netdev - Re: [PATCH net-next RFC 2/4] virtio-net: transmit napi

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Message-Id: <20170306.105522.1168429366842291288.davem@davemloft.net>
Date:   Mon, 06 Mar 2017 10:55:22 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     willemdebruijn.kernel@...il.com
Cc:     jasowang@...hat.com, netdev@...r.kernel.org, mst@...hat.com,
        willemb@...gle.com
Subject: Re: [PATCH net-next RFC 2/4] virtio-net: transmit napi

From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Date: Mon, 6 Mar 2017 12:50:19 -0500

>>>   drivers/net/virtio_net.c | 73
>>> ++++++++++++++++++++++++++++++++++++++++--------
>>>   1 file changed, 61 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>> index 8c21e9a4adc7..9a9031640179 100644
>>> --- a/drivers/net/virtio_net.c
>>> +++ b/drivers/net/virtio_net.c
>>> @@ -33,6 +33,8 @@
>>>   static int napi_weight = NAPI_POLL_WEIGHT;
>>>   module_param(napi_weight, int, 0444);
>>>   +static int napi_tx_weight = NAPI_POLL_WEIGHT;
>>> +
>>
>>
>> Maybe we should use module_param for this? Or in the future, use
>> tx-frames-irq for a per-device configuration.
> 
> This option should eventually just go away, and napi tx become the
> standard mode.
> 
> In the short term, while we evaluate it on varied workloads, a
> module_param sounds good to me. In general that is frowned
> upon, as it leads to different configuration interfaces for each
> device driver. But that should not be a concern in this limited
> case.

In any event, do we really need a TX weight at all?

I guess you tried this, but why doesn't it not work to just do
all TX work unconditionally in a NAPI poll pass?  This is how
we encourage all NIC drivers to handle this.