Re: [PATCH] [e1000]: Remove unnecessary tx_lock

[Jamal Hadi Salim <hadi@znyx.com>]

On Mon, 2006-07-08 at 17:59 +0200, Edgar E. Iglesias wrote:

> Ok, I thought you wanted the code inside the ifdefs to be considered. If not,
> I guess there is no problem. Yes, the forwarding case does not suffer from
> any deadlocks issues that I am aware of.
> 

>From my tests:
It does _not_ provide any performance improvements and at some point i decided
i didnt want to add more variables to analyze, so i got rid of it; I would have 
had to hand edit the patch to totally remove it; so that why you still see the 
ifdefed out variant.

> No, the deadlock happens only if you don't prune the descriptors. If the host
> sends some data and then goes quite, fdesc < tx_ring->prunet might not be
> true for a long time and skbs will end up sitting in the tx ring indefinitely,
> charging the socket's sndbuf.
> 

Note: I didnt get rid of the rx path pruning. i.e that is still on. It
just prunes lesser descriptors with that change on the tx. So not very
different from before.

I think i may be getting a gist now of the discussion after a re-read; 
while packets are still charged to TCP may have been transmitted they may sit
on the tx ring forever. They will only be pruned if we had netif_stopped
(and even that is not good enough with Jesse's threshold check) or if a
new packet comes in destined for us. 
Did i understand correctly? If yes, i didnt introduce this challenge it
has always been there. I think i understand the suggestion now from
Dave/Herbert to orphan those skbs... 

cheers,
jamal