On Tue, 2006-04-07 at 13:11 -0400, jamal wrote: > CCing anybody who may have stakes on this. Ignore the email if this > doesnt interest you. > Ok, folks - i had deferred this discussion but it bit me in the ass. > I just spend an hour debugging it (and in the process blew up a gbic i > borrowed, so my day aint going well since i actually have to pay for > this and cant really do the testing i was planning to;-<). > > I have a device connected to a e1000 that was erroneously advertising > both tx/rx flow control but wasnt properly reacting to it. > The default setup on the e1000 has rx flow control turned on. > I was sending at wire rate gige from the device - which is about > 1.48Mpps. The e1000 was in turn sending me flow control packets > as per default/expected behavior. Unfortunately, it was sending > a very large amount of packets. At one point i was seeing upto > 1Mpps and on average, the flow control packets were consuming > 60-70% of the bandwidth. Even when i fixed this behavior to act > properly, allowing flow control on consumed up to 15% of the bandwidth. > Clearly, this is a bad thing. Yes, the device in the first instance was > at fault. But i have argued in the past that NAPI does just fine without > flow control being turned on, so even chewing 5% of bandwidth on flow > control is a bad thing.. > > As a compromise, can we declare flow control as an advanced feature > and turn it off by default? People who feel it is valuable and know > what they are doing can turn it off.
I meant turn it on. BTW, As an addendum this default behavior changed around 2.6.16 it seems. cheers, jamal - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
