> But in a general sense, I understand why he argues for it.
Andrew is not wrong, but he's talking about optimisations with relatively little impact compared to others and is addressing people who already write software that's otherwise optimised. More concretely, keeping data packed tighter and reducing RAM footprint are not the same. The former does help CPU utilisation but doesn't make as big of an impact on the latter as things that are detrimental to the CPU (such as switching from moving collectors to malloc/free).
> Why do you think most cases wouldn't benefit from this?
The context to which "this" is referring to was "Reducing your RAM consumption is not the best approach to reducing your RAM throughput is my point." For data-packing, Andy Kelley style, to reduce the RAM bandwidth, the access patterns must be very regular, such as processing some large data structure in bulk (where prefetching helps). This is something you could see in batch applications (such as compilers), but not in most programs, which are interactive. If your data access patterns are random, packing it more tightly will not significantly reduce your RAM bandwidth.
Andrew is not wrong, but he's talking about optimisations with relatively little impact compared to others and is addressing people who already write software that's otherwise optimised. More concretely, keeping data packed tighter and reducing RAM footprint are not the same. The former does help CPU utilisation but doesn't make as big of an impact on the latter as things that are detrimental to the CPU (such as switching from moving collectors to malloc/free).
> Why do you think most cases wouldn't benefit from this?
The context to which "this" is referring to was "Reducing your RAM consumption is not the best approach to reducing your RAM throughput is my point." For data-packing, Andy Kelley style, to reduce the RAM bandwidth, the access patterns must be very regular, such as processing some large data structure in bulk (where prefetching helps). This is something you could see in batch applications (such as compilers), but not in most programs, which are interactive. If your data access patterns are random, packing it more tightly will not significantly reduce your RAM bandwidth.