Ross Walker wrote:
On Wed, Aug 12, 2009 at 7:23 PM, Ross Walker<[email protected]> wrote:
On Wed, Aug 12, 2009 at 5:56 PM, Ross Walker<[email protected]> wrote:
On Wed, Aug 12, 2009 at 5:44 PM, Peter Memishian<[email protected]> wrote:
> set dld:dld_opt = 2
Yikes! Perhaps you're looking for the no-poll or no-softring capabilities
in /kernel/drv/dld.conf? (Not to say those will address your original
goal, but they're better than twiddling implementation artifacts via
/etc/system.)
Thanks for the pointer.
Don't know why I didn't think of looking there first, guess it's a bad
case of Google Monkey see, Google Monkey do...
Ok, I set the no_poll=1 and no-softring=1 in the dld.conf and it made
no real noticeable difference.
The data-path that we introduced as part of Crossbow will let packets go
through the same context as long as there's no backlog for best latency.
These dld properties were never meant to be public interfaces for tuning.
I'm thinking that the igb driver is doing some interrupt coalesence
here, but I can't find any options to disable or tune it.
On a hunch I thought I'd run the igb module through strings and see if
there was anything interesting and found these.
intr_throttling
rx_limit_per_intr
intr_force
I don't have any docs on these, so it's going to be interesting to see
how they work.
I think I'll try the intr_throttling option first as it looks most promising.
http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/io/igb/igb_main.c
has references to a throttling property configurable via igb.conf. It's
also not a public interface, but if you want to play the source is there :-)
In general the idea is for the drivers to use aggressive
blanking/throttling out of the box for best latency, and let the polling
in the stack kick-in as the load increases to dynamically disable
interrupts and schedule incoming packets according to the load. Some
drivers might not be tuned for the best out-of-the-box latency.
Nicolas.
-Ross
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