On Mon, Aug 15, 2022 at 8:31 AM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > On Mon, Aug 15, 2022 at 06:46:46AM -0700, Yosry Ahmed wrote: > > Yeah I understand this much, what I don't understand is why we charge > > the zswap memory through objcg (thus tying it to memcg kmem charging) > > rather than directly through memcg. > > The charged quantities are smaller than a page, so we have to use the > byte interface. > > The byte interface (objcg) was written for slab originally, hence the > link to the kmem option. But note that CONFIG_MEMCG_KMEM is no longer > a user-visible option, and for all intents and purposes a fixed part > of CONFIG_MEMCG. > > (There is the SLOB quirk. But I'm not sure anybody uses slob, let > alone slob + memcg.) Thanks for the clarification, it makes sense to use the byte interface here for this, and thanks for pointing out that CONFIC_MEMCG_KMEM is not part of CONFIG_MEMCG. One more question :) memcg kmem charging can still be disabled even with !CONFIG_MEMCG_KMEM, right? In this case zswap charging will also be off, which seems like an unintended side effect, right?
