[Bloat] [bbr-dev] Aggregating without bloating - hard times for tcp and wifi

[Bob McMahon]

Does the TSQ code honor no-aggregation per voice access class or
TCP_NODELAY where the app making the socket write calls knows that the WiFi
aggregation isn't likely helpful? Sorry, my Linux stack expertise is quite
limited.

Bob

On Tue, Nov 22, 2022 at 12:53 PM Toke Høiland-Jørgensen <toke at toke.dk>
wrote:

> Neal Cardwell via Bloat <bloat at lists.bufferbloat.net> writes:
>
> > On Tue, Nov 22, 2022 at 2:43 PM 'Bob McMahon' via BBR Development <
> > bbr-dev at googlegroups.com> wrote:
> >
> >> Thanks for sharing this. Curious about how the xTSQ value can be set?
> Can
> >> it be done with sysctl?
> >>
> >> *We continue our analysis by using the ms-version of TSQ patch, which
> >> enables the tune of the TSQ size allowing each TCP variant to enqueue
> more
> >> than 1 ms of data at the current TCP rate. In particular, we allow to
> >> enqueue the equivalent of x ms of data, naming each test xTSQ, with x
> being
> >> an integer value. It is important to notice that this patch has been
> >> included in the Linux kernel mainline, and each Wi-Fi driver can now set
> >> the desired xTSQ value**.*
> >>
> >
> > I believe they are setting the xTSQ value using the sk_pacing_shift
> field,
> > which was added here:
> >
> >
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3a9b76fd0db9f0d426533f96a68a62a58753a51e
> >
> > AFAIK the intent is only for drivers to set that, and there's no sysctl
> for
> > that, but of course you could add a sysctl for testing if you wanted.
> > :-)
>
> Yup, indeed this is what mac80211 fiddles with:
> https://elixir.bootlin.com/linux/latest/source/net/mac80211/main.c#L739
> https://elixir.bootlin.com/linux/latest/source/net/mac80211/tx.c#L4156
>
> AFAICT, no in-tree drivers override the value set by mac80211.
>
> I believe the tests in that paper were conducted with this series
> applied:
>
> https://lore.kernel.org/all/20180105113256.14835-1-natale.patriciello@gmail.com/
>
> -Toke
>

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