[Cerowrt-devel] Comcast Uplink Buffers
William Katsak
wkatsak at gmail.com
Thu Mar 5 14:52:53 EST 2015
Alright thanks, I'll run some more tests tonight after other people are
done using the connection.
Regarding your other questions:
Yes, the machine I am using to test is wired to the Atom via a small
netgear managed switch.
The only thing that is running on this Atom box is routing, iptables,
unbound, and DHCP.
Thanks,
-Bill
On 03/05/2015 02:05 PM, Aaron Wood wrote:
> Bill,
>
> I'd recommend setting the bandwidth values low (very low) at first, just
> to establish that the setup is working correctly. I'm able to get
> better control of latency at those bitrates on an WNDR3800:
>
> http://burntchrome.blogspot.com/2014/05/fixing-bufferbloat-on-comcasts-blast.html
>
> I'd start slow, and then start raising the limits until you see issues.
>
> But it's possible something else is causing issues. Is your netperf
> source wired to the Atom? (for bandwidth levels that ruler flat, I
> normally assume wired. I've seen wifi give odd 30ms jumps in latency,
> but those normally come with an drop in bandwidth as well).
>
> What else is running on the Atom box?
>
> -Aaron
>
>
>
>
> On Thu, Mar 5, 2015 at 7:49 AM, William Katsak <wkatsak at gmail.com
> <mailto:wkatsak at gmail.com>> wrote:
>
> Dave,
>
> Thanks for the reply. I should have made it clearer that I am not
> running this on a Netgear 3800, I am running the sqm system on an
> Atom D510 box at 1.66 GHz (two cores + hyperthreads) with 2 GB RAM
> and good Intel NICs. While running the rrul, the CPU is barely
> breaking a sweat.
>
> The OS is Ubuntu server and I've made a nice wrapper to run
> simple.qos via the if-pre-up/post-down hooks.
>
> Can you suggest any tweaks to the settings that would better take
> advantage of the extra CPU that I have?
>
> Thanks,
> Bill
>
>
>
>
> On 03/05/2015 10:43 AM, Dave Taht wrote:
>
> well, cerowrt's inbound shaper runs out of cpu at +60mbits. That is
> possibly part of your problem.
>
> the peaks you are seeing are not bad - but to me, probably
> indicative
> of running out of cpu, which will among other things, drop packets
> burstily.
>
> As comcast has rolled out 100mbit+ service in a ton of places
> (including my home), we really, really, really need to find a way to
> do better rate shaping at higher speeds (or develop a faster
> policer)
> on some successor hardware.
>
> If you turn off inbound shaping (0 for that parameter) my
> measurements
> typically show over 600ms of latency on inbound on comcast at
> 100mbit
> down, but at least, doing the tcp_upload tests, we can hold the
> upload
> more under control. It is a totally unsatisfactory thing to have
> downloads got so much out of control, it really messes up other
> things, inside of a few seconds, on big downloads, but at this
> point I
> have to recommend turning off inbound shaping and just living
> with it.
>
> Very high on my list now is finally writing (or tom sawyering
> someone
> into writing!) "bobbie - the kinder, gentler policer" in the
> hope that
> that could actually run faster and better than shaping does on this
> low end hardware.
>
>
>
> On Thu, Mar 5, 2015 at 7:35 AM, William Katsak
> <wkatsak at gmail.com <mailto:wkatsak at gmail.com>> wrote:
>
> Hello all,
>
> I just moved and had to switch my ISP from Optimum
> (Cablevision) to Comcast
> (100/10 link).
>
> I am running my own port of simple.qos over to
> Debian/Ubuntu, and it worked
> fine on Cablevision (I basically use scripts in if-pre-up.d and
> if-post-down.d to set the variables set up/tear down
> simple.qos).
>
> However, since I moved over to Comcast, I am seeing
> something like 600 ms of
> uplink buffering according to Netlyzer. Also, the Internet
> browsing "feels"
> slow when Netflix is in use elsewhere in the apartment (like
> before I knew
> anything about bufferbloat).
>
> My config looks like this:
> UPLINK=7500
> DOWNLINK=85000
> QDISC=fq_codel
> LLAM="tc_stab"
> LINKLAYER="none"
> OVERHEAD=0
> STAB_MTU=2047
> STAB_MPU=0
> STAB_TSIZE=512
> AUTOFLOW=0
> LIMIT=1001 # sane global default for *LIMIT for fq_codel
> on a small memory
> device
> ILIMIT=
> ELIMIT=
> ITARGET="auto"
> ETARGET="auto"
> IECN="ECN"
> EECN="NOECN"
> SQUASH_DSCP="1"
> SQUASH_INGRESS="0"
> IQDISC_OPTS=""
> EQDISC_OPTS=""
> TC=`which tc`
> #TC="sqm_logger tc"# this redirects all tc calls into the log
> IP=$( which ip )
> INSMOD=`which modprobe`
> TARGET="5ms"
> IPT_MASK="0xff"
> IPT_MASK_STRING="/${IPT_MASK}" # for set-mark
>
> I've also attached the output of a run of rrul against
> netperf.bufferbloat.net <http://netperf.bufferbloat.net>.
>
> Any insight?
>
> Thanks,
> Bill
>
>
> --
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> William Katsak <wkatsak at gmail.com <mailto:wkatsak at gmail.com>>
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--
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