On 8/10/2018 3:20 PM, Toke Høiland-Jørgensen wrote:

Arend van Spriel [off-list ref] writes:

quoted

On 8/8/2018 9:00 PM, Peter Oh wrote:

quoted

On 08/08/2018 03:40 AM, Wen Gong wrote:

quoted

Add a field for ath10k to adjust the sk_pacing_shift, mac80211 set
the default value to 8, and ath10k will change it to 6. Then mac80211
will use the changed value 6 as sk_pacing_shift since 6 is the best
value for tx throughput by test result.

I don't think you can convince people with the numbers unless you
provide latency along with the numbers and also measurement result on
different chipsets as Michal addressed (QCA4019, QCA9984, etc.) From
users view point, I also agree on Toke that we cannot scarify latency
for the small throughput improvement.

Yeah. The wireless industry (admittedly that is me too :-p ) has been
focused on just throughput long enough.

Tell me about it ;)

quoted

All the preaching about bufferbloat from Dave and others is (just)
starting to sink in here and there.

Yeah, I've noticed; this is good!

quoted

Now as for the value of the sk_pacing_shift I think we agree it
depends on the specific device so in that sense the api makes sense,
but I think there are a lot of variables so I was wondering if we
could introduce a sysctl parameter for it. Does that make sense?

I'm not sure a sysctl parameter would make sense; for one thing, it
would be global for the host, while different network interfaces will
probably need different values. And for another, I don't think it's
something a user can reasonably be expected to set correctly, and I
think it *is* actually possible to pick a value that works well at the
driver level.

I not sure either. Do you think a user could come up with something like 
this (found here [1]):

sysctl -w net.core.rmem_max=8388608
sysctl -w net.core.wmem_max=8388608
sysctl -w net.core.rmem_default=65536
sysctl -w net.core.wmem_default=65536
sysctl -w net.ipv4.tcp_rmem='4096 87380 8388608'
sysctl -w net.ipv4.tcp_wmem='4096 65536 8388608'
sysctl -w net.ipv4.tcp_mem='8388608 8388608 8388608'
sysctl -w net.ipv4.route.flush=1

Now the page listing this config claims this is for use "on Linux 2.4+ 
for high-bandwidth applications". Beats me if it still is correct in 4.17.

Anyway, sysctl is nice for parameterizing code that is built-in the 
kernel so you don't need to rebuild it. mac80211 tends to be a module in 
most distros so maybe sysctl is not a good fit. So lets agree on that.

Picking a value at driver level may be possible, but a driver tends to 
support a number of different devices. So how do you see the picking 
work. Some static table with entries for the different devices?

Regards,
Arend

[1] https://wwwx.cs.unc.edu/~sparkst/howto/network_tuning.php