netdev - Re: [PATCH] bgmac: Remove all offloading features, including GRO.

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Date:   Wed, 20 Sep 2017 14:32:40 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     rosenp@...il.com, Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH] bgmac: Remove all offloading features, including GRO.

On 09/20/2017 02:27 PM, rosenp@...il.com wrote:
> Sorry for the noise. After more testing I've found out that the cause
> was that I had BBR enabled on my laptop. Switching back to CUBIC fixed
> the issue.
> 
> In other words, this patch is detrimental.

Quite unsurprisingly, thanks for coming back, and please don't top-post
on netdev.

> 
> ~67mbps - gro off
> ~87mbps - gro on
> 
> On Fri, 2017-09-15 at 23:04 -0700, Florian Fainelli wrote:
>> On September 15, 2017 5:38:42 PM PDT, rosenp@...il.com wrote:
>>> I have not. Unfortunately I own no gigabit hardware to test this
>>> on.
>>> The MIPS CPU runs at 300MHz on my unit.
>>>
>>
>> bgmac is used on Gigabit capable hardware, like Northstar and
>> Northstar Plus, and others too, so unless you can get access to such
>> HW or get confirmation from someone that your patches changes
>> something, I would just drop this change and not bother. This is
>> already not 100mbits/sec linerate...
>>
>>> On Fri, 2017-09-15 at 17:34 -0700, Eric Dumazet wrote:
>>>> On Fri, 2017-09-15 at 17:23 -0700, Rosen Penev wrote:
>>>>> On a linksys E1200v1 (actually a crossflashed E1000v2), the
>>>>> offloading features give no measurable benefit to speed or
>>>>> latency.
>>>>> Furthermore, disabling GRO actually improves iperf performance
>>>>> by a
>>>>> whoppimg 3mbps. Results:
>>>>>
>>>>> Currently:
>>>>>
>>>>> v2: Changed napi_gro_receive to netif_receive_skb. Seems to
>>>>> have an
>>>>> identical result.
>>>>>
>>>>> Signed-off-by: Rosen Penev <rosenp@...il.com>
>>>>> ---
>>>>>  drivers/net/ethernet/broadcom/bgmac.c | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/net/ethernet/broadcom/bgmac.c
>>>>> b/drivers/net/ethernet/broadcom/bgmac.c
>>>>> index 48d672b204a4..1fb0053aeee7 100644
>>>>> --- a/drivers/net/ethernet/broadcom/bgmac.c
>>>>> +++ b/drivers/net/ethernet/broadcom/bgmac.c
>>>>> @@ -483,7 +483,7 @@ static int bgmac_dma_rx_read(struct bgmac
>>>>> *bgmac, struct bgmac_dma_ring *ring,
>>>>>  			skb->protocol = eth_type_trans(skb,
>>>>> bgmac-
>>>>>> net_dev);
>>>>>
>>>>>  			bgmac->net_dev->stats.rx_bytes += len;
>>>>>  			bgmac->net_dev->stats.rx_packets++;
>>>>> -			napi_gro_receive(&bgmac->napi, skb);
>>>>> +			netif_receive_skb(skb);
>>>>>  			handled++;
>>>>>  		} while (0);
>>>>>  
>>>>
>>>> And have you tested 1Gbit link speed ?
>>>> ( Or 2.5 Gbit link speed )
>>>>
>>>> If you want to disable GRO on your host, fine : you can use
>>>> ethtool
>>>> -K
>>>>
>>>>
>>>>
>>
>> (please don't top-post)


-- 
Florian