CoDel - How to use

Nullity

The test button within pfsense>system>patches.

So this is not a directly applicable patch to an installed pfsense which is what I needed to know.

Thanks.

Yeah, the patch applies to the source-code. See https://forum.pfsense.org/index.php?topic=76132.0 to get accessto the source-code.

Please be careful. That patch was posted by me and it is completely untested. There are a few other incorrect values I later found, but this bug is not vital so I neglected to create a new (and very possibly wrong) patch. If I remember correctly, all the values needing correction were in ~/patches/stable/10/altq_codel.diff and can found rather simply with grep.

I will leave this to the professionals to patch, until I have some experience building pfSense. I wish pfSense's source-code was more accessible. Already I have had to resort to using doktornotor's "illegitmate" pfsense-tools repository on github to refer to code that the unwashed masses can see.

mcwtim

Thanks for the clarification and warning. I tried using Codel with a very functional PRIQ with limiter setup this past weekend at a 50+ person LAN party and Codel seemed to inflict a lot of latency (erratic 200+ ms). Disabled it and we went back to our normal 20-50 ms pings to external game servers.

At home the results seemed to be erratic with a single user and Codel only (different pfSense box). Ended up switching to Barrier Breaker and their SQM fq_codel setup which does actually work very well. Took buffer bloat rating from continuous B-C to a repeatable A+.

Harvy66

I wonder if FairQueue in PFSense could be an option for child disciplines also. fq_CoDel, why are you so close yet so far?!

dtaht

the docsis 3.1 standard is a "16ms" target for pie. Pie interpret's target a bit differently than codel. pie is target 20ms in the linux code and pretty different from the docsis-pie version.

the "target" for codel is what it aims for for local queue delay, while trying to keep the pipe filled. The important part is "keeping the pipe filled". It is certainly feasible to achieve a given queue delay while having terrible throughput (tcp's timing out, and so on).

we hit the issue (needing to increase target) with sub 2.5Mbit uplinks after publication of the codel paper.

Codel by itself is very gentle, it gradually reduces queue length to more reasonable amounts and certainly you can briefly see latencies go to 100s, of ms. even thousands of ms on unresponsive traffic.

fair queuing + codel takes most of the latencies for gamer-ish traffic out of the equation, while still moderating (typically tcp) queue length.

I am sorry you are having such difficulty with the fairq + codel emulation in pfsense. testing for codel's correct behavior is somewhat straightforward using things like the tcp_upload test in the flent suite, or merely saturating the link and looking for time of first drop, 2nd drop, etc to follow the 1/sqrt(100) rule. To make your life more difficult, there are several mildly different versions of codel out there and I have not reviewed the one in pfsense.

We tried all sorts of fairq+aqm combining techniques for several years, before incorporating them into one qdisc. two separate modules have flaws - including being difficult to debug.

Another poster here mentioned they had ping packet loss when using codel. Yes, that will happen. Gotta drop packets, some will be pings. hfsc does some clever priorization so pings more rarely drop - but which would you rather drop, pings? or data?

Harvy66

I would rather see what my queue is seeing. So HFSC does mess with the order in which packets are sent within a queue? I was under the impression that HFSC is only a scheduler and only messes with inter-queue ordering, not intra-queue ordering. So if you select a dumb FIFO child queue, will HFSC change the order in which packets from that queue leave the interface? I know fq_codel and any fair queuing AQM will do that.

Nullity

@Harvy66:

I would rather see what my queue is seeing. So HFSC does mess with the order in which packets are sent within a queue? I was under the impression that HFSC is only a scheduler and only messes with inter-queue ordering, not intra-queue ordering. So if you select a dumb FIFO child queue, will HFSC change the order in which packets from that queue leave the interface? I know fq_codel and any fair queuing AQM will do that.

You are seeing what your flow's queue is seeing, which is all that really matters (End-to-End principle).

