On 02/24/2014 11:17 AM, David Laight wrote:
From: Daniel Borkmann
Drivers are allowed to set NETIF_F_SCTP_CSUM if they have
hardware crc32c checksumming support for the SCTP protocol.
Currently, NETIF_F_SCTP_CSUM flag is available in igb,
ixgbe, i40e/i40evf drivers and for vlan devices.
If we don't have NETIF_F_SCTP_CSUM then crc32c is done
through CPU instructions, invoked from crypto layer, or
if not available as slow-path fallback in software.
Currently, loopback device propagates checksum offloading
feature flags in dev->features, but is missing SCTP checksum
offloading. Therefore, account for NETIF_F_SCTP_CSUM as
well.
Before patch:
./netperf_sctp -H 192.168.0.100 -t SCTP_STREAM_MANY
SCTP 1-TO-MANY STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.0.100 () port 0 AF_INET
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
4194304 4194304 4096 10.00 4683.50
After patch:
...
4194304 4194304 4096 10.00 15348.26
That seems a much larger increase than you'd expect from removing
a software CRC of the data chunks.
Are you sure that some other difference in the data flows wasn't
also triggered.
Yes, I run this multiple times with similar results and I double-checked
it with perf. Current code triggers crc32c implementation in software
fallback on my machine which is very expensive.
I'm also not sure that 4096 is a representative message size for SCTP.
I used netperf default in this case.
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