diff mbox

[net-next,8/8] stmmac: limit max_mtu in case of 4KiB and use __netdev_alloc_skb.

Message ID 1318932085-14927-9-git-send-email-peppe.cavallaro@st.com
State Superseded, archived
Delegated to: David Miller
Headers show

Commit Message

Giuseppe CAVALLARO Oct. 18, 2011, 10:01 a.m. UTC 
Problem using big mtu around 4096 bytes is you end allocating (4096
+NET_SKB_PAD + NET_IP_ALIGN + sizeof(struct skb_shared_info) bytes ->
8192 bytes : order-1 pages

It's better to limit the mtu to SKB_MAX_HEAD(NET_SKB_PAD),
to have no more than one page per skb.

Also the patch changes the netdev_alloc_skb_ip_align() done in
init_dma_desc_rings() and uses a variant allowing GFP_KERNEL allocations
allowing the driver to load even in case of memory pressure.

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   13 +++++++++----
 1 files changed, 9 insertions(+), 4 deletions(-)

Comments

Eric Dumazet Oct. 18, 2011, 10:18 a.m. UTC | #1 
Le mardi 18 octobre 2011 à 12:01 +0200, Giuseppe CAVALLARO a écrit :
> Problem using big mtu around 4096 bytes is you end allocating (4096
> +NET_SKB_PAD + NET_IP_ALIGN + sizeof(struct skb_shared_info) bytes ->
> 8192 bytes : order-1 pages
> 
> It's better to limit the mtu to SKB_MAX_HEAD(NET_SKB_PAD),
> to have no more than one page per skb.
> 
> Also the patch changes the netdev_alloc_skb_ip_align() done in
> init_dma_desc_rings() and uses a variant allowing GFP_KERNEL allocations
> allowing the driver to load even in case of memory pressure.
> 
> Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
> Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   13 +++++++++----
>  1 files changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 1848a16..f5ca3be 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -474,11 +474,13 @@ static void init_dma_desc_rings(struct net_device *dev)
>  	for (i = 0; i < rxsize; i++) {
>  		struct dma_desc *p = priv->dma_rx + i;
>  
> -		skb = netdev_alloc_skb_ip_align(dev, bfsize);
> +		skb = __netdev_alloc_skb(dev, bfsize + NET_IP_ALIGN,
> +					 GFP_KERNEL);
>  		if (unlikely(skb == NULL)) {
>  			pr_err("%s: Rx init fails; skb is NULL\n", __func__);
>  			break;
>  		}
> +		skb_reserve(skb, NET_IP_ALIGN);
>  		priv->rx_skbuff[i] = skb;
>  		priv->rx_skbuff_dma[i] = dma_map_single(priv->device, skb->data,
>  						bfsize, DMA_FROM_DEVICE);
> @@ -1176,12 +1178,15 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv)
>  
>  			skb = __skb_dequeue(&priv->rx_recycle);
>  			if (skb == NULL)
> -				skb = netdev_alloc_skb_ip_align(priv->dev,
> -								bfsize);
> +				skb = __netdev_alloc_skb(priv->dev, bfsize +
> +							 NET_IP_ALIGN,
> +							 GFP_KERNEL);
>  

No, you cant do that in softirq context. We cant sleep here and must use
GFP_ATOMIC

Only the init_dma_desc_rings() part is OK, we run in process context and
are allowed to sleep in memory allocations (GFP_KERNEL)


>  			if (unlikely(skb == NULL))
>  				break;
>  
> +			skb_reserve(skb, NET_IP_ALIGN);
> +
>  			priv->rx_skbuff[entry] = skb;
>  			priv->rx_skbuff_dma[entry] =
>  			    dma_map_single(priv->device, skb->data, bfsize,
> @@ -1401,7 +1406,7 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
>  	if (priv->plat->enh_desc)
>  		max_mtu = JUMBO_LEN;
>  	else
> -		max_mtu = BUF_SIZE_4KiB;
> +		max_mtu = SKB_MAX_HEAD(NET_SKB_PAD);
>  

minor nit (since NET_IP_ALIGN is 0 anyway on modern x86)
max_mtu = SKB_MAX_HEAD(NET_SKB_PAD + NET_IP_ALIGN);


>  	if ((new_mtu < 46) || (new_mtu > max_mtu)) {
>  		pr_err("%s: invalid MTU, max MTU is: %d\n", dev->name, max_mtu);


