Ethernet Ping - Coalesce help

Hi.
I have a 7i76e. Typical Ping times are 0.250ms.
Intel ethernet, so it should benefit from the coalesce mod.
File in use is /etc/network/interfaces

Attached screenshots illustrate the results of dmesg, ip, ping times and the interfaces text.

In other posts I've noticed that sometimes the "-" character is not an ANCII character. In this case I have manually typed in the last string using the "minus" key on the keyboard. I think I need a fresh pair of eyes. What am I doing wrong??
Thanks.
 
 
 
 


 

Whats wrong?
Looks OK to me. DId you restart your network or reboot?

What exactly is the problem?

try "sudo taskset -c 3 chrt 99 ping -i .001 -q 10.10.10.10", that assumes you are running with "isolcpus=3"

Sorry,  yes, whatever i do the ethernet latency doesn't get better from 250ms, including trying the above. I was under the impression that 250ms was on the long side and should/could be better??

250µs -- 250ms would be completely unuseable. AFAIK ping time of 250µs should work with no problems.

If you want a fresh pair of eyes you need to give them something to look at -- what kind of hardware is this, how much ram, kernel version, kernel command line, etc...

1. Did you verify the you actually disabled IRQ coalescing?
(a tiny syntax error  in the interfaces file will cause it to fail with a very
well hidden error message)

verify with

ethtool -c eth1

2. Have you have disabled AMT / ME in your BIOS setup? This is often present in"corporate"
PC's Like HP/Dell etc. AMT / ME runs an independent process the oversees Ethernet access
so adds latency.
 

Thanks rmu, yes 250um 

Peter, for reference, what would you say is the upper limit of ethernet latency to effectively run a MESA card??

When I'm back at the machine I'll check ethtool and BIOS for AMT/ME
Many thanks!

There really isn't a fixed limit basically you just need to not timeout Ethernet packets
often enough that you get errors. The read timeout is 80% of the servo thread period.
On slower hosts, you can often run a slower servo thread (say 2ms) so you can get away with
fairly lousy ping times.