On Fri, Mar 11, 2011 at 12:13 AM, Guy, Wey-Yi <wey-yi.w.guy@xxxxxxxxx> wrote: >> (1) Why does iwlwifi default to an aggregation frame limit of 31? I >> didn't see any negative effects from 63 frame limit and performance >> improved dramatically > if I remember correctly, we change from 63 to 31 while we have some 11n > performance issue. even later we found out frame limit is not the main > reason of low tpt, but we did not change it back since at the time we > did not see any performance different, I believe we can use different > frame limit, but I will prefer make it more flexible, maybe something > could be change by either module parameter or debugfs. Also I am not > sure are there any behavior differences between different devices and > different versions of ucode. 63 hasn't hurt me yet, though the scheduler still does occasionally send a 64th frame that shifts the reorder buffer's window. Is there a chance that 64 will work as a max? 63 seems an odd choice. >> (3) mac80211's reorder buffer code could probably also be relaxed. It >> probably wouldn't hurt to have the buffer be twice the transmitter's >> advertised buffer, and might compensate for devices that don't >> properly honor frame limits. Also, mac80211 only flushes the reorder >> buffer every 100 ms. That seems like a LONG time given that batches >> are limited to 4ms -- 100ms is room for at least 10, maybe 20 >> retransmissions to attempt to fill in the holes(!). Removing the check here <https://github.com/mirrors/linux-2.6/blob/master/net/mac80211/agg-rx.c#L231> essentially forces the receive buffer to be 64 frames long. This works just fine for me (iwl5300 TXer and RXer) and would seem to be appropriate for any transmitter window. If the transmitter uses a window of, say, 31 frames and also honors its limit, then I think the only wasted space would be 33 pointers to skb's at the transmitter side. I didn't see any degradation using an ath9k+minstrel_ht transmitter with this change. Dan -- 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
