Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <bcdb70fe-de2f-a46b-66e2-ff92f8b86425@nbd.name>
Date:   Sat, 18 Jun 2022 10:51:18 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0)
 Gecko/20100101 Thunderbird/91.10.0
Subject: Re: [PATCH v2 1/4] mac80211: fix overflow issues in airtime fairness
 code
Content-Language: en-US
From:   Felix Fietkau <nbd@nbd.name>
To:     linux-wireless@vger.kernel.org
Cc:     johannes@sipsolutions.net, toke@kernel.org
References: <20220611200106.34319-1-nbd@nbd.name>
In-Reply-To: <20220611200106.34319-1-nbd@nbd.name>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 11.06.22 22:01, Felix Fietkau wrote:
> The airtime weight calculation overflows with a default weight value of 256
> whenever more than 8ms worth of airtime is reported.
> Bigger weight values impose even smaller limits on maximum airtime values.
> This can mess up airtime based calculations for drivers that don't report
> per-PPDU airtime values, but batch up values instead.
> 
> Fix this by reordering multiplications/shifts and by reducing unnecessary
> intermediate precision (which was lost in a later stage anyway).
> 
> The new shift value limits the maximum weight to 4096, which should be more
> than enough. Any values bigger than that will be rejected
> 
> Signed-off-by: Felix Fietkau <nbd@nbd.name>
Please don't merge this series yet. I'm still investigating reports of 
regressions caused by it.

- Felix