Hi there

Is there some way to read the actual values for the coalesce options
back from the NIC? To be specific, I'm interested in the value of ITR
on a 82574L chip. I suspect it does not match with the value that I
get from "ethtool -c". Reading back from userspace, without compiling
a lot of stuff if possible...

Some background: I use ifupdown from Debian to configure an Ethernet
interface. I want to disable all coalesce settings. What I've done is
to call ethtool with the required parameter from a script in if-up.d,
which is run right after the interface gets set to up (using something
like ifconfig up). However, judging from my applications behaviour I
think that the default "rx-usecs 3" is still active, even though
ethtool -c tells me it is set to '0'. After changing it to "1" and
then back to "0", my application works properly (change to one is
required because ethtool will not write the same value again).

I suspect some kind of race between the kernel thread bringing up the
interface and my script calling ethtool, and I hope to verify this by
seeing the actual values of coalesce that are used.

I use a dated 3.12 with PREEMPT_RT patch.

Christoph

PS Please CC

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