Re: [PATCH] mac80211: Change default tx_sk_pacing_shift to 7

[Johannes Berg <johannes@sipsolutions.net>]

On Fri, 2019-02-22 at 14:06 +0100, Toke Høiland-Jørgensen wrote:
> Johannes Berg <johannes@sipsolutions.net> writes:
> 
> > Toke Høiland-Jørgensen 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 buffering
> > > and picked 4 ms instead of 8. This was probably wrong; those 2 ms of extra
> > > buffering makes a larger difference than I thought.
> > > 
> > > 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.
> > > 
> > > Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> > 
> > Patch applied to wireless.git, thanks.
> > 
> > a41f56b9a17a (HEAD -> mac80211) mac80211: Change default
> > tx_sk_pacing_shift to 7

This mess came from Kalle's tool btw, so I can't really use it yet :-)

> 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?

Just update the value, no need to backport the hook.

johannes