Messages in this thread |  | | Date | Sat, 30 Nov 2013 23:41:06 +0100 | From | Ondřej Pužman <> | Subject | Re: [PATCH 1/4] pch_gbe: Fix transmit queue management |
| |
> Please format your commit message text to 80 columns.
Ok, no problem. I did not know that 80 columns limitation applies also for commit messages.
> You should be instead preventing the transmit method from being > invoked when it might be possible that a request cannot be > satisfied. This means that at the end of a transmit request, you must > stop the queue if a packet with the maximum number of possible > descriptors cannot be satisfied. Then it is impossible for the > transmit function to be invoked in a situation where it would need to > fail for lack of available transmit descriptors. This is why drivers > decided whether to stop their TX queues based upon calculations > involving MAX_SKB_FRAGS.
Hmm, correct me if I'm wrong ... but the driver and hardware does not support scatter-gather DMA. So fragmented skbs can't be passed to ndo_start_xmit function and each skb passed to the function represents one packet and one descriptor in tx_ring. I do not think that in this caseit makes sense to to involve MAX_SKB_FRAGS in any calculation and the queue should be stopped in the moment when it gets full. But maybe I am missing something, I am no expert in this kind of stuff.
-- Ondrej Puzman
|  |