On Tue, 2011-04-19 at 03:26 -0700, Lennert Buytenhek wrote: > On Tue, Apr 19, 2011 at 03:38:17PM +0530, Nishant Sarmukadam wrote: > > > > > This is in preparation to support life time expiry of packets in the > > > > hardware to avoid head-of-line blocking where a slow client can > > > > hog a tx queue and affect the traffic to a faster client from the same > > > > queue. Time stamp the packets in driver to allow dropping them in the > > > > hardware if they are queued for more than 500ms. > > > > > > > > Since queues are not being stopped now, we need to be prepared for > > > > a situation where packets hit the driver after the queues are full. > > > > Drop all such packets in the driver itself. > > > > > > What this patch seems to do is: don't propagate queue start/stop > > > indications to mac80211, and if a packet is handed to mwl8k for > > > transmission while a TX queue is full, just drop it in the driver. > > > (This doesn't seem to correspond with the commit message.) > > > > We were invoking mac80211 routines to start/stop tx queues. Since we do > > not call these routines now, the queues will not be stopped anymore. > > Hence, packets that enter the driver after the corresponding queue is > > full, need to be dropped. This is mentioned in the commit description. > > Please let me know if I am missing something. > > Maybe it's me, but to me, the commit message seems to say that queue > starting/stopping is already not being done anymore by mwl8k, and > because of that, we need to drop packets that are being transmitted > in the driver when the TX queue is full, which this patch does. Ok, I will try to address this in patch set V2. > > > > > But since the driver still has an accurate idea of TX queue fullness > > > (i.e. it's not as if at transmit time, you go and transparently reclaim > > > TX queue entries), why do you need to start/stop mac80211 TX queues at > > > all? Won't it still work fine without deleting that logic? > > > > We need to timestamp all tx packets. If we stop the queues, packets will > > be queued up outside the driver (in queue full conditions). Since we > > will be able to timestamp the packets only after they hit the driver, > > the timestamp will be less accurate since we cannot consider the time > > the packets spent in the queues outside the driver. > > This is a fair argument, and this really should be in the commit message. I will incorporate this in patch set V2. -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
