linux-kernel - Re: 2.6.1[78] page allocation failure. order:3, mode:0x20

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Date:	Sat, 23 Sep 2006 11:50:34 -0700
From:	Auke Kok <auke-jan.h.kok@...el.com>
To:	Andrew Morton <akpm@...l.org>
CC:	David Miller <davem@...emloft.net>, Holger.Kiehl@....de,
	linux-kernel@...r.kernel.org, linux-net@...r.kernel.org,
	netdev@...r.kernel.org, john.ronciak@...el.com
Subject: Re: 2.6.1[78] page allocation failure. order:3, mode:0x20

Andrew Morton wrote:
> On Fri, 22 Sep 2006 22:25:07 -0700 (PDT)
> David Miller <davem@...emloft.net> wrote:
> 
>> From: Andrew Morton <akpm@...l.org>
>> Date: Fri, 22 Sep 2006 21:50:00 -0700
>>
>>> On Fri, 22 Sep 2006 10:10:36 -0700
>>> Auke Kok <auke-jan.h.kok@...el.com> wrote:
>>>
>>>> e1000: account for NET_IP_ALIGN when calculating bufsiz
>>>>
>>>> Account for NET_IP_ALIGN when requesting buffer sizes from netdev_alloc_skb to 
>>>> reduce slab allocation by half.
>>> Could we please do whatever is needed to get this blessed and merged?  This
>>> is such a common problem on such a common driver that I would suggest that
>>> we want this in 2.6.18.x as well.  At least, I'd expect distributors to
>>> ship this fix (they're nuts if they don't) and so it makes sense to deliver
>>> it from kernel.org.
>> The NET_IP_ALIGN existed not just for fun :)  There are ramifications
>> for removing it.
> 
> It's still there, isn't it?
> 
> For the 9k MTU case, for example, we end up allocating 16384 byte skbs
> instead of 32786 kbytes ones.

yes, the only thing I'm doing is accounting for the 2 bytes one steap earlier. 
It works fine for the general case and I tested it too, but I am not too sure 
about the corner cases as the hardware has no notion of mtu at all and could 
possibly overwrite by two bytes. I think my patch actually give the hardware 
two bytes too much now, so we're on the other side (safe) of that problem, but 
I have to verify this first of course.

I'll be wrestling this on monday with Jesse and try to nail it down.

Auke

> 
> 
> diff -puN drivers/net/e1000/e1000_main.c~e1000-account-for-net_ip_align-when-calculating-bufsiz drivers/net/e1000/e1000_main.c
> --- a/drivers/net/e1000/e1000_main.c~e1000-account-for-net_ip_align-when-calculating-bufsiz
> +++ a/drivers/net/e1000/e1000_main.c
> @@ -1101,7 +1101,7 @@ e1000_sw_init(struct e1000_adapter *adap
>  
>  	pci_read_config_word(pdev, PCI_COMMAND, &hw->pci_cmd_word);
>  
> -	adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE;
> +	adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE + NET_IP_ALIGN;
>  	adapter->rx_ps_bsize0 = E1000_RXBUFFER_128;
>  	hw->max_frame_size = netdev->mtu +
>  			     ENET_HEADER_SIZE + ETHERNET_FCS_SIZE;
> @@ -3163,26 +3163,27 @@ e1000_change_mtu(struct net_device *netd
>  	 * larger slab size
>  	 * i.e. RXBUFFER_2048 --> size-4096 slab */
>  
> -	if (max_frame <= E1000_RXBUFFER_256)
> +	if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_256)
>  		adapter->rx_buffer_len = E1000_RXBUFFER_256;
> -	else if (max_frame <= E1000_RXBUFFER_512)
> +	else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_512)
>  		adapter->rx_buffer_len = E1000_RXBUFFER_512;
> -	else if (max_frame <= E1000_RXBUFFER_1024)
> +	else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_1024)
>  		adapter->rx_buffer_len = E1000_RXBUFFER_1024;
> -	else if (max_frame <= E1000_RXBUFFER_2048)
> +	else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_2048)
>  		adapter->rx_buffer_len = E1000_RXBUFFER_2048;
> -	else if (max_frame <= E1000_RXBUFFER_4096)
> +	else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_4096)
>  		adapter->rx_buffer_len = E1000_RXBUFFER_4096;
> -	else if (max_frame <= E1000_RXBUFFER_8192)
> +	else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_8192)
>  		adapter->rx_buffer_len = E1000_RXBUFFER_8192;
> -	else if (max_frame <= E1000_RXBUFFER_16384)
> +	else
>  		adapter->rx_buffer_len = E1000_RXBUFFER_16384;
>  
>  	/* adjust allocation if LPE protects us, and we aren't using SBP */
>  	if (!adapter->hw.tbi_compatibility_on &&
>  	    ((max_frame == MAXIMUM_ETHERNET_FRAME_SIZE) ||
>  	     (max_frame == MAXIMUM_ETHERNET_VLAN_SIZE)))
> -		adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE;
> +		adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE +
> +					NET_IP_ALIGN;
>  
>  	netdev->mtu = new_mtu;
>  
> @@ -4002,7 +4003,8 @@ e1000_alloc_rx_buffers(struct e1000_adap
>  	struct e1000_buffer *buffer_info;
>  	struct sk_buff *skb;
>  	unsigned int i;
> -	unsigned int bufsz = adapter->rx_buffer_len + NET_IP_ALIGN;
> +	/* we have already accounted for NET_IP_ALIGN */
> +	unsigned int bufsz = adapter->rx_buffer_len;
>  
>  	i = rx_ring->next_to_use;
>  	buffer_info = &rx_ring->buffer_info[i];
> _
-
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