lan743x: fix rx_napi_poll/interrupt ping-pong
Even if there is more rx data waiting on the chip, the rx napi poll fn will never run more than once - it will always read a few buffers, then bail out and re-arm interrupts. Which results in ping-pong between napi and interrupt. This defeats the purpose of napi, and is bad for performance. Fix by making the rx napi poll behave identically to other ethernet drivers: 1. initialize rx napi polling with an arbitrary budget (64). 2. in the polling fn, return full weight if rx queue is not depleted, this tells the napi core to "keep polling". 3. update the rx tail ("ring the doorbell") once for every 8 processed rx ring buffers. Thanks to Jakub Kicinski, Eric Dumazet and Andrew Lunn for their expert opinions and suggestions. Tested with 20 seconds of full bandwidth receive (iperf3): rx irqs softirqs(NET_RX) ----------------------------- before 23827 33620 after 129 4081 Tested-by: Sven Van Asbroeck <thesven73@gmail.com> # lan7430 Fixes: 23f0703c ("lan743x: Add main source files for new lan743x driver") Signed-off-by:Sven Van Asbroeck <thesven73@gmail.com> Link: https://lore.kernel.org/r/20201215161954.5950-1-TheSven73@gmail.com Signed-off-by:
Jakub Kicinski <kuba@kernel.org>
parent
3db1a3fa
Please register or sign in to comment