This is mimalloc vendored for use in our server code. You can upgrade mimalloc by editing VERSION in update-sources.sh and re-running it.

Usage sites in haskell projects look like:

-- See 'preload-mimalloc/README.md'
-- We want this in all server binary executable sections
common preload-mimalloc
    c-sources:       ../preload-mimalloc/mimalloc/src/static.c
    include-dirs:    ../preload-mimalloc/mimalloc/include
    cc-options:      -DMI_MALLOC_OVERRIDE

In #9447 we see overloading the server with large and slow queries results in high memory usage and what looks like a space leak, involving foreign data from libpq.

See that ticket for details, but mimalloc helps (relative to my glibc) by:

• better avoiding fragmentation, resulting in lower overall memory usage (4GB peak 2.8 aftervs.
• eagerly decomitting memory so that OS-reported memory usage is a useful metric (we do the same in the haskell RTS by specifying --disable-delayed-os-memory-return)

We also benefit by standardizing this, rather than relying on users' glibc version, which might vary in behavior, making debugging difficult.

Other implementations such as tcmalloc or jemalloc were not tested but might perform better or be more tunable.

It's most common and simplest to use the dynamic linker to override malloc. This would work in docker containers we ship, but we want all users to have the same (better) behavior out of the box.