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b=HYcRZS+IH3NA53qeNR1t7lz4cXGIw4wPZytndllh1xX6BjFxk9xVu4MPj/0y0gppx gBxQ6+IiDvZN/iylabx+QlIM1/ycdY/WT4U+cs2pvu0qxXkh04JeCdNOlPT4rTFtvc SgawymG4EUTOYuvcf9jvhDQx7pjxknUspHVXufIEsWImiPvkEXCt4zpTy/O8q0IVnz JVcRHdr26gEy40ao3MlF7s0vI/8uElGcFnpatYKBtsA9bhFT/QC3zBXlBNNrGoU54m N0iVrfinCnOX/CtJhnjbQST0TIBgxySs5zENnP5qZCIg55WwEOo5S96fxE3o46Z07K pcDv353D0v5NQ== From: "Vlastimil Babka (SUSE)" Date: Thu, 05 Nov 2026 09:43:52 +0100 Subject: [PATCH v3 03/10] mm, slab: refactor slab_min/max_order handling X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261105-slub_tiny_rework-v3-3-0484ce59eabb@kernel.org> References: <20261105-slub_tiny_rework-v3-0-0484ce59eabb@kernel.org> In-Reply-To: <20261105-slub_tiny_rework-v3-0-0484ce59eabb@kernel.org> To: Harry Yoo , Andrey Ryabinin Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Geert Uytterhoeven , Conor Dooley , Damien Le Moal , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , kasan-dev@googlegroups.com, "Vlastimil Babka (SUSE)" X-Mailer: b4 0.16.0 X-Stat-Signature: 8g37ks569nogwd1grxcwinimm75skizx X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: 7F9B780005 X-HE-Tag: 1793868247-346653 X-HE-Meta: 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 m47GcDlz 2ftTyxbEcC0dvjPycIr0/e5H2Q1KMJMEr0dFUhDOil+QrgV/WYAaTy/NczXoXRFXlyTYP5HXVLEcg57i/K/eeCZML4sJjnLuW5/nUz2EwM7vOu4b7KibGUAWJlZ8d0Y0gJqCD1rGqnrTKqGVMlTCZjl0wkh1+pEannhosPgXZB2wwOv81+gDWzTvEDFHq52w4MssKsMV8B92wRVN9WWB4vD83Iu20XjSSGHhfzxQ4VfvvN64UxR0ILJ/zedeEXFf6V9cffhB8cft06b9M5IXKMwDgrjwdIWIusmf6/ocP+gsyhlU+XFe2lgSL8B7WSxn3/h7j9mhmT2CljnE9jAKPE6HHhJqhAKg7vaROpJM1c0Ic9W8i4xj1WuXLqg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Setting slab_min_order and slab_max_order as boot-time parameters currently has several not so great aspects: - slab_min_order is not checked against MAX_PAGE_ORDER - slab_min_order can raise slab_max_order - processing requires custom callbacks, their execution order depends on the order of boot time parameters specified - upcoming SLUB_TINY changes would be more complicated Instead of custom callbacks, introduce __initdata variables that hold the boot-time parameter values (if given). All inputs are then evaluated deterministically in kmem_cache_init(). slab_min_order is always capped at slab_max_order and cannot raise it. debug_guardpage_minorder() still overrides any given boot time params, but it could be changed if there's a use case. While at it, rename the slub_min/max_order variables and slub_min_objects to have a "slab_" prefix instead, as their values determine the sizing of slabs, and the "slub_" prefix already became deprecated also for the boot-time parameters. Signed-off-by: Vlastimil Babka (SUSE) --- mm/slub.c | 84 ++++++++++++++++++++++++--------------------------------------- 1 file changed, 32 insertions(+), 52 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 45e077c7526c..30714557306d 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -7684,10 +7684,17 @@ EXPORT_SYMBOL(kmem_cache_alloc_bulk_noprof); * and increases the number of allocations possible without having to * take the list_lock. */ -static unsigned int slub_min_order; -static unsigned int slub_max_order = +static unsigned int slab_min_order; +static unsigned int slab_max_order = IS_ENABLED(CONFIG_SLUB_TINY) ? 