Re: [PATCH/RFC] z3fold: use per-page read/write lock

[Andi Kleen]

Vitaly Wool <vitalywool@xxxxxxxxx> writes:

> Most of z3fold operations are in-page, such as modifying z3fold
> page header or moving z3fold objects within a page. Taking
> per-pool spinlock to protect per-page objects is therefore
> suboptimal, and the idea of having a per-page spinlock (or rwlock)
> has been around for some time. However, adding one directly to the
> z3fold header makes the latter quite big on some systems so that
> it won't fit in a signle chunk.

> +	atomic_t page_lock;

This doesnt make much sense. A standard spinlock is not bigger
than 4 bytes either. Also reinventing locks is usually a bad
idea: they are tricky to get right, you have no debugging support,
hard to analyze, etc.

-Andi