Re: New malloc - first preview

[Rich Felker <dalias@libc.org>]

On Thu, Nov 28, 2019 at 04:56:42PM -0500, Rich Felker wrote:
> Work on the new malloc is well underway, and I have a draft version
> now public at:
> 
> https://github.com/richfelker/mallocng-draft
> 
> Some highlights:

And some updates:

Since posting this, I've found and fixed some bugs. One thing I'm
really happy about is that I didn't have to wade through any
application-level memory corruption. Aside from issues from compilers
doing bad things without -ffreestanding, and the MAP_FAILED issue I
never actually hit, all of them were caught as assertion failure
traps. This is very different from my experience developing the old
malloc in musl, and suggests good coverage for consistency checking
which is tied to hardening. (Note: some of the consistency checks are
probably overzealous and unrelated to likely attack vectors, and may
make sense to disable later to improve performance.)

So now, as of:

https://github.com/richfelker/mallocng-draft/commits/afc39b01c82100cbb3f343c6e0ca1bc963e4ce23

it's now working to run (via LD_PRELOAD interposition) firefox, gimp,
inkscape, and a number of less-demanding applications I've tried. I
haven't done any rigorous testing, but at first glance firefox memory
usage "seems" to be more stable, and varies up/down with usage rather
than just going up.

Strategy for creating new groups and how soon to reuse freed memory
probably still has a lot of suboptimal properties, but I think the new
allocator is usable/testable at this point.

Rich