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mducharme
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FastTrack slow performance

Mon Sep 03, 2018 5:29 am

Hello,

Sometime in the past few years my home router (hAP AC) has gone from having very fast performance with fasttrack (~6.39 or 6.40) to very slow performance (6.42 is much faster without fasttrack). The issue causes me to get 20Mbps maximum download on an ISP speed test on my wired PC, whereas I continually get 160Mbps download with fasttrack disabled (the CPU is not anywhere near maxed out at the time, only 10%). Re-running the speed test results in a consistent result depending on whether fasttrack is on or off (always 20Mbps with fasttrack on, 160Mbps with it off). I had simply disabled fasttrack because it was fast enough without it, but the other day I tried to figure out what was happening.

I reset my router to factory defaults and did not change any settings, and repeated the speed test. The result was 160Mbps (with fasttrack). So, then I became convinced it must have been something with my config. I took a .backup file of this factory default state where I received 160Mbps with fasttrack (so that I could quickly switch back to compare), and then restored my old config .backup that had the fasttrack slow performance issue. Immediately I saw performance of 20Mbps until I turned fasttrack off, and got 160Mbps download again. Then, to verify, I restored the .backup file I had made just 10 or 15 minutes before of the factory default config (with no changes). Strangely, the fasttrack slow performance problem came back with the restored factory default .backup (disabling fasttrack again resulted in 160Mbps throughput). I do not quite understand how that could happen since the .backup was taken when fasttrack was getting the 160Mbps and is simply the default config of the router with no changes.

However, if I reset the router to factory defaults (as opposed to restoring the .backup of the same config), then suddenly fasttrack works again at 160Mbps.

I have opened a ticket with MikroTik because this bizarre behavior has me at a loss for what might be the cause. Has anybody seen any issues like this?

Thanks!
 
mducharme
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Re: FastTrack slow performance

Tue Sep 04, 2018 1:22 am

UPDATE:

I have done substantial testing and have narrowed down how to cause fasttrack give me fast speed (160Mbps) or fasttrack to give me slow speed (20Mbps), at least on my device:

- If I reset to factory configuration, there is a 30% chance fasttrack will start working at full rate, if it works it will continue to work at full rate until the router is rebooted either once or twice
- If the first factory configuration reset fails to get fasttrack working at full rate, then I factory reset and speed test repeatedly until fasttrack begins to work at full rate, it always works by the third factory reset in a row at the latest.
- Once fasttrack is working, it seems to work consistently (repeated speed tests all show full rate) until a reboot of the router
- At this point, there is a 75% chance that rebooting the router (not a single config change made since factory reset) causes fasttrack to develop the slow speed issue again
- If fasttrack is still working at full rate after the first reboot (this happens occasionally), a second reboot will cause fasttrack to develop the slow speed issue again
- Once fasttrack has the slow speed issue again, I can reboot a dozen times and it will not result in fasttrack working at full rate again
- However, I then factory reset the device 1-3 times in a row and by the third time at the latest fasttrack will work again until another reboot or two later.

No config changes whatsoever were made during the testing above from the factory default.

This is on a hAP AC.

Anybody else experience anything like this?
 
jo2jo
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Re: FastTrack slow performance

Wed Sep 05, 2018 5:19 am

ive never experienced anything similar, but it would help to know what is your source of internet and its speed. Have you tried connecting to that directly (use a FW/becareful if its a modem or ISP device that directly gives your PC a public IP).

Have you changed the cat patch cables? (im sure you have , but also be sure the MT link is at gigabit, and check the TX/RX errors and Ethernet errors to rule that out).

Do you have another MT or 2 to run a MT bandwidth test through the problem device (ie no internet just private IPs), better yet use traffic-generator if you are tech/networking/ros savy (otherwise builtin mt bandwidth-test should help).

What does the MT's CPU usage look like when you are doing your internet speed tests?
:beep :beep :beep
 
mducharme
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Re: FastTrack slow performance

Wed Sep 05, 2018 9:14 pm

ive never experienced anything similar, but it would help to know what is your source of internet and its speed. Have you tried connecting to that directly (use a FW/becareful if its a modem or ISP device that directly gives your PC a public IP).
Yes I have and I consistently get the full 160Mbps rate then.
Have you changed the cat patch cables? (im sure you have , but also be sure the MT link is at gigabit, and check the TX/RX errors and Ethernet errors to rule that out).
The link is at gigabit, and no errors.
Do you have another MT or 2 to run a MT bandwidth test through the problem device (ie no internet just private IPs), better yet use traffic-generator if you are tech/networking/ros savy (otherwise builtin mt bandwidth-test should help).
I suppose I could give this a try, I do have another MT handy.
What does the MT's CPU usage look like when you are doing your internet speed tests?
Only around 5-9% usage, except when fasttrack is working properly and giving me full rate, then it hits 160Mbps, and higher CPU usage ~25%.

