On 6.05.2022 09:44, Rafał Miłecki wrote:
On 5.05.2022 18:04, Andrew Lunn wrote:
you'll see that most used functions are:
v7_dma_inv_range
__irqentry_text_end
l2c210_inv_range
v7_dma_clean_range
bcma_host_soc_read32
__netif_receive_skb_core
arch_cpu_idle
l2c210_clean_range
fib_table_lookup
There is a lot of cache management functions here. Might sound odd,
but have you tried disabling SMP? These cache functions need to
operate across all CPUs, and the communication between CPUs can slow
them down. If there is only one CPU, these cache functions get simpler
and faster.
It just depends on your workload. If you have 1 CPU loaded to 100% and
the other 3 idle, you might see an improvement. If you actually need
more than one CPU, it will probably be worse.
It seems to lower my NAT speed from ~362 Mb/s to 320 Mb/s but it feels
more stable now (lower variations). Let me spend some time on more
testing.
For a context I test various kernel commits / configs using:
iperf -t 120 -i 10 -c 192.168.13.1
I did more testing with # CONFIG_SMP is not set
Good thing:
During a single iperf session I get noticably more stable speed.
With SMP: x ± 2,86%
Without SMP: x ± 0,96%
Bad thing:
Across kernel commits / config changes speed still varies.
So disabling CONFIG_SMP won't help me looking for kernel regressions.
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