On Thu, Aug 29, 2024 at 10:36:01AM GMT, Muchun Song wrote: > > > > On Aug 29, 2024, at 03:03, Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote: > > > > Hi Muchun, > > > > On Wed, Aug 28, 2024 at 10:36:06AM GMT, Muchun Song wrote: > >> > >> > >>> On Aug 28, 2024, at 01:23, Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote: > >>> > > [...] > >>>> > >>>> Does it handle the case of a too-big-to-be-a-slab-object allocation? > >>>> I think it's better to handle it properly. Also, why return false here? > >>>> > >>> > >>> Yes I will fix the too-big-to-be-a-slab-object allocations. I presume I > >>> should just follow the kfree() hanlding on !folio_test_slab() i.e. that > >>> the given object is the large or too-big-to-be-a-slab-object. > >> > >> Hi Shakeel, > >> > >> If we decide to do this, I suppose you will use memcg_kmem_charge_page > >> to charge big-object. To be consistent, I suggest renaming kmem_cache_charge > >> to memcg_kmem_charge to handle both slab object and big-object. And I saw > >> all the functions related to object charging is moved to memcontrol.c (e.g. > >> __memcg_slab_post_alloc_hook), so maybe we should also do this for > >> memcg_kmem_charge? > >> > > > > If I understand you correctly, you are suggesting to handle the general > > kmem charging and slab's large kmalloc (size > KMALLOC_MAX_CACHE_SIZE) > > together with memcg_kmem_charge(). However that is not possible due to > > slab path updating NR_SLAB_UNRECLAIMABLE_B stats while no updates for > > this stat in the general kmem charging path (__memcg_kmem_charge_page in > > page allocation code path). > > > > Also this general kmem charging path is used by many other users like > > vmalloc, kernel stack and thus we can not just plainly stuck updates to > > NR_SLAB_UNRECLAIMABLE_B in that path. > > Sorry, maybe I am not clear . To make sure we are on the same page, let > me clarify my thought. In your v2, I thought if we can rename > kmem_cache_charge() to memcg_kmem_charge() since kmem_cache_charge() > already has handled both big-slab-object (size > KMALLOC_MAX_CACHE_SIZE) > and small-slab-object cases. You know, we have a function of > memcg_kmem_charge_page() which could be used for charging big-slab-object > but not small-slab-object. So I thought maybe memcg_kmem_charge() is a > good name for it to handle both cases. And if we do this, how about moving > this new function to memcontrol.c since all memcg charging functions are > moved to memcontrol.c instead of slub.c. > Oh you want the core function to be in memcontrol.c. I don't have any strong opinion where the code should exist but I do want the interface to still be kmem_cache_charge() because that is what we are providing to the users which charging slab objects. Yes some of those might be big-slab-objects but that is transparent to the users. Anyways, for now I will go with my current approach but on the followup will explore and discuss with you on which code should exist in which file. I hope that is acceptable to you. thanks, Shakeel
