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Date: Wed, 19 Oct 2011 11:27:43 -0700
Message-ID: <CA+yqC4be-6h-AY9G6YJCtNBRFQ51UyQNxFtJfG85gqZufiDF1g@mail.gmail.com> (sfid-20111019_202755_251206_94B2901E)
Subject: Re: [ath5k-devel] Performance regression between Madwifi/net80211 and ath5k/mac80211
From: Sam Leffler <sleffler@google.com>
To: Pavel Roskin <proski@gnu.org>
Cc: Adrian Chadd <adrian@freebsd.org>,
	Joerg Pommnitz <pommnitz@yahoo.com>,
	Bob Copeland <me@bobcopeland.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	"ath5k-devel@lists.ath5k.org" <ath5k-devel@venema.h4ckr.net>
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On Wed, Oct 19, 2011 at 8:55 AM, Pavel Roskin <proski@gnu.org> wrote:
> On Wed, 19 Oct 2011 19:33:53 +0800
> Adrian Chadd <adrian@freebsd.org> wrote:
>
>> .. does madwifi have that net80211 "aggressive mode" by default, where
>> it overrides the best-effort WME queue parameters to allow for
>> bursting?
>
> I tried madwifi-0.9.4 snapshot on a CM9 card, and I got:
>
> # iwpriv ath0 get_abolt
> ath0 ? ? ?get_abolt:218
>
> 218 is 0xda, which means that the following capabilities are enabled:
>
> IEEE80211_ABOLT_TURBO_PRIME
> IEEE80211_ABOLT_FAST_FRAME
> IEEE80211_ABOLT_BURST
> IEEE80211_ABOLT_XR
> IEEE80211_ABOLT_AR
>
> And those are not enabled:
>
> IEEE80211_ABOLT_TURBO_G
> IEEE80211_ABOLT_COMPRESSION
> IEEE80211_ABOLT_WME_ELE
>
> I would just unset all capabilities and retry.
>
>> I see exactly that difference in FreeBSD (33mbit vs 22mbit) when I
>> disable that aggressive mode code.

Bursting will get you to ~28 and FF's are likely the reset (no dynamic
turbo on freebsd).  It would be nice to have control in linux to
explicitly turn on/off bursting but the usual way people do it is to
negotiate wmm and force the txop limit.

BTW whenever you see a performance difference the first thing to look
at is packets/sec.  I've not found any linux tools that give me this a
la athstats/wlanstats on freebsd.

-Sam