[Starlink] Starlink hidden buffers

[Dave Collier-Brown]

On 5/24/23 10:49, Michael Richardson via Starlink wrote:

> It saved your bacon, but yeah, like all other resilient protocols (DNS,
> Happy Eyeballs) tends to hide when one option is failing :-)
>
>      > pure AQM, in the case above, since that flood was uncontrollable, would
>      > have resulted in a 99.99% or so drop rate for all other traffic. While
>      > that would have been easier to diagnose I suppose, the near term
>      > outcome would have been quite damaging.
>
> What this says is that fq_codel doesn't have enough management reporting
> interfaces.   Going back 25 years, this has always been a problem with home
> routers: ntop3 is great, but it's not easy to use, and it's not that
> accessible, and it often can't see things that move around.

Over and above management reporting, the deleterious effect should be
both visible and capable of being reasoned about by the community.

A classic example from Unix is that memory exhaustion and thrashing
causes a sudden increase in IO to the swap device, followed by a queue
building up and the dis slowing down.

The latter is something one usually has alerts on, to tell the sysadmin
if a disk is misbehaving. Getting a "disk is too busy" from the swap
device tends to cause the sysadmin to ask themselves what could cause
that, and realize that something is swapping. That send then off looking
for the root cause.

Yet another case of "belt and suspenders" (;-))

--dave

--
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
dave.collier-brown at indexexchange.com |              -- Mark Twain


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