8a8633978b
This patch makes use of build_skb() throughout in driver's receieve data path [HW gro flow and non HW gro flow]. With this, driver can build skb directly from the page segments which are already mapped to the hardware instead of allocating new SKB via netdev_alloc_skb() and memcpy the data which is quite costly. This really improves performance (keeping same or slight gain in rx throughput) in terms of CPU utilization which is significantly reduced [almost half] in non HW gro flow where for every incoming MTU sized packet driver had to allocate skb, memcpy headers etc. Additionally in that flow, it also gets rid of bunch of additional overheads [eth_get_headlen() etc.] to split headers and data in the skb. Tested with: system: 2 sockets, 4 cores per socket, hyperthreading, 2x4x2=16 cores iperf [server]: iperf -s iperf [client]: iperf -c <server_ip> -t 500 -i 10 -P 32 HW GRO off – w/o build_skb(), throughput: 36.8 Gbits/sec Average: CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle Average: all 0.59 0.00 32.93 0.00 0.00 43.07 0.00 0.00 23.42 HW GRO off - with build_skb(), throughput: 36.9 Gbits/sec Average: CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle Average: all 0.70 0.00 31.70 0.00 0.00 25.68 0.00 0.00 41.92 HW GRO on - w/o build_skb(), throughput: 36.9 Gbits/sec Average: CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle Average: all 0.86 0.00 24.14 0.00 0.00 6.59 0.00 0.00 68.41 HW GRO on - with build_skb(), throughput: 37.5 Gbits/sec Average: CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle Average: all 0.87 0.00 23.75 0.00 0.00 6.19 0.00 0.00 69.19 Signed-off-by: Ariel Elior <ariel.elior@cavium.com> Signed-off-by: Manish Chopra <manish.chopra@cavium.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.