[tentacleuno]

I really wonder how much these changes, especially seeing the numbers (4%, 5%), add up at scale. For example, from reading a comment on Hacker News[0], I'm told that small changes can save companies millions and millions on servers. It saves power, too.

[0]: https://news.ycombinator.com/item?id=30461201

[gameswithgo]

Most of these changes speed up the rust compiler rather than how fast the compiled code runs, but in some cases the changes do both. In general, often the total improvement is less than the sum of it's parts, because of diminishing returns. Sometimes though the total savings is MORE than the sum of it's parts. An interesting example I recall from C# work is when one develop made an improvement to the JIT which reduced the number of instructions in List.Add, this made an insignificant improvement in runtime. Another develop also tweaed the List.Add function directly, reducing the number of instructions as well, and again another insignificant improvement in run time. When put together though, the function became small enough to get inlined, which lead to a big improvement in runtime. As well as avoiding the memory hop, sometimes inlining lets the compiler find other optimizations.

[the8472]

Those are mostly compiler speedups, fewer compiled-code speedups. Since most code is executed more often than it is compiled the fleet-level savings will be much smaller. It helps with CI jobs and developer-cycles though.

[OJFord]

Both threads are discussing compiler speedups.