If you want to know the details of HFSC, read the paper. It is super-fun and the ladies love an HFSC-man.

gazoo

Forgive me if some of this has been repeated already. I just wanted throw in some input on this. I was playing around with CODELQ last night.
Some observations:
I was using the speedtest.net test which tests for bufferbloat.
My link typically achieves 86x5.6Mbps pretty consistently on off peak hours.
I actually used the bandwidth window to get some settings tweak. Initially I had set the bandwidths to 10% below what my actual speeds were but it cutoff WAY too much of my top end bandwidth. When I did that I was getting an A rating on buffer bloat in both directions but speeds were cut to 75x4.2Mbps
I finally settled by testing on going higher. It was a balancing act because if I went too high then the bufferbloat was bad again as originally seen. If I went too low, it would knock off too much off the limits of the speeds.

So for the download (LAN) queue, I went for 87.5Mbps and was able to download 83-84Mbps.
For the upload (WAN) queue, I went for 6.1Mbps and was able to achieve 5.2 Mbps.
Both these settings resulted in a "B" rating with approximately 60ms of delay.
Considering the upload delay had been 512ms at one point, I say not bad to giving up ~7% of my top end upload bandwidth, ~3% download bandwidth.
I didn't have too much buffer bloat on my download (LAN) because I guess the ISP managed it very well. I believe it was originally at about 100ms

So this whole thing was trial and error but I consistently get the same results which leads me to believe I have achieved the intended goal.

I'm using 2.2.2 4G embedded on a Firebox.

Thanks.

Harvy66

Yeah, the whole point of managing bufferbloat is your firewall needs to be the chokepoint, and if your internet connection's rate varies too much, you can get bloat spikes.

My limited understanding of the bufferbloat problem and some technologies is DOCSIS and DSL don't use native Ethernet which cause them to do some strange batching or fragmenting of your packets. This reduces the efficiently and makes for strange bursts in speeds. The bufferbloat forumns are constantly discussing how to properly emulate how DSL and DOCSIS work in an attempt to artificially create the same bottlenecks in the firewall, which allows better management of bufferbloat.

All of that being said, you need to set your bandwidth to be less than your peak, and losing some bandwidth is part of the cost of getting rid of bufferbloat when your ISP doesn't manage it for you.

Personally, I have a 100Mb connection and have my rates set to 99Mb and I get 1ms of bloat on average. But I seem to be a special case.

tuffcalc

Gazoo - I noticed this too. If I put my full speed in pfsense it is as-if it lowers this amount so it is somewhat less (95%?) of the connection speed you enter for traffic shaping limit.

Harvy66

95% is pretty decent. I see closer to about 97%.

tuffcalc

@Harvy66:

95% is pretty decent. I see closer to about 97%.

Might be 97%, haven't looked in a while. In any event looks like the pfsense coders deliberately lower the speed you enter. Can anyone confirm?

Nullity

I have turned to the dark-side and chose full bandwidth over best latency on my incoming traffic. The average latency increases to ~70ms (~10ms idle) during a link saturating download, but even with artificial throughput limiting I was reaching ~40ms. Addiction to throughput probably stems from years of dial-up… the experience still haunts me. :)

The difference on uploads is huge though; ~600ms vs ~50ms.

My ISP is the not-so-great-but-improving Windstream. I have wondered what other people experience on other ISPs and CPE.

Harvy66

Since I use HFSC even for download traffic shaping, I can make sure Netflix/Youtube buffering is kept to a minimum. I pretty much can't tell the difference, even when using P2P and saturating the downstream.

I have 100Mb with a 2:1 ratio between Normal:Low. P2P will be sitting around 97Mb, then I start of Netflix and I pretty much immediately see P2P drop down to ~32Mb/s and Netflix pushes through ~64Mb/s. Even with DSLReports, I still see an A/A+ during the download test. But if P2P is using 0 and DSLReports is using max, and suddenly P2P jumps up to 33, the bufferbloat can get bad, like C/D, but that's because available bandwidth is decreasing instead of increasing and I'm still stuck with regular CoDel and not fq_CoDel.

Nullity

CoDel's default "target/interval" values should be fixed in 2.2.3. Dave mentioned earlier that the "target" is pretty good at dynamically adjusting, so the fix probably has little effect in that area.

The "interval" is more vital and is noted in the IETF draft as being the only parameter that is required for CoDel to to function, so perhaps changing from a value of 5ms to a more optimal value of 100ms will improve our CoDel experience. :)

Disappointingly, I tried loading up a CODELQ queue in 2.2.3, and I still got the old values… Either the install needs to be fresh or my patch is shit and needs more work. See if it is fixed on any of your 2.2.3 setups.

