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Thu, 23 Oct 2025 13:52:53 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id AMNqHTUz+mjvQQAAD6G6ig (envelope-from ); Thu, 23 Oct 2025 13:52:53 +0000 From: Vlastimil Babka Date: Thu, 23 Oct 2025 15:52:27 +0200 Subject: [PATCH RFC 05/19] slab: add sheaves to most caches MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251023-sheaves-for-all-v1-5-6ffa2c9941c0@suse.cz> References: <20251023-sheaves-for-all-v1-0-6ffa2c9941c0@suse.cz> In-Reply-To: <20251023-sheaves-for-all-v1-0-6ffa2c9941c0@suse.cz> To: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo Cc: Uladzislau Rezki , "Liam R. Howlett" , Suren Baghdasaryan , Sebastian Andrzej Siewior , Alexei Starovoitov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, bpf@vger.kernel.org, kasan-dev@googlegroups.com, Vlastimil Babka X-Mailer: b4 0.14.3 X-Stat-Signature: kqyppiq6w6kztdtk4oqbafzijzfqj1q4 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 84A592000B X-HE-Tag: 1761227619-479387 X-HE-Meta: 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 k5i6a8Gd EQ8O39vNhfNVzrS6R+jNFVQD/HLaUuWlT6x1gjpnhMGR0V9T6mLiAtGowPWhPAx+pa8lt0By+r4ogAHQ+mc22bTIeOlbKl5PUse7yA2lJ737jdKIMwjHceyU43+yp3fmBRG9gjBuYQa6Pg6wb8R0PfNMpNReDmghkav9Zhatky4KULuepclZeF6RQq5E7YzpvIC4mpwmE27qCPo3Aw9g0M2+bcgOJz8PEMS0szuj3tGZBbz8sgNvwcqONDTW7wS5llQQN83392qE3CpyvfbwnJJaz5ZMlb2fOACIb 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: In the first step to replace cpu (partial) slabs with sheaves, enable sheaves for almost all caches. Treat args->sheaf_capacity as a minimum, and calculate sheaf capacity with a formula that roughly follows the formula for number of objects in cpu partial slabs in set_cpu_partial(). This should achieve roughly similar contention on the barn spin lock as there's currently for node list_lock without sheaves, to make benchmarking results comparable. It can be further tuned later. Don't enable sheaves for kmalloc caches yet, as that needs further changes to bootstraping. Signed-off-by: Vlastimil Babka --- include/linux/slab.h | 6 ------ mm/slub.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 47 insertions(+), 10 deletions(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index cf443f064a66..e42aa6a3d202 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -57,9 +57,7 @@ enum _slab_flag_bits { #endif _SLAB_OBJECT_POISON, _SLAB_CMPXCHG_DOUBLE, -#ifdef CONFIG_SLAB_OBJ_EXT _SLAB_NO_OBJ_EXT, -#endif _SLAB_FLAGS_LAST_BIT }; @@ -238,11 +236,7 @@ enum _slab_flag_bits { #define SLAB_TEMPORARY SLAB_RECLAIM_ACCOUNT /* Objects are short-lived */ /* Slab created using create_boot_cache */ -#ifdef CONFIG_SLAB_OBJ_EXT #define SLAB_NO_OBJ_EXT __SLAB_FLAG_BIT(_SLAB_NO_OBJ_EXT) -#else -#define SLAB_NO_OBJ_EXT __SLAB_FLAG_UNUSED -#endif /* * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests. diff --git a/mm/slub.c b/mm/slub.c index f2b2a6180759..a6e58d3708f4 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -7810,6 +7810,48 @@ static void set_cpu_partial(struct kmem_cache *s) #endif } +static unsigned int calculate_sheaf_capacity(struct kmem_cache *s, + struct kmem_cache_args *args) + +{ + unsigned int capacity; + size_t size; + + + if (IS_ENABLED(CONFIG_SLUB_TINY) || s->flags & SLAB_DEBUG_FLAGS) + return 0; + + /* bootstrap caches can't have sheaves for now */ + if (s->flags & SLAB_NO_OBJ_EXT) + return 0; + + /* + * For now we use roughly similar formula (divided by two as there are + * two percpu sheaves) as what was used for percpu partial slabs, which + * should result in similar lock contention (barn or list_lock) + */ + if (s->size >= PAGE_SIZE) + capacity = 4; + else if (s->size >= 1024) + capacity = 12; + else if (s->size >= 256) + capacity = 26; + else + capacity = 60; + + /* Increment capacity to make sheaf exactly a kmalloc size bucket */ + size = struct_size_t(struct slab_sheaf, objects, capacity); + size = kmalloc_size_roundup(size); + capacity = (size - struct_size_t(struct slab_sheaf, objects, 0)) / sizeof(void *); + + /* + * Respect an explicit request for capacity that's typically motivated by + * expected maximum size of kmem_cache_prefill_sheaf() to not end up + * using low-performance oversize sheaves + */ + return max(capacity, args->sheaf_capacity); +} + /* * calculate_sizes() determines the order and the distribution of data within * a slab object. @@ -7944,6 +7986,10 @@ static int calculate_sizes(struct kmem_cache_args *args, struct kmem_cache *s) if (s->flags & SLAB_RECLAIM_ACCOUNT) s->allocflags |= __GFP_RECLAIMABLE; + /* kmalloc caches need extra care to support sheaves */ + if (!is_kmalloc_cache(s)) + s->sheaf_capacity = calculate_sheaf_capacity(s, args); + /* * Determine the number of objects per slab */ @@ -8562,15 +8608,12 @@ int do_kmem_cache_create(struct kmem_cache *s, const char *name, set_cpu_partial(s); - if (args->sheaf_capacity && !IS_ENABLED(CONFIG_SLUB_TINY) - && !(s->flags & SLAB_DEBUG_FLAGS)) { + if (s->sheaf_capacity) { s->cpu_sheaves = alloc_percpu(struct slub_percpu_sheaves); if (!s->cpu_sheaves) { err = -ENOMEM; goto out; } - // TODO: increase capacity to grow slab_sheaf up to next kmalloc size? - s->sheaf_capacity = args->sheaf_capacity; } #ifdef CONFIG_NUMA -- 2.51.1