Re: SLUB: percpu partial object count is highly inaccurate, causing some memory wastage and maybe also worse tail latencies?

[Christoph Lameter]

On Wed, 13 Jan 2021, Jann Horn wrote:

> Some brainstorming:
>
> Maybe you could have an atomic counter in kmem_cache_cpu that tracks
> the number of empty frozen pages that are associated with a specific
> CPU? So the freeing slowpath would do its cmpxchg_double, and if the


The latencies of these functions are so low that any additional counter
will have significant performance impacts. An atomic counter would be waay
out there.

> You could additionally have a plain percpu counter, not tied to the

The performance critical counters are already all per cpu. I enhanced the
percpu subsystem specifically to support latency critical operations in
the fast path of the slab allocators.