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## Problem Currently, image generation reads delta layers before writing out subsequent image layers, which updates the access time of the delta layers and effectively puts them at the back of the queue for eviction. This is the opposite of what we want, because after a delta layer is covered by a later image layer, it's likely that subsequent reads of latest data will hit the image rather than the delta layer, so the delta layer should be quite a good candidate for eviction. ## Summary of changes `RequestContext` gets a new `ATimeBehavior` field, and a `RequestContextBuilder` helper so that we can optionally add the new field without growing `RequestContext::new` every time we add something like this. Request context is passed into the `record_access` function, and the access time is not updated if `ATimeBehavior::Skip` is set. The compaction background task constructs its request context with this skip policy. Closes: https://github.com/neondatabase/neon/issues/4969