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From: Muchun Song In-Reply-To: Date: Fri, 30 Aug 2024 14:09:57 +0800 Cc: Roman Gushchin , Andrew Morton , Johannes Weiner , Michal Hocko , Vlastimil Babka , David Rientjes , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Eric Dumazet , "David S . Miller" , Jakub Kicinski , Paolo Abeni , Linux Memory Management List , LKML , Meta kernel team , cgroups@vger.kernel.org, netdev Content-Transfer-Encoding: quoted-printable Message-Id: <6088647D-147A-4704-BBA1-8CEDEDAE2885@linux.dev> References: <20240826232908.4076417-1-shakeel.butt@linux.dev> <97F404E9-C3C2-4BD2-9539-C40237E71B2B@linux.dev> To: Shakeel Butt X-Migadu-Flow: FLOW_OUT > On Aug 29, 2024, at 23:49, Shakeel Butt = wrote: >=20 > On Thu, Aug 29, 2024 at 10:36:01AM GMT, Muchun Song wrote: >>=20 >>=20 >>> On Aug 29, 2024, at 03:03, Shakeel Butt = wrote: >>>=20 >>> Hi Muchun, >>>=20 >>> On Wed, Aug 28, 2024 at 10:36:06AM GMT, Muchun Song wrote: >>>>=20 >>>>=20 >>>>> On Aug 28, 2024, at 01:23, Shakeel Butt = wrote: >>>>>=20 >>> [...] >>>>>>=20 >>>>>> 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? >>>>>>=20 >>>>>=20 >>>>> 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. >>>>=20 >>>> Hi Shakeel, >>>>=20 >>>> 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? >>>>=20 >>>=20 >>> 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). >>>=20 >>> 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. >>=20 >> 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. >>=20 >=20 > 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. >=20 > 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. Fine. No problem. Thanks. >=20 > thanks, > Shakeel