From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: souvikdey33 <sodey@sonusnet.com>,
stephen@networkplumber.org, huawei.xie@intel.com, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2] add mtu set in virtio
Date: Wed, 7 Sep 2016 11:16:47 +0200 [thread overview]
Message-ID: <d141aa3a-e024-19ac-fe99-a9ea07002ce4@redhat.com> (raw)
In-Reply-To: <20160907032547.GG23158@yliu-dev.sh.intel.com>
On 09/07/2016 05:25 AM, Yuanhan Liu wrote:
> On Tue, Aug 30, 2016 at 09:57:39AM +0200, Maxime Coquelin wrote:
>> Hi Souvik,
>>
>> On 08/30/2016 01:02 AM, souvikdey33 wrote:
>>> Signed-off-by: Souvik Dey <sodey@sonusnet.com>
>>>
>>> Fixes: 1fb8e8896ca8 ("Signed-off-by: Souvik Dey <sodey@sonusnet.com>")
>>> Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
>>>
>>> Virtio interfaces should also support setting of mtu, as in case of cloud
>>> it is expected to have the consistent mtu across the infrastructure that
>>> the dhcp server sends and not hardcoded to 1500(default).
>>> ---
>>> drivers/net/virtio/virtio_ethdev.c | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>
>> FYI, there are some on-going changes in the VIRTIO specification
>> so that the VHOST interface exposes its MTU to its VIRTIO peer.
>> It may also be used as an alternative of what you patch achieves.
>>
>> I am working on its implementation in Qemu/DPDK, our goal being to
>> reduce performance drops for small packets with Rx mergeable buffers
>> feature enabled.
>
> Mind to educate me a bit on how that works?
Of course.
Basically, this is a way to advise the MTU we want in the guest.
In the guest, if GRO is not enabled:
- In case of Kernel virtio-net, it could be used to
size the SKBs at the expected MTU. If possible, we could disable Rx
mergeable buffers.
- In case of virtio PMD, if the MTU advised by host is lower than the
pre-allocated mbuf size for the receive queue, then we should not need
mergeable buffers.
Does that sound reasonnable?
Do I miss something?
Thanks,
Maxime
next prev parent reply other threads:[~2016-09-07 9:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-29 23:02 souvikdey33
2016-08-30 7:57 ` Maxime Coquelin
2016-09-01 22:20 ` Dey, Souvik
2016-09-02 7:05 ` Maxime Coquelin
2016-09-07 2:11 ` Dey, Souvik
2016-09-07 8:28 ` Maxime Coquelin
2016-09-07 3:25 ` Yuanhan Liu
2016-09-07 9:16 ` Maxime Coquelin [this message]
2016-09-08 7:30 ` Yuanhan Liu
2016-09-08 7:50 ` Maxime Coquelin
2016-09-08 7:57 ` Yuanhan Liu
2016-09-09 3:44 ` Dey, Souvik
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