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4d86d38186
Add support for RX checksum offload. This is enabled by default and
may be disabled and re-enabled using ethtool:
# ethtool -K eth0 rx off
# ethtool -K eth0 rx on
The RAVB provides a simple checksumming scheme which appears to be
completely compatible with CHECKSUM_COMPLETE: sum of all packet data after
the L2 header is appended to packet data; this may be trivially read by the
driver and used to update the skb accordingly.
In terms of performance throughput is close to gigabit line-rate both with
and without RX checksum offload enabled. Perf output, however, appears to
indicate that significantly less time is spent in do_csum(). This is as
expected.
Test results with RX checksum offload enabled:
# /usr/bin/perf_3.16 record -o /run/perf.data -a netperf -t TCP_MAERTS -H 10.4.3.162
MIGRATED TCP MAERTS TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.4.3.162 () port 0 AF_INET : demo
enable_enobufs failed: getprotobyname
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
87380 16384 16384 10.00 937.54
Summary of output of perf report:
18.28% ksoftirqd/0 [kernel.kallsyms] [k] _raw_spin_unlock_irqrestore
10.34% ksoftirqd/0 [kernel.kallsyms] [k] __pi_memcpy
9.83% ksoftirqd/0 [kernel.kallsyms] [k] ravb_poll
7.89% ksoftirqd/0 [kernel.kallsyms] [k] skb_put
4.01% ksoftirqd/0 [kernel.kallsyms] [k] dev_gro_receive
3.37% netperf [kernel.kallsyms] [k] __arch_copy_to_user
3.17% swapper [kernel.kallsyms] [k] arch_cpu_idle
2.55% swapper [kernel.kallsyms] [k] tick_nohz_idle_enter
2.04% ksoftirqd/0 [kernel.kallsyms] [k] __pi___inval_dcache_area
2.03% swapper [kernel.kallsyms] [k] _raw_spin_unlock_irq
1.96% ksoftirqd/0 [kernel.kallsyms] [k] __netdev_alloc_skb
1.59% ksoftirqd/0 [kernel.kallsyms] [k] __slab_alloc.isra.83
Test results without RX checksum offload enabled:
# /usr/bin/perf_3.16 record -o /run/perf.data -a netperf -t TCP_MAERTS -H 10.4.3.162
MIGRATED TCP MAERTS TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.4.3.162 () port 0 AF_INET : demo
enable_enobufs failed: getprotobyname
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec
87380 16384 16384 10.00 940.20
Summary of output of perf report:
17.10% ksoftirqd/0 [kernel.kallsyms] [k] _raw_spin_unlock_irqrestore
10.99% ksoftirqd/0 [kernel.kallsyms] [k] __pi_memcpy
8.87% ksoftirqd/0 [kernel.kallsyms] [k] ravb_poll
8.16% ksoftirqd/0 [kernel.kallsyms] [k] skb_put
7.42% ksoftirqd/0 [kernel.kallsyms] [k] do_csum
3.91% ksoftirqd/0 [kernel.kallsyms] [k] dev_gro_receive
2.31% swapper [kernel.kallsyms] [k] arch_cpu_idle
2.16% ksoftirqd/0 [kernel.kallsyms] [k] __pi___inval_dcache_area
2.14% ksoftirqd/0 [kernel.kallsyms] [k] __netdev_alloc_skb
1.93% netperf [kernel.kallsyms] [k] __arch_copy_to_user
1.79% swapper [kernel.kallsyms] [k] tick_nohz_idle_enter
1.63% ksoftirqd/0 [kernel.kallsyms] [k] __slab_alloc.isra.83
Above results collected on an R-Car Gen 3 Salvator-X/r8a7796 ES1.0.
Also tested on a R-Car Gen 3 Salvator-X/r8a7795 ES1.0.
By inspection this also appears to be compatible with the ravb found
on R-Car Gen 2 SoCs, however, this patch is currently untested on such
hardware.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.