mac80211 and kernel 3.8.13 1/2 speed as with madwifi and kernel 2.6.23

[Beat Meier <mbe_shop@swiss-wireless.com.ar>]

Hello

I'm trying to use again mac driver instead of old madwifi driver for
atheros cards.
I have following problem.
On Clients using mac80211 (wpa_supplicant) it's just fine but if you use
it with hostapd you have about 1/2 speed
as with madwifi. Problem could be also kernel<->wireless driver issue.
With madwifi I'm using an old kernel 2.6.23 (voyage-0.5 distribution)
and with mac80211 a new kernel 3.8.13 (voyage-0.9.1)

Example:
5.5km 5.8GHz link 2xAlix board, 2xWLM54AGP23 card, 2x Hyperlink 27dbi
grids, wireless card speed set to 24M
to get max. signal on this cards...
Signal on both sites is -60

With madwifi driver on both site you get 12.8Mbps/14.5Mbps download/upload
madwifi driver on server, mac80211 on client you still get 13.4/13.8Mbps
BUT if you use mac80211 on ap master mode with hostap you get only
7Mbps/5.5Mbps.
Tried all 4 constellation (old/new, new/old, new/new and old/old) and
the issue is only
if the hostapt is running with new kernel/mac80211

Same stuff on other links with other cards like CM9.

What I have seen is that with madwifi driver the cpu is 90-100% cpu
usage with ksoftirqd
with mac80211 not...
Could this be a kernel interrupt issue? Are there several policies which
changed with kernel?

Anyone having same issue?

Greetings and thanks