A performance hit of approximately 34% in receive numbers for some packet sizes
is
seen when testing traffic over ixgbe links using the network test netperf.
Starting with the top of tree commit 7addb3e4ad3db6a95a953c59884921b5883dcdec,
a git bisect narrowed the issue down to:
commit 6f429223b31c550b835b4f066ac034d0cf0cc71e
ixgbe: Add support for build_skb
This patch adds build_skb support to the Rx path. There are several
advantages to this change.
1. It avoids the memcpy and skb->head allocation for small packets which
improves performance by about 5% in my tests.
2. It avoids the memcpy, skb->head allocation, and eth_get_headlen
for larger packets improving performance by about 10% in my tests.
3. For VXLAN packets it allows the full header to be in skb->data which
improves the performance by as much as 30% in some of my tests.
Netperf was sourced from:
https://hewlettpackard.github.io/netperf/
Two machines were directly connected via ixgbe links.
The process "netserver" was started on 10.196.11.8, and running this test:
# netperf -l 60 -H 10.196.11.8 -i 10,2 -I 99,10 -t UDP_STREAM -- -m 64 -s 32768
-S 32768
showed that on machines without the patch, we typically see performance
like:
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
65536 64 60.00 35435847 0 302.38 <-- SEND
65536 60.00 35391087 302.00 <-- RECEIVE
or
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
65536 64 60.00 33708816 0 287.65
65536 60.00 33706010 287.62
However, on machines with the patch, receive performance is seen to fall by an
average of 34%, e.g.:
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
65536 64 60.00 35179881 0 300.20
65536 60.00 21418471 182.77
or
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
65536 64 60.00 36937716 0 315.20
65536 60.00 16838656 143.69
William Kucharski
william.kuchar...@oracle.com
