From bfc03c15bebf5e0028e21ca5fc0fe4a60a6b6681 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Fri, 2 Sep 2022 14:10:57 -0700 Subject: [PATCH] bpf: Remove usage of kmem_cache from bpf_mem_cache. For bpf_mem_cache based hash maps the following stress test: for (i = 1; i <= 512; i <<= 1) for (j = 1; j <= 1 << 18; j <<= 1) fd = bpf_map_create(BPF_MAP_TYPE_HASH, NULL, i, j, 2, 0); creates many kmem_cache-s that are not mergeable in debug kernels and consume unnecessary amount of memory. Turned out bpf_mem_cache's free_list logic does batching well, so usage of kmem_cache for fixes size allocations doesn't bring any performance benefits vs normal kmalloc. Hence get rid of kmem_cache in bpf_mem_cache. That saves memory, speeds up map create/destroy operations, while maintains hash map update/delete performance. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20220902211058.60789-16-alexei.starovoitov@gmail.com --- kernel/bpf/memalloc.c | 50 ++++++++++++++------------------------------------ 1 file changed, 14 insertions(+), 36 deletions(-) diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c index 8895c01..38fbd15 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -91,17 +91,13 @@ struct bpf_mem_cache { */ struct llist_head free_llist_extra; - /* kmem_cache != NULL when bpf_mem_alloc was created for specific - * element size. - */ - struct kmem_cache *kmem_cache; struct irq_work refill_work; struct obj_cgroup *objcg; int unit_size; /* count of objects in free_llist */ int free_cnt; int low_watermark, high_watermark, batch; - bool percpu; + int percpu_size; struct rcu_head rcu; struct llist_head free_by_rcu; @@ -134,8 +130,8 @@ static void *__alloc(struct bpf_mem_cache *c, int node) */ gfp_t flags = GFP_NOWAIT | __GFP_NOWARN | __GFP_ACCOUNT; - if (c->percpu) { - void **obj = kmem_cache_alloc_node(c->kmem_cache, flags, node); + if (c->percpu_size) { + void **obj = kmalloc_node(c->percpu_size, flags, node); void *pptr = __alloc_percpu_gfp(c->unit_size, 8, flags); if (!obj || !pptr) { @@ -147,9 +143,6 @@ static void *__alloc(struct bpf_mem_cache *c, int node) return obj; } - if (c->kmem_cache) - return kmem_cache_alloc_node(c->kmem_cache, flags, node); - return kmalloc_node(c->unit_size, flags, node); } @@ -207,16 +200,13 @@ static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node) static void free_one(struct bpf_mem_cache *c, void *obj) { - if (c->percpu) { + if (c->percpu_size) { free_percpu(((void **)obj)[1]); - kmem_cache_free(c->kmem_cache, obj); + kfree(obj); return; } - if (c->kmem_cache) - kmem_cache_free(c->kmem_cache, obj); - else - kfree(obj); + kfree(obj); } static void __free_rcu(struct rcu_head *head) @@ -356,7 +346,7 @@ static void prefill_mem_cache(struct bpf_mem_cache *c, int cpu) alloc_bulk(c, c->unit_size <= 256 ? 4 : 1, cpu_to_node(cpu)); } -/* When size != 0 create kmem_cache and bpf_mem_cache for each cpu. +/* When size != 0 bpf_mem_cache for each cpu. * This is typical bpf hash map use case when all elements have equal size. * * When size == 0 allocate 11 bpf_mem_cache-s for each cpu, then rely on @@ -368,40 +358,29 @@ int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu) static u16 sizes[NUM_CACHES] = {96, 192, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096}; struct bpf_mem_caches *cc, __percpu *pcc; struct bpf_mem_cache *c, __percpu *pc; - struct kmem_cache *kmem_cache = NULL; struct obj_cgroup *objcg = NULL; - char buf[32]; - int cpu, i, unit_size; + int cpu, i, unit_size, percpu_size = 0; if (size) { pc = __alloc_percpu_gfp(sizeof(*pc), 8, GFP_KERNEL); if (!pc) return -ENOMEM; - if (percpu) { - unit_size = size; + if (percpu) /* room for llist_node and per-cpu pointer */ - size = LLIST_NODE_SZ + sizeof(void *); - } else { + percpu_size = LLIST_NODE_SZ + sizeof(void *); + else size += LLIST_NODE_SZ; /* room for llist_node */ - unit_size = size; - } + unit_size = size; - snprintf(buf, sizeof(buf), "bpf-%u", size); - kmem_cache = kmem_cache_create(buf, size, 8, 0, NULL); - if (!kmem_cache) { - free_percpu(pc); - return -ENOMEM; - } #ifdef CONFIG_MEMCG_KMEM objcg = get_obj_cgroup_from_current(); #endif for_each_possible_cpu(cpu) { c = per_cpu_ptr(pc, cpu); - c->kmem_cache = kmem_cache; c->unit_size = unit_size; c->objcg = objcg; - c->percpu = percpu; + c->percpu_size = percpu_size; prefill_mem_cache(c, cpu); } ma->cache = pc; @@ -461,8 +440,7 @@ void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma) c = per_cpu_ptr(ma->cache, cpu); drain_mem_cache(c); } - /* kmem_cache and memcg are the same across cpus */ - kmem_cache_destroy(c->kmem_cache); + /* objcg is the same across cpus */ if (c->objcg) obj_cgroup_put(c->objcg); /* c->waiting_for_gp list was drained, but __free_rcu might -- 2.7.4