I edited my comment. Current glibc will dynamically choose buffer sizes up to 1MB of dirent structures depending on reported st_blksize. No idea when it started doing that, so it might well be it does better now.
I'm sure there are circumstances where a 5x speedup will matter, but most of the time where people use "ls" it's interactively on the command line and it's just not been my experience that it matters in the circumstances where I've had to help people with this. It's more of a "we're right in the middle of something and can't get any results back" kind of situation. I'd say 9 out of 10 times I've had people bring up an issue like this it's because they're uncomfortable with "find" and are trying to get a list of files to do something with that they could easily do directly with "find" and/or where "ls -f" is more than sufficient.
I'm sure there are circumstances where a 5x speedup will matter, but most of the time where people use "ls" it's interactively on the command line and it's just not been my experience that it matters in the circumstances where I've had to help people with this. It's more of a "we're right in the middle of something and can't get any results back" kind of situation. I'd say 9 out of 10 times I've had people bring up an issue like this it's because they're uncomfortable with "find" and are trying to get a list of files to do something with that they could easily do directly with "find" and/or where "ls -f" is more than sufficient.
But as you say, YMMV.