On Fri, 2019-06-14 at 13:31 +0200, Stanislaw Gruszka wrote: > On Fri, Jun 14, 2019 at 12:20:59PM +0200, Johannes Berg wrote: > > On Fri, 2019-06-14 at 12:11 +0200, Lorenzo Bianconi wrote: > > > > > Looking at __ieee80211_amsdu_copy() now I got why other drivers copy hdrlen + > > > 8, thx :) > > > In our case reuse_frag is true in __ieee80211_amsdu_copy, so we will end up > > > copying 32B + ether_len. Anyway I think 32 is a little bit too low and we could get > > > better performances increasing it a little bit. > > > A typical use case (e.g IPv6 + TCP): > > > > > > IPv6 = 40B, TCP = 32B --> so 72B..I guess 128B is a good value :) > > > @Felix, Johannes: what do you think? > > > > I think while we might *allocate* more, I don't think we should *copy* > > more, since then the TCP payload will no longer be in pages. > > > > It'd probably be better to implement leaving enough tailroom (allocate > > 128), but copying nothing, unless the *entire* packet fits. > > iwl4965 put entire packet in fragment in il4965_pass_packet_to_mac80211() . > Initially I thought this is a bug, since mac80211 require header be > in the linear area, but looks like ieee80211_rx_monitor() copy header > before rest of mac80211 check it, so 4965 is fine. Mac80211 should not assume anything about header being present or not, just like the rest of the network stack. > Anyway I think the driver should put ieee80211 header in linear area > and iwlwifi & mt7601u implementation is somewhat optimal. Yes, it's just an optimisation to do the copy-break (copy small packets completely) or to copy the header already (since we may have better ways to do so than skb_copy_bits if we still have a virt pointer to the page, rather than just the page pointer). johannes
