netdev - Re: igb mtu change

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Date:	Thu, 18 Oct 2012 05:40:32 +0530
From:	ratheesh kannoth <ratheesh.ksz@...il.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	e1000-devel@...ts.sourceforge.net, linux-net@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: igb mtu change

On Thu, Oct 18, 2012 at 1:39 AM, Alexander Duyck
<alexander.h.duyck@...el.com> wrote:
> The current igb driver does receive the frame data into 2K buffers, and
> transmits up to MTU size.  The only limitation on the size of the frame
> you can transmit is the netdev->mtu which the driver doesn't evaluate.
> It is evaluated at the network stack level.  The igb driver can send up
> to 9K frames, in addition it can TSO up to 64K frames and send them in
> 9K chunks so I am not sure what you are asking.
>
> Thanks,
>
> Alex

Thanks a lot.
I am using igb-3.3.6  for hardware   - vendor=0x8086, device=0x10e6
only CONFIG_IGB_DISABLE_PACKET_SPLIT defined.


I will explain my question in detail.


int  i = 0 ;
rx_desc = IGB_RX_DESC(rx_ring, i);

if(!(igb_test_staterr(rx_desc, E1000_RXD_STAT_EOP) ) {
     printk ( "part of Jumbo frame ...Not the last junk ");
}


If mtu is 1500,  and jumbo frame size is 9200.   I get the printk  -
part of Jumbo frame ...Not the last junk .

But if i change mtu to 9216,  the condition ,
!(igb_test_staterr(rx_desc, E1000_RXD_STAT_EOP) , looks like
never satisfied .

Thanks,
Ratheesh
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