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Giuseppe CAVALLARO Oct. 18, 2011, 11:33 a.m. UTC | #2 
On 10/18/2011 12:18 PM, Eric Dumazet wrote:
> Le mardi 18 octobre 2011 à 12:01 +0200, Giuseppe CAVALLARO a écrit :
>> Problem using big mtu around 4096 bytes is you end allocating (4096
>> +NET_SKB_PAD + NET_IP_ALIGN + sizeof(struct skb_shared_info) bytes ->
>> 8192 bytes : order-1 pages
>>
>> It's better to limit the mtu to SKB_MAX_HEAD(NET_SKB_PAD),
>> to have no more than one page per skb.
>>
>> Also the patch changes the netdev_alloc_skb_ip_align() done in
>> init_dma_desc_rings() and uses a variant allowing GFP_KERNEL allocations
>> allowing the driver to load even in case of memory pressure.
>>
>> Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
>> Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
>> ---
>>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   13 +++++++++----
>>  1 files changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index 1848a16..f5ca3be 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -474,11 +474,13 @@ static void init_dma_desc_rings(struct net_device *dev)
>>  	for (i = 0; i < rxsize; i++) {
>>  		struct dma_desc *p = priv->dma_rx + i;
>>  
>> -		skb = netdev_alloc_skb_ip_align(dev, bfsize);
>> +		skb = __netdev_alloc_skb(dev, bfsize + NET_IP_ALIGN,
>> +					 GFP_KERNEL);
>>  		if (unlikely(skb == NULL)) {
>>  			pr_err("%s: Rx init fails; skb is NULL\n", __func__);
>>  			break;
>>  		}
>> +		skb_reserve(skb, NET_IP_ALIGN);
>>  		priv->rx_skbuff[i] = skb;
>>  		priv->rx_skbuff_dma[i] = dma_map_single(priv->device, skb->data,
>>  						bfsize, DMA_FROM_DEVICE);
>> @@ -1176,12 +1178,15 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv)
>>  
>>  			skb = __skb_dequeue(&priv->rx_recycle);
>>  			if (skb == NULL)
>> -				skb = netdev_alloc_skb_ip_align(priv->dev,
>> -								bfsize);
>> +				skb = __netdev_alloc_skb(priv->dev, bfsize +
>> +							 NET_IP_ALIGN,
>> +							 GFP_KERNEL);
>>  
> 
> No, you cant do that in softirq context. We cant sleep here and must use
> GFP_ATOMIC
> Only the init_dma_desc_rings() part is OK, we run in process context and
> are allowed to sleep in memory allocations (GFP_KERNEL)
> 
> 
>>  			if (unlikely(skb == NULL))
>>  				break;
>>  
>> +			skb_reserve(skb, NET_IP_ALIGN);
>> +
>>  			priv->rx_skbuff[entry] = skb;
>>  			priv->rx_skbuff_dma[entry] =
>>  			    dma_map_single(priv->device, skb->data, bfsize,
>> @@ -1401,7 +1406,7 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
>>  	if (priv->plat->enh_desc)
>>  		max_mtu = JUMBO_LEN;
>>  	else
>> -		max_mtu = BUF_SIZE_4KiB;
>> +		max_mtu = SKB_MAX_HEAD(NET_SKB_PAD);
>>  
> 
> minor nit (since NET_IP_ALIGN is 0 anyway on modern x86)
> max_mtu = SKB_MAX_HEAD(NET_SKB_PAD + NET_IP_ALIGN);
> 
> 
>>  	if ((new_mtu < 46) || (new_mtu > max_mtu)) {
>>  		pr_err("%s: invalid MTU, max MTU is: %d\n", dev->name, max_mtu);
> 
> 
> 

Ok! I'm reworking and sending it again.

Thx
Peppe
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diff mbox

Patch

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 1848a16..f5ca3be 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -474,11 +474,13 @@  static void init_dma_desc_rings(struct net_device *dev)
 	for (i = 0; i < rxsize; i++) {
 		struct dma_desc *p = priv->dma_rx + i;
 
-		skb = netdev_alloc_skb_ip_align(dev, bfsize);
+		skb = __netdev_alloc_skb(dev, bfsize + NET_IP_ALIGN,
+					 GFP_KERNEL);
 		if (unlikely(skb == NULL)) {
 			pr_err("%s: Rx init fails; skb is NULL\n", __func__);
 			break;
 		}
+		skb_reserve(skb, NET_IP_ALIGN);
 		priv->rx_skbuff[i] = skb;
 		priv->rx_skbuff_dma[i] = dma_map_single(priv->device, skb->data,
 						bfsize, DMA_FROM_DEVICE);
@@ -1176,12 +1178,15 @@  static inline void stmmac_rx_refill(struct stmmac_priv *priv)
 
 			skb = __skb_dequeue(&priv->rx_recycle);
 			if (skb == NULL)
-				skb = netdev_alloc_skb_ip_align(priv->dev,
-								bfsize);
+				skb = __netdev_alloc_skb(priv->dev, bfsize +
+							 NET_IP_ALIGN,
+							 GFP_KERNEL);
 
 			if (unlikely(skb == NULL))
 				break;
 
+			skb_reserve(skb, NET_IP_ALIGN);
+
 			priv->rx_skbuff[entry] = skb;
 			priv->rx_skbuff_dma[entry] =
 			    dma_map_single(priv->device, skb->data, bfsize,
@@ -1401,7 +1406,7 @@  static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 	if (priv->plat->enh_desc)
 		max_mtu = JUMBO_LEN;
 	else
-		max_mtu = BUF_SIZE_4KiB;
+		max_mtu = SKB_MAX_HEAD(NET_SKB_PAD);
 
 	if ((new_mtu < 46) || (new_mtu > max_mtu)) {
 		pr_err("%s: invalid MTU, max MTU is: %d\n", dev->name, max_mtu);