Very relevant comment from Jamie:
> one thing we need to be careful about with texture cache changes is that the X position can be important to whether uploads can be DMAd or not. If we try to squeeze more thin items in horizontally we might hit a slow path during uploads on some platforms I think we might already get this wrong on Mac: https://bugzilla.mozilla.org/show_bug.cgi?id=1603783#c2
Means we'll have a hard time habing both nicely packed atlas allocation schemes and fast uploads, unless we decouple the upload from the packing by uploading conservatively aligned data and then issuing GPU-side copies into a tightly packed shared cache.
Bug 1616901 Comment 6 Edit History
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Very relevant comment from Jamie:
> one thing we need to be careful about with texture cache changes is that the X position can be important to whether uploads can be DMAd or not. If we try to squeeze more thin items in horizontally we might hit a slow path during uploads on some platforms I think we might already get this wrong on Mac: https://bugzilla.mozilla.org/show_bug.cgi?id=1603783#c2
Means we'll have a hard time having both nicely packed atlas allocation schemes and fast uploads, unless we decouple the upload from the packing by uploading conservatively aligned data and then issuing GPU-side copies into a tightly packed shared cache.