On Thu, Aug 21, 2014 at 05:11:13PM +0900, Joonsoo Kim wrote:
> Because of chicken and egg problem, initializaion of SLAB is really
> complicated. We need to allocate cpu cache through SLAB to make
> the kmem_cache works, but, before initialization of kmem_cache,
> allocation through SLAB is impossible.
>
> On the other hand, SLUB does initialization with more simple way. It
> uses percpu allocator to allocate cpu cache so there is no chicken and
> egg problem.
>
> So, this patch try to use percpu allocator in SLAB. This simplify
> initialization step in SLAB so that we could maintain SLAB code more
> easily.
>
> From my testing, there is no performance difference.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> ---
> include/linux/slab_def.h | 20 +---
> mm/slab.c | 237 +++++++++++++++-------------------------------
> mm/slab.h | 1 -
> 3 files changed, 81 insertions(+), 177 deletions(-)
>
> diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
> index 8235dfb..b869d16 100644
> --- a/include/linux/slab_def.h
> +++ b/include/linux/slab_def.h
> @@ -8,6 +8,8 @@
> */
>
> struct kmem_cache {
> + struct array_cache __percpu *cpu_cache;
> +
> /* 1) Cache tunables. Protected by slab_mutex */
> unsigned int batchcount;
> unsigned int limit;
> @@ -71,23 +73,7 @@ struct kmem_cache {
> struct memcg_cache_params *memcg_params;
> #endif
>
> -/* 6) per-cpu/per-node data, touched during every alloc/free */
> - /*
> - * We put array[] at the end of kmem_cache, because we want to size
> - * this array to nr_cpu_ids slots instead of NR_CPUS
> - * (see kmem_cache_init())
> - * We still use [NR_CPUS] and not [1] or [0] because cache_cache
> - * is statically defined, so we reserve the max number of cpus.
> - *
> - * We also need to guarantee that the list is able to accomodate a
> - * pointer for each node since "nodelists" uses the remainder of
> - * available pointers.
> - */
> - struct kmem_cache_node **node;
> - struct array_cache *array[NR_CPUS + MAX_NUMNODES];
> - /*
> - * Do not add fields after array[]
> - */
> + struct kmem_cache_node *node[MAX_NUMNODES];
> };
>
> #endif /* _LINUX_SLAB_DEF_H */
> diff --git a/mm/slab.c b/mm/slab.c
> index 5927a17..09b060e 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -237,11 +237,10 @@ struct arraycache_init {
> /*
> * Need this for bootstrapping a per node allocator.
> */
> -#define NUM_INIT_LISTS (3 * MAX_NUMNODES)
> +#define NUM_INIT_LISTS (2 * MAX_NUMNODES)
> static struct kmem_cache_node __initdata init_kmem_cache_node[NUM_INIT_LISTS];
> #define CACHE_CACHE 0
> -#define SIZE_AC MAX_NUMNODES
> -#define SIZE_NODE (2 * MAX_NUMNODES)
> +#define SIZE_NODE (MAX_NUMNODES)
>
> static int drain_freelist(struct kmem_cache *cache,
> struct kmem_cache_node *n, int tofree);
> @@ -253,7 +252,6 @@ static void cache_reap(struct work_struct *unused);
>
> static int slab_early_init = 1;
>
> -#define INDEX_AC kmalloc_index(sizeof(struct arraycache_init))
> #define INDEX_NODE kmalloc_index(sizeof(struct kmem_cache_node))
>
> static void kmem_cache_node_init(struct kmem_cache_node *parent)
> @@ -458,9 +456,6 @@ static inline unsigned int obj_to_index(const struct kmem_cache *cache,
> return reciprocal_divide(offset, cache->reciprocal_buffer_size);
> }
>
> -static struct arraycache_init initarray_generic =
> - { {0, BOOT_CPUCACHE_ENTRIES, 1, 0} };
> -
> /* internal cache of cache description objs */
> static struct kmem_cache kmem_cache_boot = {
> .batchcount = 1,
