On Mon, Feb 14, 2011 at 4:17 AM, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > On Sun, 2011-02-13 at 09:56 -0800, Nathaniel J. Smith wrote: >> This patch estimates how long it takes the hardware to transmit one >> packet (by comparing each packet's queue residency time to the number >> of packets it had to wait behind), and then further smooths these >> estimates with an EWMA. Then, it uses the estimated packet >> transmission time to choose the maximum queue size that will still >> produce reasonably bounded queue residency times, given current >> conditions. > > This sounds nice -- but couldn't it just as well be implemented in > mac80211, at least for most devices (that have accurate TX status > reporting)? I don't know. I take it you're imagining a scheme where mac80211 keeps a hash table or similar of all packets that have been queued to the device, and does its own tx rate estimation and calls start/stop_queue as needed? If that works, then it would be lovely. (Heck, it should probably go in the generic net layer eventually; ethernet cards have the same problem.) But there are enough complications around multiqueue devices, packet aggregation strategies, interrupt mitigation, etc., that I don't think I sit down and write this fully general solution myself, at least not without a lot more experience with the needs of different devices. So this patch is intended as a start. On Mon, Feb 14, 2011 at 7:46 AM, wwguy <wey-yi.w.guy@xxxxxxxxx> wrote: > Hi Nathaniel, [...] > should the high_mark get reset when interface up or queue reset. Hi Wey, I thought about that, but I can't see what difference it would make. If we have no information about connection quality, then any high_mark is as good as any other (and if anything, the previous connection's quality is probably as good an estimate as we have, since people often reconnect to the same network repeatedly after suspend, etc.). And in any case, once connected, we should adapt quite quickly (esp. when using the uplink heavily, which is the only time when the queue size has an effect), so our starting value should hardly matter. But I have no objection to resetting it if that seems cleaner somehow. -- Nathaniel -- 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
