From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Network Development <netdev@vger.kernel.org>,
Jason Wang <jasowang@redhat.com>,
virtualization@lists.linux-foundation.org,
David Miller <davem@davemloft.net>,
Willem de Bruijn <willemb@google.com>
Subject: Re: [PATCH net-next 2/3] virtio-net: transmit napi
Date: Mon, 3 Apr 2017 01:07:49 -0400 [thread overview]
Message-ID: <CAF=yD-+5+X6UBYaX=Dh3M3caty0fJ7cjamTfX0=_+Lwx6r_VQw@mail.gmail.com> (raw)
In-Reply-To: <20170403052938-mutt-send-email-mst@kernel.org>
On Sun, Apr 2, 2017 at 10:30 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Sun, Apr 02, 2017 at 04:10:11PM -0400, Willem de Bruijn wrote:
>> From: Willem de Bruijn <willemb@google.com>
>>
>> Convert virtio-net to a standard napi tx completion path. This enables
>> better TCP pacing using TCP small queues and increases single stream
>> throughput.
>>
>> The virtio-net driver currently cleans tx descriptors on transmission
>> of new packets in ndo_start_xmit. Latency depends on new traffic, so
>> is unbounded. To avoid deadlock when a socket reaches its snd limit,
>> packets are orphaned on tranmission. This breaks socket backpressure,
>> including TSQ.
>>
>> Napi increases the number of interrupts generated compared to the
>> current model, which keeps interrupts disabled as long as the ring
>> has enough free descriptors. Keep tx napi optional for now. Follow-on
>> patches will reduce the interrupt cost.
>>
>> Signed-off-by: Willem de Bruijn <willemb@google.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>> drivers/net/virtio_net.c | 63 ++++++++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 53 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 6aac0ad0d9b2..95d938e82080 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -33,9 +33,10 @@
>> static int napi_weight = NAPI_POLL_WEIGHT;
>> module_param(napi_weight, int, 0444);
>>
>> -static bool csum = true, gso = true;
>> +static bool csum = true, gso = true, napi_tx = true;
>> module_param(csum, bool, 0444);
>> module_param(gso, bool, 0444);
>> +module_param(napi_tx, bool, 0644);
>>
>> /* FIXME: MTU in config. */
>> #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
>
> Off by default seems safer until we can find better ways
> to reduce the overhead, esp for UDP.
Okay, I'll change that. I don't have an immediate idea for that
unidirectional case.
next prev parent reply other threads:[~2017-04-03 5:08 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-02 20:10 [PATCH net-next 0/3] virtio-net tx napi Willem de Bruijn
2017-04-02 20:10 ` [PATCH net-next 1/3] virtio-net: napi helper functions Willem de Bruijn
2017-04-02 20:10 ` Willem de Bruijn
2017-04-02 20:10 ` [PATCH net-next 2/3] virtio-net: transmit napi Willem de Bruijn
2017-04-02 20:10 ` Willem de Bruijn
2017-04-03 2:30 ` Michael S. Tsirkin
2017-04-03 5:07 ` Willem de Bruijn
2017-04-03 5:07 ` Willem de Bruijn [this message]
2017-04-02 20:10 ` [PATCH net-next 3/3] virtio-net: clean tx descriptors from rx napi Willem de Bruijn
2017-04-02 20:10 ` Willem de Bruijn
2017-04-03 2:47 ` Michael S. Tsirkin
2017-04-03 5:02 ` Willem de Bruijn
2017-04-03 5:02 ` Willem de Bruijn
2017-04-07 19:28 ` Michael S. Tsirkin
2017-04-07 19:28 ` Michael S. Tsirkin
2017-04-07 20:59 ` Willem de Bruijn
2017-04-07 20:59 ` Willem de Bruijn
2017-04-07 21:10 ` Michael S. Tsirkin
2017-04-07 21:10 ` Michael S. Tsirkin
2017-04-07 21:14 ` Willem de Bruijn
2017-04-07 21:14 ` Willem de Bruijn
2017-04-03 2:47 ` Michael S. Tsirkin
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