> @@ -476,7 +471,7 @@ static DEFINE_PER_CPU(struct delayed_work, slab_reap_work);
>
> static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
> {
> - return cachep->array[smp_processor_id()];
> + return this_cpu_ptr(cachep->cpu_cache);
> }
>
> static size_t calculate_freelist_size(int nr_objs, size_t align)
> @@ -1096,9 +1091,6 @@ static void cpuup_canceled(long cpu)
> struct alien_cache **alien;
> LIST_HEAD(list);
>
> - /* cpu is dead; no one can alloc from it. */
> - nc = cachep->array[cpu];
> - cachep->array[cpu] = NULL;
> n = get_node(cachep, node);
>
> if (!n)
> @@ -1108,6 +1100,9 @@ static void cpuup_canceled(long cpu)
>
> /* Free limit for this kmem_cache_node */
> n->free_limit -= cachep->batchcount;
> +
> + /* cpu is dead; no one can alloc from it. */
> + nc = per_cpu_ptr(cachep->cpu_cache, cpu);
> if (nc)
> free_block(cachep, nc->entry, nc->avail, node, &list);
>
> @@ -1135,7 +1130,6 @@ static void cpuup_canceled(long cpu)
> }
> free_array_cache:
> slabs_destroy(cachep, &list);
> - kfree(nc);
> }
> /*
> * In the previous loop, all the objects were freed to
> @@ -1172,32 +1166,23 @@ static int cpuup_prepare(long cpu)
> * array caches
> */
> list_for_each_entry(cachep, &slab_caches, list) {
> - struct array_cache *nc;
> struct array_cache *shared = NULL;
> struct alien_cache **alien = NULL;
>
> - nc = alloc_arraycache(node, cachep->limit,
> - cachep->batchcount, GFP_KERNEL);
> - if (!nc)
> - goto bad;
> if (cachep->shared) {
> shared = alloc_arraycache(node,
> cachep->shared * cachep->batchcount,
> 0xbaadf00d, GFP_KERNEL);
> - if (!shared) {
> - kfree(nc);
> + if (!shared)
> goto bad;
> - }
> }
> if (use_alien_caches) {
> alien = alloc_alien_cache(node, cachep->limit, GFP_KERNEL);
> if (!alien) {
> kfree(shared);
> - kfree(nc);
> goto bad;
> }
> }
> - cachep->array[cpu] = nc;
> n = get_node(cachep, node);
> BUG_ON(!n);
>
> @@ -1389,15 +1374,6 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
> }
>
> /*
> - * The memory after the last cpu cache pointer is used for the
> - * the node pointer.
> - */
> -static void setup_node_pointer(struct kmem_cache *cachep)
> -{
> - cachep->node = (struct kmem_cache_node **)&cachep->array[nr_cpu_ids];
> -}
> -
> -/*
> * Initialisation. Called after the page allocator have been initialised and
> * before smp_init().
> */
> @@ -1408,7 +1384,6 @@ void __init kmem_cache_init(void)
> BUILD_BUG_ON(sizeof(((struct page *)NULL)->lru) <
> sizeof(struct rcu_head));
> kmem_cache = &kmem_cache_boot;
> - setup_node_pointer(kmem_cache);
>
> if (num_possible_nodes() == 1)
> use_alien_caches = 0;
> @@ -1416,8 +1391,6 @@ void __init kmem_cache_init(void)
> for (i = 0; i < NUM_INIT_LISTS; i++)
> kmem_cache_node_init(&init_kmem_cache_node[i]);
>
> - set_up_node(kmem_cache, CACHE_CACHE);
> -
> /*
> * Fragmentation resistance on low memory - only use bigger
> * page orders on machines with more than 32MB of memory if
> @@ -1452,49 +1425,22 @@ void __init kmem_cache_init(void)
> * struct kmem_cache size depends on nr_node_ids & nr_cpu_ids
> */
> create_boot_cache(kmem_cache, "kmem_cache",
> - offsetof(struct kmem_cache, array[nr_cpu_ids]) +
> + offsetof(struct kmem_cache, node) +
> nr_node_ids * sizeof(struct kmem_cache_node *),
> SLAB_HWCACHE_ALIGN);
> list_add(&kmem_cache->list, &slab_caches);
> -
> - /* 2+3) create the kmalloc caches */
> + slab_state = PARTIAL;
>
> /*
> - * Initialize the caches that provide memory for the array cache and the
> - * kmem_cache_node structures first. Without this, further allocations will
> - * bug.