1 : PAGE_ALLOC_COSTLY_ORDER; -static unsigned int slub_min_objects; +static unsigned int slab_min_objects; + +/* + * Store values set by boot-time parameters, to be evaluated in + * kmem_cache_init(). UINT_MAX means they were not set, as 0 is a valid value. + */ +static unsigned int slab_min_order_param __initdata = UINT_MAX; +static unsigned int slab_max_order_param __initdata = UINT_MAX; /* * Calculate the order of allocation given an slab object size. @@ -7741,7 +7748,7 @@ static inline int calculate_order(unsigned int size) unsigned int max_objects; unsigned int min_order; - min_objects = slub_min_objects; + min_objects = slab_min_objects; if (!min_objects) { /* * Some architectures will only update present cpus when @@ -7758,10 +7765,10 @@ static inline int calculate_order(unsigned int size) min_objects = 4 * (fls(nr_cpus) + 1); } /* min_objects can't be 0 because get_order(0) is undefined */ - max_objects = max(order_objects(slub_max_order, size), 1U); + max_objects = max(order_objects(slab_max_order, size), 1U); min_objects = min(min_objects, max_objects); - min_order = max_t(unsigned int, slub_min_order, + min_order = max_t(unsigned int, slab_min_order, get_order(min_objects * size)); if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE) return get_order(size * MAX_OBJS_PER_PAGE) - 1; @@ -7782,9 +7789,9 @@ static inline int calculate_order(unsigned int size) * long as at least single object fits within slab_max_order. */ for (unsigned int fraction = 16; fraction > 1; fraction /= 2) { - order = calc_slab_order(size, min_order, slub_max_order, + order = calc_slab_order(size, min_order, slab_max_order, fraction); - if (order <= slub_max_order) + if (order <= slab_max_order) return order; } @@ -8355,50 +8362,14 @@ void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab) * Kmalloc subsystem *******************************************************************/ -static int __init setup_slub_min_order(const char *str, const struct kernel_param *kp) -{ - int ret; - - ret = kstrtouint(str, 0, &slub_min_order); - if (ret) - return ret; +core_param(slab_min_order, slab_min_order_param, uint, 0); +core_param(slub_min_order, slab_min_order_param, uint, 0); - if (slub_min_order > slub_max_order) - slub_max_order = slub_min_order; +core_param(slab_max_order, slab_max_order_param, uint, 0); +core_param(slub_max_order, slab_max_order_param, uint, 0); - return 0; -} - -static const struct kernel_param_ops param_ops_slab_min_order __initconst = { - .set = setup_slub_min_order, -}; -__core_param_cb(slab_min_order, ¶m_ops_slab_min_order, &slub_min_order, 0); -__core_param_cb(slub_min_order, ¶m_ops_slab_min_order, &slub_min_order, 0); - -static int __init setup_slub_max_order(const char *str, const struct kernel_param *kp) -{ - int ret; - - ret = kstrtouint(str, 0, &slub_max_order); - if (ret) - return ret; - - slub_max_order = min_t(unsigned int, slub_max_order, MAX_PAGE_ORDER); - - if (slub_min_order > slub_max_order) - slub_min_order = slub_max_order; - - return 0; -} - -static const struct kernel_param_ops param_ops_slab_max_order __initconst = { - .set = setup_slub_max_order, -}; -__core_param_cb(slab_max_order, ¶m_ops_slab_max_order, &slub_max_order, 0); -__core_param_cb(slub_max_order, ¶m_ops_slab_max_order, &slub_max_order, 0); - -core_param(slab_min_objects, slub_min_objects, uint, 0); -core_param(slub_min_objects, slub_min_objects, uint, 0); +core_param(slab_min_objects, slab_min_objects, uint, 0); +core_param(slub_min_objects, slab_min_objects, uint, 0); #ifdef CONFIG_NUMA static int __init setup_slab_strict_numa(const char *str, const struct kernel_param *kp) @@ -8771,8 +8742,17 @@ void __init kmem_cache_init(void) slab_obj_ext_has_codetag_init(); + if (slab_max_order_param <= MAX_PAGE_ORDER) + slab_max_order = slab_max_order_param; + + if (slab_min_order_param <= MAX_PAGE_ORDER) + slab_min_order = slab_min_order_param; + if (debug_guardpage_minorder()) - slub_max_order = 0; + slab_max_order = 0; + + if (slab_min_order > slab_max_order) + slab_min_order = slab_max_order; /* Inform pointer hashing choice about slub debugging state. */ hash_pointers_finalize(__slub_debug_enabled()); @@ -8823,7 +8803,7 @@ void __init kmem_cache_init(void) pr_info("SLUB: HWalign=%d, Order=%u-%u, MinObjects=%u, CPUs=%u, Nodes=%u\n", cache_line_size(), - slub_min_order, slub_max_order, slub_min_objects, + slab_min_order, slab_max_order, slab_min_objects, nr_cpu_ids, nr_node_ids); } -- 2.56.0