Re: Address space limits

Stefan Monnier <monnier@iro.umontreal.ca> wrote:

On "personal" computers ... there's been work instead on compressing
64bit pointers to fit into 32bit "boxes" (IIUC it's used in some Chrome
versions) ...

Intel pushed this thing called the “x32” ABI into the Linux kernel (and
possibly some other places) some years ago. This was using the AMD64

 
Indeed, but I got the impression that there is a bit of a revival of
interest for pointer compression as the evidence seems to point to RAM
sizes not increasing very much any more on "end user devices".
 
See for instance https://v8.dev/blog/pointer-compression
 
Note also that this is targeted at JavaScript: dynamically typed
languages tend to suffer more from the 64bit bloat because of their
use of "boxing", meaning that pretty much everything (except usually
for strings and arrays of floats, which are special-cased) doubles
in size when the "box" size is changed from 32bit to 64bit.

We've used compressed 32-bit pointers in Java for more than a decade
now. Every object in the Java VM is 8-aligned, so a 32-bit-wide
aligned pointer gets you access to 32G of adressible application
memory.

This is a win, not just for saving storage but improving performance.
Java applications are often memory-bandwidth limited, so memory
efficiency is a pretty good proxy for performance. The less memory you
use, the more customers you can serve.

Andrew.