> + * Initialize the caches that provide memory for the kmem_cache_node
> + * structures first. Without this, further allocations will bug.
> */
> -
> - kmalloc_caches[INDEX_AC] = create_kmalloc_cache("kmalloc-ac",
> - kmalloc_size(INDEX_AC), ARCH_KMALLOC_FLAGS);
> -
> - if (INDEX_AC != INDEX_NODE)
> - kmalloc_caches[INDEX_NODE] =
> - create_kmalloc_cache("kmalloc-node",
> + kmalloc_caches[INDEX_NODE] = create_kmalloc_cache("kmalloc-node",
> kmalloc_size(INDEX_NODE), ARCH_KMALLOC_FLAGS);
> + slab_state = PARTIAL_NODE;
>
> slab_early_init = 0;
>
> - /* 4) Replace the bootstrap head arrays */
> - {
> - struct array_cache *ptr;
> -
> - ptr = kmalloc(sizeof(struct arraycache_init), GFP_NOWAIT);
> -
> - memcpy(ptr, cpu_cache_get(kmem_cache),
> - sizeof(struct arraycache_init));
> -
> - kmem_cache->array[smp_processor_id()] = ptr;
> -
> - ptr = kmalloc(sizeof(struct arraycache_init), GFP_NOWAIT);
> -
> - BUG_ON(cpu_cache_get(kmalloc_caches[INDEX_AC])
> - != &initarray_generic.cache);
> - memcpy(ptr, cpu_cache_get(kmalloc_caches[INDEX_AC]),
> - sizeof(struct arraycache_init));
> -
> - kmalloc_caches[INDEX_AC]->array[smp_processor_id()] = ptr;
> - }
> /* 5) Replace the bootstrap kmem_cache_node */
> {
> int nid;
> @@ -1502,13 +1448,8 @@ void __init kmem_cache_init(void)
> for_each_online_node(nid) {
> init_list(kmem_cache, &init_kmem_cache_node[CACHE_CACHE + nid], nid);
>
> - init_list(kmalloc_caches[INDEX_AC],
> - &init_kmem_cache_node[SIZE_AC + nid], nid);
> -
> - if (INDEX_AC != INDEX_NODE) {
> - init_list(kmalloc_caches[INDEX_NODE],
> + init_list(kmalloc_caches[INDEX_NODE],
> &init_kmem_cache_node[SIZE_NODE + nid], nid);
> - }
> }
> }
>
> @@ -2041,56 +1982,63 @@ static size_t calculate_slab_order(struct kmem_cache *cachep,
> return left_over;
> }
>
> +static struct array_cache __percpu *__alloc_kmem_cache_cpus(
> + struct kmem_cache *cachep, int entries, int batchcount)
> +{
> + int cpu;
> + size_t size;
> + struct array_cache __percpu *cpu_cache;
> +
> + size = sizeof(void *) * entries + sizeof(struct array_cache);
> + cpu_cache = __alloc_percpu(size, 0);
> +
> + if (!cpu_cache)
> + return NULL;
> +
> + for_each_possible_cpu(cpu) {
> + init_arraycache(per_cpu_ptr(cpu_cache, cpu),
> + entries, batchcount);
> + }
> +
> + return cpu_cache;
> +}
> +
> +static int alloc_kmem_cache_cpus(struct kmem_cache *cachep, int entries,
> + int batchcount)
> +{
> + cachep->cpu_cache = __alloc_kmem_cache_cpus(cachep, entries,
> + batchcount);
> + if (!cachep->cpu_cache)
> + return 1;
> +
> + return 0;
> +}
> +
> static int __init_refok setup_cpu_cache(struct kmem_cache *cachep, gfp_t gfp)
> {
> if (slab_state >= FULL)
> return enable_cpucache(cachep, gfp);
>
> + if (alloc_kmem_cache_cpus(cachep, 1, 1))
> + return 1;
> +
> if (slab_state == DOWN) {
> - /*
> - * Note: Creation of first cache (kmem_cache).