Harvy66

I wonder how it'll affect my bufferbloat. Right now I have about 1ms, but it can burst quite high given enough TCP streams growing at the same time.

kieranc

@Nullity:

CoDel's default "target/interval" values should be fixed in 2.2.3. Dave mentioned earlier that the "target" is pretty good at dynamically adjusting, so the fix probably has little effect in that area.

The "interval" is more vital and is noted in the IETF draft as being the only parameter that is required for CoDel to to function, so perhaps changing from a value of 5ms to a more optimal value of 100ms will improve our CoDel experience. :)

Disappointingly, I tried loading up a CODELQ queue in 2.2.3, and I still got the old values… Either the install needs to be fresh or my patch is shit and needs more work. See if it is fixed on any of your 2.2.3 setups.

I did a fresh install of 2.2.3 and the target/interval are still inverted.

[2.2.3-RELEASE][admin@pfSense.localdomain]/root: pfctl -vs queue | grep -i codel
altq on em0 codel( target 50 interval 5) bandwidth 600Kb tbrsize 1500 
altq on em1 codel( target 50 interval 5) bandwidth 6Mb tbrsize 6000

Nullity

@kieranc:

@Nullity:

CoDel's default "target/interval" values should be fixed in 2.2.3. Dave mentioned earlier that the "target" is pretty good at dynamically adjusting, so the fix probably has little effect in that area.

The "interval" is more vital and is noted in the IETF draft as being the only parameter that is required for CoDel to to function, so perhaps changing from a value of 5ms to a more optimal value of 100ms will improve our CoDel experience. :)

Disappointingly, I tried loading up a CODELQ queue in 2.2.3, and I still got the old values… Either the install needs to be fresh or my patch is shit and needs more work. See if it is fixed on any of your 2.2.3 setups.

I did a fresh install of 2.2.3 and the target/interval are still inverted.
[2.2.3-RELEASE][admin@pfSense.localdomain]/root: pfctl -vs queue | grep -i codel
altq on em0 codel( target 50 interval 5) bandwidth 600Kb tbrsize 1500 
altq on em1 codel( target 50 interval 5) bandwidth 6Mb tbrsize 6000 

Fudge…

Thank you for letting me know. I will get them to revert my commits.

How can a little fix be so illusive?

Why must you be so confusing, pfSense-tools!?

kieranc

@Nullity:

@kieranc:
@Nullity:

CoDel's default "target/interval" values should be fixed in 2.2.3. Dave mentioned earlier that the "target" is pretty good at dynamically adjusting, so the fix probably has little effect in that area.

The "interval" is more vital and is noted in the IETF draft as being the only parameter that is required for CoDel to to function, so perhaps changing from a value of 5ms to a more optimal value of 100ms will improve our CoDel experience. :)

Disappointingly, I tried loading up a CODELQ queue in 2.2.3, and I still got the old values… Either the install needs to be fresh or my patch is shit and needs more work. See if it is fixed on any of your 2.2.3 setups.

I did a fresh install of 2.2.3 and the target/interval are still inverted.
[2.2.3-RELEASE][admin@pfSense.localdomain]/root: pfctl -vs queue | grep -i codel
altq on em0 codel( target 50 interval 5) bandwidth 600Kb tbrsize 1500 
altq on em1 codel( target 50 interval 5) bandwidth 6Mb tbrsize 6000 
Fudge…

Thank you for letting me know. I will get them to revert my commits.

How can a little fix be so illusive?

Why must you be so confusing, pfSense-tools!?

It looks like you're doing it right but the patch hasn't been merged. I've created a pull request on github to do the same thing, let's see what happens

Do you know why the current codel_alloc(100, 5, 0) results in values of target 50 interval 5? target 5 interval 50 would be better but I dunno where the value of 50 is coming from.

doktornotor

Was never fixed AFAICT? https://redmine.pfsense.org/issues/4692

kieranc

@doktornotor:

Was never fixed AFAICT? https://redmine.pfsense.org/issues/4692

Indeed, has anyone tried the patch? I don't really want to have to build pfsense in order to test it, that's a lot of repos to clone…

edit: PR has been merged, new values should be applied in 2.2.4 or anything built from here on...