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From: Dave Taht <dave.taht@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: codel@lists.bufferbloat.net
Subject: Re: [Codel] usage of 'count' in codel
Date: Sun, 6 May 2012 11:26:56 -0700	[thread overview]
Message-ID: <CAA93jw6ZTi6p2jQb=RB0PgGUoTjQgRLr20X2FJiWHHYzQqWNFQ@mail.gmail.com> (raw)
In-Reply-To: <1336328140.3752.2014.camel@edumazet-glaptop>

On Sun, May 6, 2012 at 11:15 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Sun, 2012-05-06 at 13:20 -0400, Jim Gettys wrote:
>
>
>
>> I sort of think that having some upper queue time bound makes sense, if
>> only to ensure that TCP's quadratic (un)responsiveness never gets out of
>> hand.  But we agreed that having an implementation we could play with to
>> observe reality would likely be better than hand-waving with no
>> experience about how long the queue should be allowed to grow.
>
> Even with normal tcp flows, codel is not responsive enough and too
> conservative as is.
>
> drop_next = control_law(drop_next)   with interval/sqrt(count)
> increments ?
>
> Something is _really_ wrong.
>
> Thats few drops per second when we need far more than this.
>
> interval = 100ms so you need count = 10000 to reach the rate of one drop
> per ms, regardless of the link capacity.

with the >>1 change.

At 100Mbit I see observed delays that aren't bad, and queue lengths
that are quite nice.

That's with ethernet ratcheted down to 100Mbit with ethtool,
no TSO/GSO with BQL.

1 netperf, 5ms delay on ping RTT
30, about ~12ms

And in both cases the box on the other end is in drop tail.

I don't trust htb at this point, if that's what you are using?

qdisc codel 8007: root refcnt 2 limit 1000p minbytes 1514 target 5.0ms
interval 100.0ms
 Sent 5995574344 bytes 3975635 pkt (dropped 145097, overlimits 0
requeues 1842324)
 backlog 86298b 58p requeues 1842324
  count 4549 delay 6.7ms drop_next 580us

What do you see at 10GigE with like 60 netperfs?

(god, can you even drive 10GigE that hard? me is jealous of hardware.
 I CAN get to where I can drive GigE now, I just want to update both
 sides of the connection to be codel capable, and am waiting on a
 more final patch)


>
> control loop has no input on time of residence of packets.
>
>
>



-- 
Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608
http://www.bufferbloat.net

  reply	other threads:[~2012-05-06 18:26 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAA93jw7bnQED7QXc_jgsEyf-ydR0Bo-OazBZOTXDQ9nYYCgpJw@mail.gmail.com>
     [not found] ` <1336281092.3752.982.camel@edumazet-glaptop>
     [not found]   ` <1336283203.3752.1032.camel@edumazet-glaptop>
     [not found]     ` <1336315913.3752.1598.camel@edumazet-glaptop>
     [not found]       ` <1336324134.3752.1825.camel@edumazet-glaptop>
2012-05-06 17:20         ` Jim Gettys
2012-05-06 17:58           ` dave taht
2012-05-06 18:25             ` Simon Barber
2012-05-06 18:41               ` Dave Taht
2012-05-06 18:48               ` Eric Dumazet
2012-05-06 18:15           ` Eric Dumazet
2012-05-06 18:26             ` Dave Taht [this message]
2012-05-06 18:49               ` Eric Dumazet
2012-05-06 19:15                 ` Dave Taht
2012-05-06 19:47                   ` Eric Dumazet

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