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From: "Toke Høiland-Jørgensen" <toke@toke.dk>
To: Jonathan Morton <chromatix99@gmail.com>,
	dave.collier-brown@indexexchange.com
Cc: bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] What's a good non-intrusive way to look at bloat (and perhaps things like gout (:-))
Date: Thu, 04 Jun 2020 12:56:48 +0200	[thread overview]
Message-ID: <87k10njdzj.fsf@toke.dk> (raw)
In-Reply-To: <B55EE88E-4AA5-4306-A3E1-0AC0F2B67AD6@gmail.com>

Jonathan Morton <chromatix99@gmail.com> writes:

>> On 4 Jun, 2020, at 1:21 am, Dave Collier-Brown <dave.collier-brown@indexexchange.com> wrote:
>> 
>> We've good tools to measure network performance under stress, by the
>> simple expedient of stressing it, but is there a good approach I
>> could recommend to my company to monitor a bunch of reasonably modern
>> links, without the measurement significantly affecting their state?
>> 
>> I don't mind increasing bandwidth usage, but I'm downright grumpy
>> about adding to the service time: I have a transaction that times out
>> for gross slowness if it takes much more that an tenth of a second,
>> and it involves a scatter-gather interaction with at least 10
>> customers in that time.
>> 
>> I'm topically interested in bloat, but really we should understand
>> "everything" about our links. If they can get the bloats like cattle,
>> they can probably get the gout, like King Henry the Eighth (;-))
>> 
>> My platform is Centos 8, and I have lots of Smarter Colleagues to
>> help.
>
> My first advice would be to browse pollere.net for tools - like pping
> (passive ping), which monitors the latency of flows in transit. That
> should give you some interesting information without adding any load
> at all. There is also connmon (https://github.com/pollere/connmon).

Ah, good idea, totally forgot about Kathy's tools! :)

I figure one could probably implement something like connmon in eBPF (as
an XDP or TC hook program) and have it run as an always-on monitor with
fairly low overhead. Dave, if you have development resources to throw at
this, I'll be happy to help with pointers on how to get the eBPF bits
working. I believe CentOS 8.2+ should have the needed kernel support...

Of course, you could also just use the connmon utility as-is if you have
CPU cycles to spare for the extra overhead (it looks like it's using
libpcap to capture the packets and process them in userspace).

-Toke

  reply	other threads:[~2020-06-04 10:56 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-03 22:21 Dave Collier-Brown
2020-06-03 22:30 ` Jonathan Morton
2020-06-04 10:56   ` Toke Høiland-Jørgensen [this message]
2020-06-04 12:25     ` Dave Collier-Brown

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