On (08/08/14 11:46), David Miller wrote: > Date: Fri, 08 Aug 2014 11:46:01 -0700 (PDT) > From: David Miller <davem@xxxxxxxxxxxxx> > To: sowmini.varadhan@xxxxxxxxxx > Cc: david.stevens@xxxxxxxxxx, karl.volz@xxxxxxxxxx, > sparclinux@xxxxxxxxxxxxxxx > Subject: Re: soft-lockups in sunvnet > X-Mailer: Mew version 6.5 on Emacs 24.1 / Mule 6.0 (HANACHIRUSATO) > > From: Sowmini Varadhan <sowmini.varadhan@xxxxxxxxxx> > Date: Fri, 8 Aug 2014 14:39:39 -0400 > > > So you are able to successfully trigger the tasklet from vnet_event(), > and have that tasklet do the queue wakeups? yes. > But removing the backoff logic from __vnet_tx_trigger() does work, > right? It "works" to the extent that it recovers. You get a lot more errors, much more easily, though - thus throughput sinks. I dont know how the heuristics were determined, but they seem to help... > I don't think vnet_walk_rx() is really able to handle any kind of real > failures from vnet_send_ack() properly. If we send one or more > VIO_DRING_ACTIVE ACKs and then can't send the VIO_DRING_STOPPED one > out, the ring will likely be left in an inconsistent state. I just found out last week that you dont actually need to set the VIO_ACK_ENABLE (and thus trigger the ACTIVE acks)- evidently the protocol is such that the STOPPED ldc message is sufficient. So one patch that I'm working on lining up (after due testing etc) is to not set VIO_ACK_ENABLE in vnet_start_xmit- it also helps perf slightly because it reduces the trips through ldc (and potentail for filling up the ldc ring). --Sowmini -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
