From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     linux-wireless@vger.kernel.org,
        Ben Greear <greearb@candelatech.com>,
        Grant Grundler <grundler@google.com>,
        Kalle Valo <kvalo@codeaurora.org>, wgong@qti.qualcomm.com,
        ath10k@lists.infradead.org, wgong@codeaurora.org,
        Kan Yan <kyan@google.com>
Subject: Re: [PATCH] mac80211: Change default tx_sk_pacing_shift to 7
In-Reply-To: <E1gx9x3-0002j0-1J@sipsolutions.net>
References: <20190221172936.21816-1-toke@redhat.com> <E1gx9x3-0002j0-1J@sipsolutions.net>
Date:   Fri, 22 Feb 2019 14:06:35 +0100
Message-ID: <87lg28vup0.fsf@toke.dk>
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Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

Johannes Berg <johannes@sipsolutions.net> writes:

> Toke H=C3=B8iland-J=C3=B8rgensen wrote:
>
>> When we did the original tests for the optimal value of sk_pacing_shift,=
 we
>> came up with 6 ms of buffering as the default. Sadly, 6 is not a power of
>> two, so when picking the shift value I erred on the size of less bufferi=
ng
>> and picked 4 ms instead of 8. This was probably wrong; those 2 ms of ext=
ra
>> buffering makes a larger difference than I thought.
>>=20
>> So, change the default pacing shift to 7, which corresponds to 8 ms of
>> buffering. The point of diminishing returns really kicks in after 8 ms, =
and
>> so having this as a default should cut down on the need for extensive
>> per-device testing and overrides needed in the drivers.
>>=20
>> Signed-off-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@redhat.com>
>
> Patch applied to wireless.git, thanks.
>
> a41f56b9a17a (HEAD -> mac80211) mac80211: Change default
> tx_sk_pacing_shift to 7

Cool, thanks! What's the easiest way to backport this? I figure it's
easier to just update sk_pacing_shift_update() in tx.c for 4.19 (which
predates the addition of the driver override hook); shall I just send a
separate patch to stable for that? Or do we need to backport the driver
override hook as well?

-Toke