Date: Sat, 19 Feb 2011 15:19:45 +0530
From: Vasanthakumar Thiagarajan <vasanth@atheros.com>
To: Johannes Berg <johannes@sipsolutions.net>
CC: Vasanth Thiagarajan <Vasanth.Thiagarajan@Atheros.com>,
	"linville@tuxdriver.com" <linville@tuxdriver.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH] ath9k: Implement op_flush()
Message-ID: <20110219094943.GA16465@vasanth-laptop>
References: <1298106822-9411-1-git-send-email-vasanth@atheros.com> <1298107440.3725.8.camel@jlt3.sipsolutions.net>
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On Sat, Feb 19, 2011 at 02:54:00PM +0530, Johannes Berg wrote:
> On Sat, 2011-02-19 at 01:13 -0800, Vasanthakumar Thiagarajan wrote:
> > When op_flush() is called with no drop (drop=false), the driver
> > tries to tx as many frames as possible in about 100ms on every
> > hw queue. During this time period frames from sw queue are also
> > scheduled on to respective hw queue.
> 
> Given how long HW queues currently are, I wouldn't set the timeout to
> 100ms -- mac80211 has no expectation how long this will take, although
> 100ms seems pretty long I'm not sure it'll always be sufficient?

It is not that we wait for 100ms always, we return as soon as
possible if there are no pending frames in sw/hw queues. I never
hit this timeout though. In the worst case there can be 128 (4 aggr)
frames pending in sw queue and 2 in hw queue. If we assume each one of
these aggregates has 4ms duration, we at least need 24ms air time at
the lowest rate. If they are not part of AMPDU, it would take a
little bit more I think. So, probably we can give ~40ms timeout,
is that reasonable?. If i'm reading the code correctly, iwlwifi
seems to use 2000ms.

vasanth