netdev - Re: [PATCH net-next 1/5] net: tso: double TSO_HEADER

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Date:   Wed, 17 Jun 2020 17:14:06 -0700
From:   Eric Dumazet <erdnetdev@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Antoine Tenart <antoine.tenart@...tlin.com>
Subject: Re: [PATCH net-next 1/5] net: tso: double TSO_HEADER_SIZE value



On 6/17/20 5:02 PM, Jakub Kicinski wrote:
> On Wed, 17 Jun 2020 11:48:15 -0700 Eric Dumazet wrote:
>> Transport header size could be 60 bytes, and network header
>> size can also be 60 bytes. Add the Ethernet header and we
>> are above 128 bytes.
>>
>> Since drivers using net/core/tso.c usually allocates
>> one DMA coherent piece of memory per TX queue, this patch
>> might cause issues if a driver was using too many slots.
>>
>> For 1024 slots, we would need 256 KB of physically
>> contiguous memory instead of 128 KB.
>>
>> Alternative fix would be to add checks in the fast path,
>> but this involves more work in all drivers using net/core/tso.c.
>>
>> Fixes: f9cbe9a556af ("net: define the TSO header size in net/tso.h")
>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>> Cc: Antoine Tenart <antoine.tenart@...tlin.com>
> 
> Some warnings popping up in this series with W=1 C=1:
> 
> drivers/net/ethernet/marvell/octeontx2/af/common.h:65:26: warning: cast truncates bits from constant value (100 becomes 0)
>

Nice, thanks I will take a look.