Is there any reasons to not use "mmap" to read files?

[Elronnd]

On Sunday, 6 February 2022 at 09:40:48 UTC, rempas wrote:
> I'm planning to make a change to my program to use "mmap" to 
> the contents of a file rather than "fgetc".  This is because I 
> learned that "mmap" can do it faster.  The thing is, are there 
> any problems that can occur when using "mmap"?

Performance is weird, and depends a lot on your access patterns 
and constraints.  Mmap is not universally fast and, I would 
argue, really only makes sense in a few constrained 
circumstances.  I would not switch to mmap just because you heard 
it was faster; only consider switching if you know i/o is a 
bottleneck for your application and know mmap is the solution.

https://db.cs.cmu.edu/papers/2022/cidr2022-p13-crotty.pdf  
recent, good read.