Subject: Re: [PATCH 3/3] mac80211: Set lower memory limit for non-VHT devices

From: Toke Høiland-Jørgensen <[email-masked]>
Date: Fri, 30 Sep 2016 14:41:42 +0200

Johannes Berg <[email-masked]> writes:

> On Fri, 2016-09-23 at 21:59 +0200, Toke Høiland-Jørgensen wrote:
>> Small devices can run out of memory from queueing too many packets.
>> If VHT is not supported by the PHY, having more than 4 MBytes of
>> total queue in the TXQ intermediate queues is not needed, and so we
>> can safely limit the memory usage in these cases and avoid OOM.
>
> I kinda see the logic here - we really don't need to queue as much if
> we can't possibly transmit it out quickly - but it seems to me we
> should also throw in some kind of limit that's relative to the amount
> of memory you have on the system?

Yes, ideally. That goes for FQ-CoDel as well, BTW. LEDE currently
carries a patch for that which just changes the hard-coded default to
another hard-coded default. Not sure how to get a good value to use,
though; and deciding on how large a fraction of memory to use for
packets starts smelling an awful lot like setting policy in the kernel,
doesn't it?

> I've applied these anyway though. I just don't like your assumption (b)
> much as the rationale for it.

Right, thanks. I'll come up with a better rationale next time ;)

-Toke