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Harding" To: Andrew Morton Cc: "Tobin C. Harding" , Roman Gushchin , Alexander Viro , Christoph Hellwig , Pekka Enberg , David Rientjes , Joonsoo Kim , Christopher Lameter , Matthew Wilcox , Miklos Szeredi , Andreas Dilger , Waiman Long , Tycho Andersen , "Theodore Ts'o" , Andi Kleen , David Chinner , Nick Piggin , Rik van Riel , Hugh Dickins , Jonathan Corbet , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH v3 01/15] slub: Add isolate() and migrate() methods Date: Thu, 11 Apr 2019 11:34:27 +1000 Message-Id: <20190411013441.5415-2-tobin@kernel.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190411013441.5415-1-tobin@kernel.org> References: <20190411013441.5415-1-tobin@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add the two methods needed for moving objects and enable the display of the callbacks via the /sys/kernel/slab interface. Add documentation explaining the use of these methods and the prototypes for slab.h. Add functions to setup the callbacks method for a slab cache. Add empty functions for SLAB/SLOB. The API is generic so it could be theoretically implemented for these allocators as well. Change sysfs 'ctor' field to be 'ops' to contain all the callback operations defined for a slab cache. Display the existing 'ctor' callback in the ops fields contents along with 'isolate' and 'migrate' callbacks. Co-developed-by: Christoph Lameter Signed-off-by: Tobin C. Harding --- include/linux/slab.h | 70 ++++++++++++++++++++++++++++++++++++++++ include/linux/slub_def.h | 3 ++ mm/slub.c | 59 +++++++++++++++++++++++++++++---- 3 files changed, 126 insertions(+), 6 deletions(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index 9449b19c5f10..886fc130334d 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -154,6 +154,76 @@ void memcg_create_kmem_cache(struct mem_cgroup *, struct kmem_cache *); void memcg_deactivate_kmem_caches(struct mem_cgroup *); void memcg_destroy_kmem_caches(struct mem_cgroup *); +/* + * Function prototypes passed to kmem_cache_setup_mobility() to enable + * mobile objects and targeted reclaim in slab caches. + */ + +/** + * typedef kmem_cache_isolate_func - Object migration callback function. + * @s: The cache we are working on. + * @ptr: Pointer to an array of pointers to the objects to isolate. + * @nr: Number of objects in @ptr array. + * + * The purpose of kmem_cache_isolate_func() is to pin each object so that + * they cannot be freed until kmem_cache_migrate_func() has processed + * them. This may be accomplished by increasing the refcount or setting + * a flag. + * + * The object pointer array passed is also passed to + * kmem_cache_migrate_func(). The function may remove objects from the + * array by setting pointers to %NULL. This is useful if we can + * determine that an object is being freed because + * kmem_cache_isolate_func() was called when the subsystem was calling + * kmem_cache_free(). In that case it is not necessary to increase the + * refcount or specially mark the object because the release of the slab + * lock will lead to the immediate freeing of the object. + * + * Context: Called with locks held so that the slab objects cannot be + * freed. We are in an atomic context and no slab operations + * may be performed. + * Return: A pointer that is passed to the migrate function. If any + * objects cannot be touched at this point then the pointer may + * indicate a failure and then the migration function can simply + * remove the references that were already obtained. The private + * data could be used to track the objects that were already pinned. + */ +typedef void *kmem_cache_isolate_func(struct kmem_cache *s, void **ptr, int nr); + +/** + * typedef kmem_cache_migrate_func - Object migration callback function. + * @s: The cache we are working on. + * @ptr: Pointer to an array of pointers to the objects to migrate. + * @nr: Number of objects in @ptr array. + * @node: