timrowledge
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Pi 4 sudden drastic slowdown by two-thirds

Fri Oct 02, 2020 4:54 pm

I've got a couple of Pi 4/ 4GB which are used pretty much exclusively for runnning Squeak Smalltalk. It runs very nicely normally; about 30% the performance of my big expensive iMac. By the general quick and dirty benchmark we use to keep an eye on performance the Pi 4 scores 810/60.

For some reason the Pi that has a USB3 attached boot SSD has started slowing down drastically - the above benchmark dropping to 320/22. What makes it extra weird is that this is a recent change and not matching the timeline of adding the SSD nor indeed anything else I can work out. About a month ago(?) I noticed it feeling very slow, thested and saw the benchmark collapse. The rest of the Pi seemed sluggish too in a sort of "this doesn't feel right" way. I thought that maybe the SSD had got clogged up and wasn't running TRIM, so I fiddled with that, cleaned up 90+ GB, set the /etc/fstab 'discard' option and things seemed to improve.

More recently though I've seen some odd temperature reading/throttling indications from the menubar cpu temperature widget. That seems to be claiming that the cpu is throttling any time the temp gets to ~32C which seems a bit strange. Is that widget reliable? No idea.
The other Pi is running off a plain old uSD card and is not throttling and has never got hot enough to even hint at it even though it sits there at 36C idling.

Just FYI, the software is identical, as in copied from one to the other yesterday. The screen resolution settings are the same. Both are conencted via VNC (I don't have desk space to have a bunch of separate montiors if I wanted them) over ethernet. So far as I can tell from the info listed by RonR's excellent eeprom manager script they both have identical eeprom versions.

Right now I'm flailing around trying to find any other reports of this kind of behaviour, putting off swapping the two boards as to SSD/uSD becuse it means getting out the hex keys, and hoping that somebody else has seen this and solved it previously.

Haaaalp!
Making Smalltalk on ARM since 1986; making your Scratch better since 2012

ejolson
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Re: Pi 4 sudden drastic slowdown by two-thirds

Fri Oct 02, 2020 5:06 pm

timrowledge wrote:
Fri Oct 02, 2020 4:54 pm
Haaaalp!
How about swapping power supplies? My experience is the Pi also throttles if the voltage drops too low.

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FTrevorGowen
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Re: Pi 4 sudden drastic slowdown by two-thirds

Fri Oct 02, 2020 5:09 pm

Not sure if this might help with the "diagnosis", but are you aware of glances which, at least for me, pointed (in more detail) to the cause of "program stalls" within a python-based task. (It was suggested as a diagnostic tool in another thread quite some time ago which I happened to read through when "modding" at the time). FWIW, there are some comparisons with top or htop reporting can be seen here: https://www.cpmspectrepi.uk/raspberry_p ... sMyPi.html
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, and a A+) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

timrowledge
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Re: Pi 4 sudden drastic slowdown by two-thirds

Fri Oct 02, 2020 8:49 pm

ejolson wrote:
Fri Oct 02, 2020 5:06 pm
timrowledge wrote:
Fri Oct 02, 2020 4:54 pm
Haaaalp!
How about swapping power supplies? My experience is the Pi also throttles if the voltage drops too low.
Yup, that seems to be the one. It seems obvious with hindsight but I had never thought about throttling as anything other than a temperature thing.

It is of course about the last thing one checks, but for the first time ever this morning I actually saw the on-screen 'check your power supply' widget. It was a little more compicated to swap the PSU since my Pi is in a nice case I made with an open-frame PSU inside. Fortunately I had a spare PSU on my desk since I am about to make another case, so an hour with allen keys & screwdrivers and ta-da! Back to 810/60 benchmarks.

