>On Wed, Nov 11, 2015 at 03:06:02PM +0000, Mark Kavanagh wrote:
>> Add support for Jumbo Frames to DPDK-enabled port types,
>> using single-segment-mbufs.
>>
>> Using this approach, the amount of memory allocated for each mbuf
>> to store frame data is increased to a value greater than 1518B
>> (typical Ethernet maximum frame length). The increased space
>> available in the mbuf means that an entire Jumbo Frame can be carried
>> in a single mbuf, as opposed to partitioning it across multiple mbuf
>> segments.
>>
>> The amount of space allocated to each mbuf to hold frame data is
>> defined by the user at compile time; if this frame length is not a
>> multiple of the DPDK NIC driver's minimum Rx buffer length, the frame
>> length is rounded up to the closest value that is.
>>
>> Signed-off-by: Mark Kavanagh <mark.b.kavan...@intel.com>
>> ---
>> INSTALL.DPDK.md | 67 ++++++++++++++++++++-
>> lib/netdev-dpdk.c | 176
>> ++++++++++++++++++++++++++++++++++++++++++-----------
>> 2 files changed, 207 insertions(+), 36 deletions(-)
>>
>> diff --git a/INSTALL.DPDK.md b/INSTALL.DPDK.md
>> index 96b686c..9a30f88 100644
>> --- a/INSTALL.DPDK.md
>> +++ b/INSTALL.DPDK.md
>> @@ -859,10 +859,70 @@ by adding the following string:
>> to <interface> sections of all network devices used by DPDK. Parameter 'N'
>> determines how many queues can be used by the guest.
>>
>> +
>> +Jumbo Frames
>> +------------
>> +
>> +Support for Jumbo Frames may be enabled at compile-time for DPDK-type ports.
>
>It seems this could be dynamic and proportional to the MTU being used
>by the port and not a compile-time option which depends on the NIC
>hardware specs. Perhaps I am missing something.
>
Hi Flavio - thanks for your feedback.
Just to clarify, when you say 'dynamic', I presume that you mean that the MTU
can be specified at runtime. Bearing this in mind, is the behavior that you
have in mind that:
- the MTU for each DPDK port should be specified when the port is added
to a bridge?
- and the granularity at which MTUs are assigned to DPDK-type ports
should be on a per-port basis, rather than the (admittedly) coarse-grained
'one-for-all' approach implemented here?
It's worth noting that due to the fact that DPDK ports are outside the reach of
the Linux kernel, their MTU can't be changed using standard tools, such as
'ifconfig', 'ip link', etc. Furthermore, the OVS 'Interface' table's 'MTU'
attribute cannot currently be set programmatically, outside of the
aforementioned tools. In this way, the MTU of DPDK ports is always limited in
how dynamic it can be, hence, once set, the MTU for a DPDK port is (currently)
immutable.
I'm not quite sure if I follow the second part of your comment regarding
proportionality to the port's MTU - could you elaborate a bit more on this?
Thanks in advance,
Mark
>Thanks,
>fbl
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