Re: [PATCH 1/1] mlock: split the shmlock_user_lock spinlock into per user_struct spinlock

Peter Zijlstra
2012-05-03T19:31:34Z

On Thu, 2012-05-03 at 23:04 +0530, rajman mekaco wrote:
> The user_shm_lock and user_shm_unlock functions use a single global
> spinlock for protecting the user->locked_shm.

Are you very sure its only protecting user state? This changelog doesn't
convince me you've gone through everything and found it good.

> This is an overhead for multiple CPUs calling this code even if they
> are having different user_struct.
>
> Remove the global shmlock_user_lock and introduce and use a new
> spinlock inside of the user_struct structure.

While I don't immediately see anything wrong with it, I doubt its
useful. What workload run with enough users that this makes a difference
one way or another?