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Wed, 29 Oct 2025 11:45:51 -0700 (PDT) Message-ID: Date: Wed, 29 Oct 2025 19:45:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH V3 6/7] mm/slab: save memory by allocating slabobj_ext array from leftover To: Harry Yoo , akpm@linux-foundation.org, vbabka@suse.cz Cc: andreyknvl@gmail.com, cl@linux.com, dvyukov@google.com, glider@google.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@kernel.org, muchun.song@linux.dev, rientjes@google.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, surenb@google.com, vincenzo.frascino@arm.com, yeoreum.yun@arm.com, tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251027122847.320924-1-harry.yoo@oracle.com> <20251027122847.320924-7-harry.yoo@oracle.com> Content-Language: en-US From: Andrey Ryabinin In-Reply-To: <20251027122847.320924-7-harry.yoo@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 83B0A180006 X-Stat-Signature: e3hzwaqendxoh3znby8ae4m6ogks536y X-Rspam-User: X-HE-Tag: 1761763560-662638 X-HE-Meta: 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 GXJgXs+S 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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 10/27/25 1:28 PM, Harry Yoo wrote: > > +#ifdef CONFIG_SLAB_OBJ_EXT > + > +/* > + * Check if memory cgroup or memory allocation profiling is enabled. > + * If enabled, SLUB tries to reduce memory overhead of accounting > + * slab objects. If neither is enabled when this function is called, > + * the optimization is simply skipped to avoid affecting caches that do not > + * need slabobj_ext metadata. > + * > + * However, this may disable optimization when memory cgroup or memory > + * allocation profiling is used, but slabs are created too early > + * even before those subsystems are initialized. > + */ > +static inline bool need_slab_obj_exts(struct kmem_cache *s) > +{ > + if (!mem_cgroup_disabled() && (s->flags & SLAB_ACCOUNT)) Shouldn't this be !memcg_kmem_online() check? In case of disabled kmem accounting via 'cgroup.memory=nokmem' > + return true; > + > + if (mem_alloc_profiling_enabled()) > + return true; > + > + return false; > +} > +