Cake - FQ_codel the next generation
 help / color / mirror / Atom feed
From: Andy Furniss <adf.lists@gmail.com>
To: Jonathan Morton <chromatix99@gmail.com>
Cc: Cake@lists.bufferbloat.net
Subject: Re: [Cake] low bandwidth default params best effort vs voice latency.
Date: Sun, 5 Mar 2017 12:37:38 +0000	[thread overview]
Message-ID: <325f92c7-e867-6511-f5c9-8f1f6f6abe2f@gmail.com> (raw)
In-Reply-To: <95D56BA5-0C5E-4D2E-B28F-A8C957B5F65D@gmail.com>

Jonathan Morton wrote:
> Okay, I think I’ve worked out what is happening.
>
> At 250KB/s, it takes 6ms to get one 1500-byte bulk packet down the
> pipe.  This is unavoidable, so having a bulk flow competing with your
> game traffic will always increase your peak latency by that much.
>
> With three independent game streams in play, it’s possible for them
> all to transmit simultaneously *and* to coincide with a bulk packet
> having just been sent.  With overheads, it will take a total of 8.5ms
> to get all four packets through.  This corresponds nicely to your
> best-effort results; you’re getting very close to the theoretical
> best performance there.

Yea, the pleasures of low bandwidth - not that I would have called 2mbit
low a few years ago, and 8ms isn't that bad.

Historically, I once had an asymmetric mss clamping setup so up tcp
was smaller than down.

> So Diffserv marking actually can’t improve your performance in this
> particular case.  But it shouldn’t make it worse either.  You’re
> actually seeing a nearly 6ms increase in peak latency, which
> corresponds neatly to an additional bulk packet ending up ahead of
> the game traffic in the queue.
>
> That’s not supposed to happen, but I think I can see how it *can*
> happen with the current Diffserv logic.  It’s a weighted DRR, much
> like what is used between flow queues a little further down - but it
> *doesn’t* have a special bonus for sparse tins.  That’s something I
> clearly need to fix.
>
> To help remind me, please do open an issue on the Github project.

OK, I opened
https://github.com/dtaht/sch_cake/issues/52

      parent reply	other threads:[~2017-03-05 12:37 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-04 18:21 Andy Furniss
2017-03-04 18:45 ` Jonathan Morton
2017-03-04 19:28   ` Andy Furniss
2017-03-04 20:27 ` Jonathan Morton
2017-03-04 23:05   ` Dave Taht
2017-03-05 12:43     ` Andy Furniss
2017-03-05 12:37   ` Andy Furniss [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: https://lists.bufferbloat.net/postorius/lists/cake.lists.bufferbloat.net/

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=325f92c7-e867-6511-f5c9-8f1f6f6abe2f@gmail.com \
    --to=adf.lists@gmail.com \
    --cc=Cake@lists.bufferbloat.net \
    --cc=chromatix99@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox