General OpenPOWER Hardware > General Hardware Discussion

2u Blackbird Build with 18 cores?!

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deepblue:
I wanted to give everyone an update on this particular setup, as its been a little over 2 years since I purchased this from RaptorCS.

I have been able to push the server beyond its natural 1-5% utilization, as backups definitely stress the CPU during an xz compression then saving it to a CIFS share. The Blackbird seems to handle the additional power draw just fine, and it operates without complianing about the CPU being a bit toasty (60c-80c on average).

Note: I am only allowing 18 threads during the xz compression as letting all 72 threads run gives you no performance benefit. If anyone has any ideas as to why this is, I would appreciate the knowledge.

Thermals have not really changed since adding the heat sinks to the VFRs with thermal epoxy. In response to this, I have set the max power utilization to 160w via the WebUI side of the BMC. This has seemed to result in very little perf loss and it makes me feel better knowing I wont blow out my VFRs on the Blackbird.

I have updated from Ubuntu 18.04 to 20.04 with a little hassle, as ZFS did not mount properly due to renamed disk paths. I am still rebuilding from bungled backups, so make sure that your backups are solid before doing anything drastic! Other than having to reclaim my Wordpress MySQL DBs from my backups, it was successful migration.

Other than the server being a bit 'lopsided' when it comes to CPU count/Memory, it has been a solid performer for all my personal web services and various linux server-y things. I would not hesistate to purchase another setup like this so I can have some redundancy, but that will have to wait due to costs and availability.

However, I am very excited to see what comes next from RaptorCS and I am closely watching the developments around Kestrel and their SoftBMC project. I will most likely repurpose this for a workstation machine after Raptor releases a board that has their latest and greatest kit, as there are definite reasons (for me) to move once the hardware drops.

ejfluhr:
Nice update...tx!  Do you know if the xz compression uses the in-processor compression accelerator, or does it just run on the cores?

Do you know if WOF (dynamic frequency boosting) is active?   Since you are so power limited, perhaps it is lowering the core frequency when you add more threads than 1 per core?

deepblue:

--- Quote from: ejfluhr on November 12, 2021, 11:42:44 pm ---Nice update...tx!  Do you know if the xz compression uses the in-processor compression accelerator, or does it just run on the cores?

--- End quote ---

It looks like it runs on the cores. I have to be careful with how many threads my xz compression consumes as it bogs down the system after I allocate 1 thread for every core. I also do gzip backups with mysql and that seems to not bother the CPU much with 18 threads.


--- Quote ---Do you know if WOF (dynamic frequency boosting) is active?   Since you are so power limited, perhaps it is lowering the core frequency when you add more threads than 1 per core?

--- End quote ---

I am not sure if it is, but I am assuming so. The only real change that I have made is that I use a developer build of the blackbird firmware, as I needed help with unbricking it after a failed BIOS update. Maybe one of the folks here can determine if its active from the versions below?

BMC Image: 2.7.0-dev-581-g18878e4f6
Server Image: open-power-blackbird-v2.3-rc2-65-g1bd4a042-dirty

I am not sure if setting my max power draw to 160w is helping the situation, but I have upgraded the chassis fans to provide a lot more airflow to the CPU heatsink and VFRs.

MauryG5:
A good way to test the CPU can be to do some compilations and also be able to establish the number of cores or thread to use, I would have done some tests in the tel sense I think ...

ejfluhr:
Re: the xz compression behavior, can you tell if you are memory bandwidth starved?  Lots of cores vs. Blackbird's meager DIMM capacity isn't a very balanced combination. 

BTW, I looked at your awesome graphs up above more carefully and you can see how current & voltage are moving around --> that looks like the processor is indeed dynamically boosting/dropping frequency to manage within it's power limit.

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