D3D11Commands.cpp is doing FName resolutions in the critical fast path. This looks to be a regression from the memory freezing refactor.
Compare editor runtime performance between 4.23 and 4.26 (unsure if this manifests in intermediate versions). 4.26 is slower on the render thread.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-109910 in the post.