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hv_netvsc: Update netvsc Document for UDP hash level setting

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Update Documentation/networking/netvsc.txt for UDP hash level setting
and related info.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Haiyang Zhang 2017-08-21 19:22:40 -07:00 committed by David S. Miller
parent 4823eb2f3a
commit 3b0c34580b
1 changed files with 17 additions and 5 deletions
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22
Documentation/networking/netvsc.txt
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@ -21,11 +21,23 @@ Features
--------------------
Hyper-V supports receive side scaling. For TCP, packets are
distributed among available queues based on IP address and port
number. Current versions of Hyper-V host, only distribute UDP
packets based on the IP source and destination address.
The port number is not used as part of the hash value for UDP.
Fragmented IP packets are not distributed between queues;
all fragmented packets arrive on the first channel.
number.
For UDP, we can switch UDP hash level between L3 and L4 by ethtool
command. UDP over IPv4 and v6 can be set differently. The default
hash level is L4. We currently only allow switching TX hash level
from within the guests.
On Azure, fragmented UDP packets have high loss rate with L4
hashing. Using L3 hashing is recommended in this case.
For example, for UDP over IPv4 on eth0:
To include UDP port numbers in hasing:
ethtool -N eth0 rx-flow-hash udp4 sdfn
To exclude UDP port numbers in hasing:
ethtool -N eth0 rx-flow-hash udp4 sd
To show UDP hash level:
ethtool -n eth0 rx-flow-hash udp4
Generic Receive Offload, aka GRO
--------------------------------