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Feature Suggestion: Assigning Interrupt affinities

hans_glans

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Another thing many users do to help with latency issues is to assign the gpu driver (and optionally its pcie bridge) to a specific core, like described by Calypto here:


Very briefly, it helps alleviating the stress on core 0.
This is achieved by Microsoft’s Interrupt-Affinity Policy Tool which is tedious.

An integration would be a big time saver.
Note that users with HT/SMT enabled would have to proceed differently.
 

W1zzard

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This has been added to test attached build, please confirm
 

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hans_glans

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Looks great! I chose specific core 4 in my test and had this result:
So it did successfully assign the bridge's affinity but not the gpu itself. I'm not quite sure if that makes a difference in the end.

According to Calypto, the actual gpu affinity must be changed.

There are also users reporting freezing when msi mode is set before affinities. (both using a 1080TI - no such reports on other cards)
Is there a way to first apply affinities, have the driver or system restart and then apply msi mode afterwards?
 
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W1zzard

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So it did successfully assign the bridge's affinity but not the gpu itself. I'm not quite sure if that makes a difference in the end.
Very strange, it should have set the GPU's affinity. I'll test with the Microsoft Tool

Is there a way to first apply affinities, have the driver or system restart and then apply msi mode afterwards?
From what I understand affinities and priorities have no effect until MSI is enabled. This could be placebo? What's your sample size?
 

hans_glans

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It's only 2 users, both with a 1080TI, who reported this issue when setting msi mode before affinities.
 

W1zzard

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Does this build work better? Fixed some bugs in the MSI affinity code
 

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hans_glans

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Yes, this time I picked core 7 and the gpu is assigned properly!
It's great already but I would suggest an optimal scenario:
The pci-bridge was still assigned to core 4 from the previous test. It'd be nice if previous affinities (only of gpu and its pci-bridge) were removed and then both the gpu and it's pci-bridge were assigned to the same specified core(s).
 

W1zzard

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I didn’t touch the bridge, it looks for devices of gpu class, with vendor 10de, with driver by nvidia
 

hans_glans

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Yes, but the corresponding bridge should be assigned to the same core as the gpu.
1623883507804.png

Also, shouldn't this only reach from #0 - #9 for my 10 cores processor?
1623883674663.png
 

W1zzard

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Yes, but the corresponding bridge should be assigned to the same core as the gpu.
No reason imo. The PCIe path has nothing to do with interrupt handling

Also, shouldn't this only reach from #0 - #9 for my 10 cores processor?
Correct, typical off-by-one error. Will fix. Also start at "1" to make it more readable for humans? Task Manager starts at 0 though
 

sewerin0911

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These are the right settings for a 5900X with SMT right?

Thanks for adding HDCP btw.
1623979594686.png
 

hans_glans

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I'm personally not proficient enought to tell with certainty. In my experience you would assign SMT affinities either to every other core (so only the physical cores are ticked) or to the specific core + it's thread. I'm not sure if Spread Across All Processors helps over default. Try Calyptos suggestion for SMT in the guide and maybe someone more versatile can shed some light on it here.

No reason imo. The PCIe path has nothing to do with interrupt handling


Correct, typical off-by-one error. Will fix. Also start at "1" to make it more readable for humans? Task Manager starts at 0 though
Not sure - starting at "1" should be easier for inexperienced users, while it probably confuses everyone who is used to microsofts tool.
 

sewerin0911

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I did it like that but also noticed a small bug here. Core starts at 0 (I have 24 Threads) and ends at 24. Actually it should be 23 :D

Also I set my cores like that without the logical cores.

1625323113167.png
 

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W1zzard

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