[pengaru]

In a post-spectre/meltdown world syscalls are a bit more expensive, you'd be hard-pressed to compete with the journal's mmap windows especially for a warm page cache, using pread/pwrite. Especially if you just went naively about it and tried turning every little object access into its own little island of buffered IO. The objects in the journal are quite small, so you'd likely end up having to implement your own page cache/buffer manager in userspace to coalesce the syscalls.

It'd be far more interesting to explore an io_uring based implementation IMNSHO.