[dm-devel] slab-nomerge (was Re: [git pull] device mapper changes for 4.3)

[Christoph Lameter]

On Fri, 4 Sep 2015, Dave Chinner wrote:

> There are generic cases where it hurts, so no justification should
> be needed for those cases...

Inodes and dentries have constructors. These slabs are not mergeable and
will never be because they have cache specific code to be executed on the
object.

> Really, we don't need some stupidly high bar to jump over here -
> whether merging should be allowed can easily be answered with a
> simple question: "Does the slab have a shrinker or does it back a
> mempool?" If the answer is yes then using SLAB_SHRINKER or
> SLAB_MEMPOOL to trigger the no-merge case doesn't need any more
> justification from subsystem maintainers at all.

The slab shrinkers do not use mergeable slab caches.