Here is the thing, when I am having this issue with fasttrack, I have switched off the fasttrack-connection rule, immediately tested again, and got 160Mbps. Turned on the fasttrack connection rule, immediately tested again, got 20Mbps. I repeated this about 20 times in a row to be certain, switching on and off the fasttrack connection rule and retesting the speed. Each time with fasttrack off I got 160Mbps and each time with it on I got 20Mbps. This was all in a 10 minute span. Based on this behavior I do not understand how it could be an issue with anything except fasttrack itself, unless having fasttrack disabled fixes some other unrelated problem somehow.
Last edited by mducharme on Fri Sep 07, 2018 4:36 am, edited 1 time in total.
 
cgrey001
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Re: FastTrack slow performance

Fri Sep 07, 2018 2:30 am

Interesting post. It caught my attention because your slow down is the same rate I'm randomly experience at 20mbps. I have gigabit internet and when things are working well I am able to max out the connection on wired or wireless (RB450Gx4). However, I get random slow downs to 20mbps on a wide range of device. The only difference I noticed which is potentially visible because of my internet speed is my throughput gets cut roughly in half after a few speed test and stays that way. What seems to be a random number of reboots of the router and AP will eventually restore the performance. I will look at my CPU utilization and fast track settings based on what you have experienced.
 
mducharme
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Re: FastTrack slow performance

Tue Sep 11, 2018 7:07 am

Hi,

Just as an update, my issue has apparently been resolved by upgrading the Intel NIC driver in my desktop.

The only possible explanation in my mind is that fasttrack must change the behavior of the router, regarding how it handles TCP, in a very fundamental way (other than simply bypassing additional processing). Otherwise, simply disabling fasttrack should not have worked around the issue.
 
SPKA16
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Re: FastTrack slow performance

Tue Sep 11, 2018 1:25 pm

I also have mixed results with fasttrack on my HAPac - I use it as main router on my home netwerk with a PPPoE WAN port.
Sometimes when rebooting it works and I can get fullspeed internet 500Mbit+ sometimes it doesn't and only have a download speed op 20Mbit but upload is still OK. Then I just disable it and use it without fasttrack to reach ~200Mbit..

It is weird behavior which I didn't pinpoint yet what causes this.
It also seems to have something to do with how fast the system reboots, sometimes it takes a bit longer and then fasttrack doesn't seem to work but I cant confirm this yet.
Yesterday i updated to the latest current update, board rebooted fast, turned fasttrack back on and it works again. Afraid to update firmware now =]

We used fasttrack on more boards and never had this problem. It could be something with the hardware (HAPac) and fasttrack? I always though it had something to do with the PPPoE interface cause fasttrack wasn't even supported on those interfaces in the beginning.
 
mducharme
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Re: FastTrack slow performance

Tue Sep 11, 2018 6:21 pm

We used fasttrack on more boards and never had this problem. It could be something with the hardware (HAPac) and fasttrack? I always though it had something to do with the PPPoE interface cause fasttrack wasn't even supported on those interfaces in the beginning.
I don't use PPPoE on this unit. It has now been working fine with FastTrack since updating the Intel NIC driver to the latest version. However, there must be some different behavior that fasttrack causes that triggers the problem on the NIC with the old driver. Otherwise, disabling fasttrack should not have worked around the performance issue.
 
mkx
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Re: FastTrack slow performance

Tue Sep 11, 2018 9:26 pm

It has now been working fine with FastTrack since updating the Intel NIC driver to the latest version. However, there must be some different behavior that fasttrack causes that triggers the problem on the NIC with the old driver. Otherwise, disabling fasttrack should not have worked around the performance issue.
I'd expect that slight variations in timing of ethernet frame delivery could cause enormous difference in end performance. It could well be that (slightly) misbehaving fasttrack pushes timing to the edge of allowed (or even slightly beyond the edge) then too strict NIC driver might panic.
BR,
Metod
 
mducharme
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Re: FastTrack slow performance

Wed Sep 12, 2018 9:08 am

I'd expect that slight variations in timing of ethernet frame delivery could cause enormous difference in end performance. It could well be that (slightly) misbehaving fasttrack pushes timing to the edge of allowed (or even slightly beyond the edge) then too strict NIC driver might panic.
Yes, that makes a great deal of sense. That would indicate that there might still be some corner-case issue with FastTrack.
 
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Re: FastTrack slow performance

Wed Sep 12, 2018 10:20 am

I lost you there - So you fixed the issue by upgrading driver on other device (endpoint of connection), and still thinking about problems in fasttrack???
Give me a break!

If your device ethernet driver was flawed, it might have issues on RX buffer, and on specific receive frequency had issues to reply in time, or many different reasons.

Only thing that fastpath does it changes RTT ( usefull mostly for TCP) for packets, and reduce CPU load on the device (usefull only when you are hitting 100% load)
With great knowledge comes great responsibility, because of ability to recognize id... incompetent people much faster.
 
mducharme
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Re: FastTrack slow performance

Wed Sep 12, 2018 7:42 pm

I lost you there - So you fixed the issue by upgrading driver on other device (endpoint of connection), and still thinking about problems in fasttrack???
The problem was certainly with the NIC driver. However, I ran dozens of tests where I got full speed when fasttrack was turned off (160Mbps) and turned it on immediately, tested again, got the 20Mbps result. Now, after the driver update, I am correctly getting the full rate with fasttrack on (160Mbps). I now get the same rate with fasttrack on with the new NIC driver as I got with fasttrack off with the old one. I would not have expected FastTrack to have any effect on packet delivery. It seems it does, somehow, otherwise there should not have been a difference, since in both cases, the rate was 160Mbps. It is not necessarily anything that MT needs to fix (or can fix), but it is good to know for troubleshooting for the future.

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