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4.26 "set scalar parameter value" is slow

Hello…

I have the exactly same scene in 4.25 and migrated to 4.26. In the scene a blueprint spawns static meshes with dynamic material instances and modifies their variables.

Statgroup_renderThreadCommand difference in engine versions is quite noticeable:

UpdateDeferredCachedUniformExpressions in 4.25 is 1.61 to 2.70 ms
UpdateDeferredCachedUniformExpressions in 4.26 is 131 to 276.00ms

The change is in 4.26 since all versions from 4.19 to 4.25 seem to be as expected.

Disabling r.deferUniformExpressionsCaching just brigs up the original cost that is setting dynamic instance material parameter value in BP.
In 4.26 this seems to be nearly 100x times slower than 4.19 - 4.25.

Any idea what’s going on? I’d really appreciate any thoughts.

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