.15.45, mtu 1500):
>
> Fast path (Software Flow Offload):
>         Up      Down
> Before  702.4   719.3
> After   707.3   739.9
>
> Slow path:
>         Up      Down
> Before  91.8    184.1
> After   92.0    185.7
>
> Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
> ---
>  drivers/net/ethernet/lantiq_xrx200.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
> index 5edb68a8aab1..83e07404803f 100644
> --- a/drivers/net/ethernet/lantiq_xrx200.c
> +++ b/drivers/net/ethernet/lantiq_xrx200.c
> @@ -238,7 +238,7 @@ static int xrx200_hw_receive(struct xrx200_chan *ch)
>                 return ret;
>         }
>
> -       skb = build_skb(buf, priv->rx_skb_size);
> +       skb = napi_build_skb(buf, priv->rx_skb_size);

If you are changing this code path, what about adding proper error recovery ?

skb can be NULL at this point :/


>         skb_reserve(skb, NET_SKB_PAD);
>         skb_put(skb, len);
>
> @@ -321,7 +321,7 @@ static int xrx200_tx_housekeeping(struct napi_struct *napi, int budget)
>                         pkts++;
>                         bytes += skb->len;
>                         ch->skb[ch->tx_free] = NULL;
> -                       consume_skb(skb);
> +                       napi_consume_skb(skb, budget);
>                         memset(&ch->dma.desc_base[ch->tx_free], 0,
>                                sizeof(struct ltq_dma_desc));
>                         ch->tx_free++;
> --
> 2.30.2
>
Re: [PATCH net-next] net: lantiq_xrx200: use skb cache
Posted by Aleksander Bajkowski 3 years, 9 months ago 
Hi Eric,

On 7/13/22 14:50, Eric Dumazet wrote:
> On Tue, Jul 12, 2022 at 8:15 PM Aleksander Jan Bajkowski <olek2@wp.pl> wrote:
>>
>> napi_build_skb() reuses NAPI skbuff_head cache in order to save some
>> cycles on freeing/allocating skbuff_heads on every new Rx or completed
>> Tx.
>> Use napi_consume_skb() to feed the cache with skbuff_heads of completed
>> Tx. The budget parameter is added to indicate NAPI context, as a value
>> of zero can be passed in the case of netpoll.
>>
>> NAT performance results on BT Home Hub 5A (kernel 5.15.45, mtu 1500):
>>
>> Fast path (Software Flow Offload):
>>         Up      Down
>> Before  702.4   719.3
>> After   707.3   739.9
>>
>> Slow path:
>>         Up      Down
>> Before  91.8    184.1
>> After   92.0    185.7
>>
>> Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
>> ---
>>  drivers/net/ethernet/lantiq_xrx200.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
>> index 5edb68a8aab1..83e07404803f 100644
>> --- a/drivers/net/ethernet/lantiq_xrx200.c
>> +++ b/drivers/net/ethernet/lantiq_xrx200.c
>> @@ -238,7 +238,7 @@ static int xrx200_hw_receive(struct xrx200_chan *ch)
>>                 return ret;
>>         }
>>
>> -       skb = build_skb(buf, priv->rx_skb_size);
>> +       skb = napi_build_skb(buf, priv->rx_skb_size);
> 
> If you are changing this code path, what about adding proper error recovery ?
> 
> skb can be NULL at this point :/
> 


Good catch. I will try to test the fix on the device tomorrow and send the patch.

>>         skb_reserve(skb, NET_SKB_PAD);
>>         skb_put(skb, len);
>>
>> @@ -321,7 +321,7 @@ static int xrx200_tx_housekeeping(struct napi_struct *napi, int budget)
>>                         pkts++;
>>                         bytes += skb->len;
>>                         ch->skb[ch->tx_free] = NULL;
>> -                       consume_skb(skb);
>> +                       napi_consume_skb(skb, budget);
>>                         memset(&ch->dma.desc_base[ch->tx_free], 0,
>>                                sizeof(struct ltq_dma_desc));
>>                         ch->tx_free++;
>> --
>> 2.30.2
>>

Best regards,
Aleksander
Re: [PATCH net-next] net: lantiq_xrx200: use skb cache
Posted by Jakub Kicinski 3 years, 9 months ago 
On Wed, 13 Jul 2022 22:38:37 +0200 Aleksander Bajkowski wrote:
> > If you are changing this code path, what about adding proper error recovery ?
> > 
> > skb can be NULL at this point :/
>
> Good catch. I will try to test the fix on the device tomorrow and send the patch.

Let's defer this patch until we merge the fix, otherwise we'll get 
a conflict. Not a big deal but easily avoidable here.
Re: [PATCH net-next] net: lantiq_xrx200: use skb cache
Posted by Hauke Mehrtens 3 years, 9 months ago 
On 7/12/22 20:14, Aleksander Jan Bajkowski wrote:
> napi_build_skb() reuses NAPI skbuff_head cache in order to save some
> cycles on freeing/allocating skbuff_heads on every new Rx or completed
> Tx.
> Use napi_consume_skb() to feed the cache with skbuff_heads of completed
> Tx. The budget parameter is added to indicate NAPI context, as a value
> of zero can be passed in the case of netpoll.
> 
> NAT performance results on BT Home Hub 5A (kernel 5.15.45, mtu 1500):
> 
> Fast path (Software Flow Offload):
> 	Up	Down
> Before	702.4	719.3
> After	707.3	739.9
> 
> Slow path:
> 	Up	Down
> Before	91.8	184.1
> After	92.0	185.7
> 
> Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>

Acked-by: Hauke Mehrtens <hauke@hauke-m.de>

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