The NUMA node where the object should be allocated. + * @private: The pointer returned by kmem_cache_isolate_func(). + * + * This function is responsible for migrating objects. Typically, for + * each object in the input array you will want to allocate an new + * object, copy the original object, update any pointers, and free the + * old object. + * + * After this function returns all pointers to the old object should now + * point to the new object. + * + * Context: Called with no locks held and interrupts enabled. Sleeping + * is possible. Any operation may be performed. + */ +typedef void kmem_cache_migrate_func(struct kmem_cache *s, void **ptr, + int nr, int node, void *private); + +/* + * kmem_cache_setup_mobility() is used to setup callbacks for a slab cache. + */ +#ifdef CONFIG_SLUB +void kmem_cache_setup_mobility(struct kmem_cache *, kmem_cache_isolate_func, + kmem_cache_migrate_func); +#else +static inline void +kmem_cache_setup_mobility(struct kmem_cache *s, kmem_cache_isolate_func isolate, + kmem_cache_migrate_func migrate) {} +#endif + /* * Please use this macro to create slab caches. Simply specify the * name of the structure and maybe some flags that are listed above. diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h index d2153789bd9f..2879a2f5f8eb 100644 --- a/include/linux/slub_def.h +++ b/include/linux/slub_def.h @@ -99,6 +99,9 @@ struct kmem_cache { gfp_t allocflags; /* gfp flags to use on each alloc */ int refcount; /* Refcount for slab cache destroy */ void (*ctor)(void *); + kmem_cache_isolate_func *isolate; + kmem_cache_migrate_func *migrate; + unsigned int inuse; /* Offset to metadata */ unsigned int align; /* Alignment */ unsigned int red_left_pad; /* Left redzone padding size */ diff --git a/mm/slub.c b/mm/slub.c index d30ede89f4a6..ae44d640b8c1 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4326,6 +4326,33 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags) return err; } +void kmem_cache_setup_mobility(struct kmem_cache *s, + kmem_cache_isolate_func isolate, + kmem_cache_migrate_func migrate) +{ + /* + * Mobile objects must have a ctor otherwise the object may be + * in an undefined state on allocation. Since the object may + * need to be inspected by the migration function at any time + * after allocation we must ensure that the object always has a + * defined state. + */ + if (!s->ctor) { + pr_err("%s: require constructor to setup mobility\n", s->name); + return; + } + + s->isolate = isolate; + s->migrate = migrate; + + /* + * Sadly serialization requirements currently mean that we have + * to disable fast cmpxchg based processing. + */ + s->flags &= ~__CMPXCHG_DOUBLE; +} +EXPORT_SYMBOL(kmem_cache_setup_mobility); + void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, unsigned long caller) { struct kmem_cache *s; @@ -5010,13 +5037,33 @@ static ssize_t cpu_partial_store(struct kmem_cache *s, const char *buf, } SLAB_ATTR(cpu_partial); -static ssize_t ctor_show(struct kmem_cache *s, char *buf) +static int op_show(char *buf, const char *txt, unsigned long addr) { - if (!s->ctor) - return 0; - return sprintf(buf, "%pS\n", s->ctor); + int x = 0; + + x += sprintf(buf, "%s : ", txt); + x += sprint_symbol(buf + x, addr); + x += sprintf(buf + x, "\n"); + + return x; +} + +static ssize_t ops_show(struct kmem_cache *s, char *buf) +{ + int x = 0; + + if (s->ctor) + x += op_show(buf + x, "ctor", (unsigned long)s->ctor); + + if (s->isolate) + x += op_show(buf + x, "isolate", (unsigned long)s->isolate); + + if (s->migrate) + x += op_show(buf + x, "migrate", (unsigned long)s->migrate); + + return x; } -SLAB_ATTR_RO(ctor); +SLAB_ATTR_RO(ops); static ssize_t aliases_show(struct kmem_cache *s, char *buf) { @@ -5429,7 +5476,7 @@ static struct attribute *slab_attrs[] = { &objects_partial_attr.attr, &partial_attr.attr, &cpu_slabs_attr.attr, - &ctor_attr.attr, + &ops_attr.attr, &aliases_attr.attr, &align_attr.attr, &hwcache_align_attr.attr, -- 2.21.0