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Message-ID: <13154ef7-63ee-cfe7-3ebb-a7f1120985b6@wetzel-home.de>
Date:   Tue, 10 May 2022 18:13:31 +0200
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Subject: Re: [PATCH] mac80211: Simplify queue selection
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To:     Felix Fietkau <nbd@nbd.name>,
        Johannes Berg <johannes@sipsolutions.net>
Cc:     linux-wireless@vger.kernel.org,
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        <toke@kernel.org>
References: <20220510155828.9406-1-alexander@wetzel-home.de>
 <54589d98-882c-cee4-dd6d-140d50f400d0@nbd.name>
From:   Alexander Wetzel <alexander@wetzel-home.de>
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On 10.05.22 18:10, 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.

Found that one, yes. But why do we then not drop ndo_select_queue() for 
all drivers?

Or maybe just call skb_get_hash() in ndo_select_queue()... But I guess 
then it would make more sense to move the ndo_select_queue() into 
netdev, so all drivers get the optimization.

Alexander