lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 17 Apr 2019 09:28:51 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Johannes Berg <johannes@...solutions.net>,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        Felix Fietkau <nbd@....name>, linux-wireless@...r.kernel.org,
        Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH 5/5] mac80211: set NETIF_F_LLTX when using intermediate tx queues

Herbert Xu <herbert@...dor.apana.org.au> writes:

> On Tue, Apr 16, 2019 at 11:02:50AM +0100, Toke Høiland-Jørgensen wrote:
>> 
>> As explained at great length here:
>> https://www.usenix.org/conference/atc17/technical-sessions/presentation/hoilan-jorgesen
>> (you already know that of course, Johannes)
>
> I can understand that wireless needs its own queueing scheme, but it
> still seems wrong to place that under net/mac80211 as opposed to
> having it as a first-class citizen under net/sched.

This is because we need to resolve the MAC-layer destination station (or
rather, TID) and tie the queueing to that, because of aggregation. We
also use the queueing structure for scheduling stations to achieve
airtime fairness. Both of these would be decidedly non-trivial to pull
up to the qdisc layer. Rather, having them in mac80211 means drivers
don't need to do their own ad-hoc queueing (which was the case before,
leading extra bufferbloat).

Most of the actual queueing structure code lives in
include/net/fq_impl.h, though, so it's not actually that
mac80211-specific. I've been thinking about porting the relevant qdiscs
to use the same code, but I'm not sure that it's worth the trouble.

-Toke

Powered by blists - more mailing lists