Re: [PATCH net-next 1/1] qede: Add build_skb() support.

[David Miller <davem@davemloft.net>]

From: Manish Chopra <manish.chopra@cavium.com>
Date: Thu, 17 May 2018 12:05:00 -0700

> 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>

Looks great, applied, thank you.