I guess some part in the original PSU must have started to fade. It's a couple of years old and has been doing perfectly well (almost) all that time. Maybe I'll put in on a 'scope and see what that tells me.
Making Smalltalk on ARM since 1986; making your Scratch better since 2012

dustnbone
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Re: Pi 4 sudden drastic slowdown by two-thirds

Fri Oct 02, 2020 8:51 pm

It's more likely a bad connection vs a problem with the actual supply in my experience. Micro USB connectors in particular, kinda suck.

timrowledge
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Re: Pi 4 sudden drastic slowdown by two-thirds

Sat Oct 03, 2020 1:23 am

dustnbone wrote:
Fri Oct 02, 2020 8:51 pm
It's more likely a bad connection vs a problem with the actual supply in my experience. Micro USB connectors in particular, kinda suck.
In this case that isn't a problem since the power is supplied through the GPIO connectors from a little board I knocked up. But yes, micro-usb is not ideal really, and the only usb-c unit I have is for my wife's macbook, so I make my own from PSU's like this -
https://www.amazon.ca/dp/B00DECXUD0/ref ... FbC5ZCJSW
Making Smalltalk on ARM since 1986; making your Scratch better since 2012

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jahboater
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Re: Pi 4 sudden drastic slowdown by two-thirds

Sat Oct 03, 2020 1:48 am

timrowledge wrote:
Sat Oct 03, 2020 1:23 am
so I make my own from PSU's like this -
https://www.amazon.ca/dp/B00DECXUD0/ref ... FbC5ZCJSW
The official Pi4 usb-c PSU is much cheaper than that, and is known to be reliable.
Pi4 8GB running PIOS64 Lite

ejolson
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Re: Pi 4 sudden drastic slowdown by two-thirds

Sat Oct 03, 2020 3:14 am

jahboater wrote:
Sat Oct 03, 2020 1:48 am
timrowledge wrote:
Sat Oct 03, 2020 1:23 am
so I make my own from PSU's like this -
https://www.amazon.ca/dp/B00DECXUD0/ref ... FbC5ZCJSW
The official Pi4 usb-c PSU is much cheaper than that, and is known to be reliable.
The exchange rate and duties put the official power supply at about CA$ 20. It is surprising the custom made power supply is not able to deliver enough power. I wonder what will be discovered when the broken supply is connected to a scope.

Do you wire both 5V pins of the GPIO?

timrowledge
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Re: Pi 4 sudden drastic slowdown by two-thirds

Sun Oct 04, 2020 12:43 am

The (probably) failing PSU was a dirt cheap one via AliExpress a couple of years ago that has worked perfectly until quite recently. I think it was C$7 delivered, so really not bad value. It’s a shame that it seems to have failed, but that’s life. I think maybe I just ended up overstretching it it with a Pi 4, SSD, and fan.

The replacement unit is indeed a bit more expensive but
  • it is a bit easier to get stuff from amazon right now
  • it’s a bit more powerful.
Why use one of these instead of an “official RPF” one? Because I wanted to fit the entire stack in a nice box and have a normal mains lead instead of yet another wall wart. I used a dead PC power supply case (a rather nice flashy one) because it seems a nice option, had a nice mains socket/switch, mounting for an 80mm fan, cute slots in the ‘front’ for the air, and plenty of room to fit a Pi, SSD and so on. I have a USB 3 socket and Ethernet next to the mains lead socket, a pair of USB 2 sockets on the front, one HDMI out to the front although I virtually always use VNC, and the audio on the front.
I like how it looks as a finished device and it has functioned just fine until this issue. And with the new PSU al seems well and performance is as expected.
Making Smalltalk on ARM since 1986; making your Scratch better since 2012

pidd
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Re: Pi 4 sudden drastic slowdown by two-thirds

Sun Oct 04, 2020 3:52 am

I'm with you on the wall-wart, especially upside down ones that physically conflict in two-row extension blocks, I'd prefer to have mains leads and have the choice of mains plugs or wiring them in.

dustnbone
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Re: Pi 4 sudden drastic slowdown by two-thirds

Mon Oct 05, 2020 7:50 pm

timrowledge wrote:
Sun Oct 04, 2020 12:43 am
I used a dead PC power supply case (a rather nice flashy one) because it seems a nice option, had a nice mains socket/switch, mounting for an 80mm fan, cute slots in the ‘front’ for the air, and plenty of room to fit a Pi, SSD and so on.
This is brilliant, I like it.

As for the PSU connection to the header pins, I'd double check those too. I've had issues where my pin connectors became sloppy over time and weren't making good contact with the pins, particularly after I accidentaly gave one of them a good tug sideways.

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