Re: [PATCH net] net: mana: Fix perf regression: remove rx_cqes, tx_cqes counters

From: Jiri Pirko
Date: Fri May 26 2023 - 06:44:15 EST

Wed, May 24, 2023 at 11:22:00PM CEST, haiyangz@xxxxxxxxxxxxx wrote:
>The apc->eth_stats.rx_cqes is one per NIC (vport), and it's on the
>frequent and parallel code path of all queues. So, r/w into this
>single shared variable by many threads on different CPUs creates a
>lot caching and memory overhead, hence perf regression. And, it's
>not accurate due to the high volume concurrent r/w.
>Since the error path of mana_poll_rx_cq() already has warnings, so
>keeping the counter and convert it to a per-queue variable is not
>necessary. So, just remove this counter from this high frequency
>code path.
>Also, remove the tx_cqes counter for the same reason. We have
>warnings & other counters for errors on that path, and don't need
>to count every normal cqe processing.
>Cc: stable@xxxxxxxxxxxxxxx
>Fixes: bd7fc6e1957c ("net: mana: Add new MANA VF performance counters for easier troubleshooting")
>Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>

Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>