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Message-ID: <b900d560d5dabaea1a9faf9d8ff8a019ed813e25.camel@sipsolutions.net>
Subject: Re: [PATCH] mac80211: Simplify queue selection
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Felix Fietkau <nbd@nbd.name>,
        Alexander Wetzel <alexander@wetzel-home.de>
Cc:     linux-wireless@vger.kernel.org,
        Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= <toke@kernel.org>
Date:   Tue, 10 May 2022 21:06:43 +0200
In-Reply-To: <54589d98-882c-cee4-dd6d-140d50f400d0@nbd.name>
References: <20220510155828.9406-1-alexander@wetzel-home.de>
         <54589d98-882c-cee4-dd6d-140d50f400d0@nbd.name>
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On Tue, 2022-05-10 at 18:10 +0200, Felix Fietkau wrote:
> On 10.05.22 17:58, Alexander Wetzel wrote:
> > Let iTXQ drivers also register four queues in netdev and move queue
> > assignment to ndo_select_queue(), like it's done for other drivers.
> > 
> > This gets rid of a special case in mac80211 and also increases the
> > chance that when we call skb_get_hash() the skb is still hot in the CPU
> > buffers.
> > 
> > Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
> 
> This has the disadvantage of requiring a redundant sta lookup in the tx 
> path for iTXQ drivers. I think the CPU cost of that one is probably 
> higher than any potential gain from calling skb_get_hash a bit earlier.
> 

However, that's independent - we can still calculate the hash there, and
then bail out, i.e. put it right before the "if (wake_tx_queue) return"
part, no?

OTOH we don't even need the hash in the other cases, do we?

johannes