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AJvYcCXiVfCMzc6fkK6mx0NG4f9+ShmJRo15Zw9PXsFZoMFg9HDHpRX6eaZkkeVSpct78IOk167MfcGGHoyXjs3AwTFSuac= X-Gm-Message-State: AOJu0YzScSTJiXUvGGlw1Q6kW7QS0tT5urKB808W/gTpYRuf8Qqz1iTF oU4zW57LdbGAF2xua3zC4It44KJFtWH1+Geldgt2vfZ5E+F2Lfpk8w+Pm/GWkp4tbX5TBpRTptZ UpZEgUAmmWBBrCvLcU/31OtUndEHjWE+0ghZl X-Google-Smtp-Source: AGHT+IFv5vpfbKostC5g3aePXzjWYD3i27LtxoUIHoL3ccZDFdBI6HAF5vES5pWsvRQq4hZ0i8kHGMMT6kw5GJg/5U0= X-Received: by 2002:a05:690c:30f:b0:643:ed61:11bb with SMTP id 00721157ae682-658ee791041mr107431767b3.7.1720706120508; Thu, 11 Jul 2024 06:55:20 -0700 (PDT) MIME-Version: 1.0 References: <20240710054336.190410-1-alexs@kernel.org> <20240710054336.190410-2-alexs@kernel.org> <9b1384e7-e75d-4d71-8798-0d47c33cece6@gmail.com> In-Reply-To: <9b1384e7-e75d-4d71-8798-0d47c33cece6@gmail.com> From: Suren Baghdasaryan Date: Thu, 11 Jul 2024 06:55:07 -0700 Message-ID: Subject: Re: [REF PATCH v3 2/2] mm/slab: decouple the SLAB_OBJ_EXT from MEMCG To: Alex Shi Cc: Vlastimil Babka , alexs@kernel.org, Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Randy Dunlap , Yoann Congal , Masahiro Yamada , Petr Mladek Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: DFE671C001A X-Stat-Signature: iars5mrdseq84b5go34g8dmbzwdx381d X-HE-Tag: 1720706121-752951 X-HE-Meta: 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 8Xry/5lm 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 11, 2024 at 4:49=E2=80=AFAM Alex Shi wrote: > > > > On 7/11/24 4:11 PM, Vlastimil Babka wrote: > > On 7/10/24 7:43 AM, alexs@kernel.org wrote: > >> From: "Alex Shi (Tencent)" > >> > >> commit 21c690a349ba ("mm: introduce slabobj_ext to support slab object > >> extensions") selected SLAB_OBJ_EXT on MEMCG just for SLAB_MATCH > >> memcg_data, that included SLAB_OBJ_EXT for MEMCG. In fact, I didn't se= e > >> the necessary to enable SLAB_OBJ_EXT for MEMCG. > >> > >> Let's decouple the SLAB_OBJ_EXT from MEMCG and move out > >> alloc_slab_obj_exts() definition from SLAB_OBJ_EXT only. To alignment > >> the alloc_slab_obj_exts() return 0 for good. change its return value t= o > >> '-1' for always failed with !SLAB_OBJ_EXT. Now we could save unnecessa= ry > >> code from MEMCG but !SLAB_OBJ_EXT. > >> > >> Signed-off-by: Alex Shi (Tencent) > > > > This seems just wrong to me. The memcg hooks for slab do use obj_ext. Y= ou > > made alloc_slab_obj_exts() return -1 and that will just fail all memcg > > charging (unless alloc profiling selects obj_ext). The kernel will appe= ar to > > work, but memcg charging for slab won't happen at all. > > > > So no, it can't be decoupled for slab, only for pages/folios (patch 1). > > Hi Vlastimil, > > Thanks a lot for clarification! Yes, the patch isn't correct. > > Just forgive my stupidity, why the memcg needs SLAB_OBJ_EXT? Because when CONFIG_MEMCG_KMEM=3Dy, slabobj_ext contains obj_cgroup (see: https://elixir.bootlin.com/linux/v6.10-rc7/source/include/linux/memco= ntrol.h#L1593) and that's used for memcg accounting. Look into this call chain: kfree slab_free memcg_slab_free_hook __memcg_slab_free_hook obj_cgroup_uncharge > > And why we need to alloc_slab_obj_exts() at line 3019 with !slab_obj_exts= ? > 3015 for (i =3D 0; i < size; i++) { > 3016 slab =3D virt_to_slab(p[i]); > 3017 > 3018 if (!slab_obj_exts(slab) && > 3019 alloc_slab_obj_exts(slab, s, flags, false)) { > 3020 obj_cgroup_uncharge(objcg, obj_full_size(s))= ; > 3021 continue; > 3022 } > > Thanks! > Alex > > > > > > >> Cc: Randy Dunlap > >> Cc: Yoann Congal > >> Cc: Masahiro Yamada > >> Cc: Petr Mladek > >> --- > >> init/Kconfig | 1 - > >> mm/slab.h | 6 +++--- > >> mm/slub.c | 6 +++--- > >> 3 files changed, 6 insertions(+), 7 deletions(-) > >> > >> diff --git a/init/Kconfig b/init/Kconfig > >> index 26bf8bb0a7ce..61e43ac9fe75 100644 > >> --- a/init/Kconfig > >> +++ b/init/Kconfig > >> @@ -965,7 +965,6 @@ config MEMCG > >> bool "Memory controller" > >> select PAGE_COUNTER > >> select EVENTFD > >> - select SLAB_OBJ_EXT > >> help > >> Provides control over the memory footprint of tasks in a cgroup= . > >> > >> diff --git a/mm/slab.h b/mm/slab.h > >> index 8ffdd4f315f8..6c727ecc1068 100644 > >> --- a/mm/slab.h > >> +++ b/mm/slab.h > >> @@ -559,9 +559,6 @@ static inline struct slabobj_ext *slab_obj_exts(st= ruct slab *slab) > >> return (struct slabobj_ext *)(obj_exts & ~OBJEXTS_FLAGS_MASK); > >> } > >> > >> -int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, > >> - gfp_t gfp, bool new_slab); > >> - > >> #else /* CONFIG_SLAB_OBJ_EXT */ > >> > >> static inline struct slabobj_ext *slab_obj_exts(struct slab *slab) > >> @@ -571,6 +568,9 @@ static inline struct slabobj_ext *slab_obj_exts(st= ruct slab *slab) > >> > >> #endif /* CONFIG_SLAB_OBJ_EXT */ > >> > >> +int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, > >> + gfp_t gfp, bool new_slab); > >> + > >> static inline enum node_stat_item cache_vmstat_idx(struct kmem_cache = *s) > >> { > >> return (s->flags & SLAB_RECLAIM_ACCOUNT) ? > >> diff --git a/mm/slub.c b/mm/slub.c > >> index cc11f3869cc6..f531c2d67238 100644 > >> --- a/mm/slub.c > >> +++ b/mm/slub.c > >> @@ -2075,10 +2075,10 @@ alloc_tagging_slab_free_hook(struct kmem_cache= *s, struct slab *slab, void **p, > >> > >> #else /* CONFIG_SLAB_OBJ_EXT */ > >> > >> -static int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *= s, > >> - gfp_t gfp, bool new_slab) > >> +int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, > >> + gfp_t gfp, bool new_slab) > >> { > >> - return 0; > >> + return -1; > >> } > >> > >> static inline void free_slab_obj_exts(struct slab *slab) > >