> - * The setup_node is taken care
> - * of by the caller of __kmem_cache_create
> - */
> - cachep->array[smp_processor_id()] = &initarray_generic.cache;
> - slab_state = PARTIAL;
> + /* Creation of first cache (kmem_cache). */
> + set_up_node(kmem_cache, CACHE_CACHE);
> } else if (slab_state == PARTIAL) {
> - /*
> - * Note: the second kmem_cache_create must create the cache
> - * that's used by kmalloc(24), otherwise the creation of
> - * further caches will BUG().
> - */
> - cachep->array[smp_processor_id()] = &initarray_generic.cache;
> -
> - /*
> - * If the cache that's used by kmalloc(sizeof(kmem_cache_node)) is
> - * the second cache, then we need to set up all its node/,
> - * otherwise the creation of further caches will BUG().
> - */
> - set_up_node(cachep, SIZE_AC);
> - if (INDEX_AC == INDEX_NODE)
> - slab_state = PARTIAL_NODE;
> - else
> - slab_state = PARTIAL_ARRAYCACHE;
> + /* For kmem_cache_node */
> + set_up_node(cachep, SIZE_NODE);
> } else {
> - /* Remaining boot caches */
> - cachep->array[smp_processor_id()] =
> - kmalloc(sizeof(struct arraycache_init), gfp);
> + int node;
>
> - if (slab_state == PARTIAL_ARRAYCACHE) {
> - set_up_node(cachep, SIZE_NODE);
> - slab_state = PARTIAL_NODE;
> - } else {
> - int node;
> - for_each_online_node(node) {
> - cachep->node[node] =
> - kmalloc_node(sizeof(struct kmem_cache_node),
> - gfp, node);
> - BUG_ON(!cachep->node[node]);
> - kmem_cache_node_init(cachep->node[node]);
> - }
> + for_each_online_node(node) {
> + cachep->node[node] = kmalloc_node(
> + sizeof(struct kmem_cache_node), gfp, node);
> + BUG_ON(!cachep->node[node]);
> + kmem_cache_node_init(cachep->node[node]);
> }
> }
> +
> cachep->node[numa_mem_id()]->next_reap =
> jiffies + REAPTIMEOUT_NODE +
> ((unsigned long)cachep) % REAPTIMEOUT_NODE;
> @@ -2194,7 +2142,6 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
> else
> gfp = GFP_NOWAIT;
>
> - setup_node_pointer(cachep);
> #if DEBUG
>
> /*
> @@ -2451,8 +2398,7 @@ int __kmem_cache_shutdown(struct kmem_cache *cachep)
> if (rc)
> return rc;
>
> - for_each_online_cpu(i)
> - kfree(cachep->array[i]);
> + free_percpu(cachep->cpu_cache);
>
> /* NUMA: free the node structures */
> for_each_kmem_cache_node(cachep, i, n) {
> @@ -3700,72 +3646,45 @@ fail:
> return -ENOMEM;
> }
>
> -struct ccupdate_struct {
> - struct kmem_cache *cachep;
> - struct array_cache *new[0];
> -};
> -
> -static void do_ccupdate_local(void *info)
> -{
> - struct ccupdate_struct *new = info;
> - struct array_cache *old;
> -
> - check_irq_off();
> - old = cpu_cache_get(new->cachep);
> -
> - new->cachep->array[smp_processor_id()] = new->new[smp_processor_id()];
> - new->new[smp_processor_id()] = old;
> -}
> -
> /* Always called with the slab_mutex held */
> static int __do_tune_cpucache(struct kmem_cache *cachep, int limit,
> int batchcount, int shared, gfp_t gfp)
> {
> - struct ccupdate_struct *new;
> - int i;
> + struct array_cache __percpu *cpu_cache, *prev;
> + int cpu;
>
> - new = kzalloc(sizeof(*new) + nr_cpu_ids * sizeof(struct array_cache *),
> - gfp);
> - if (!new)
> + cpu_cache = __alloc_kmem_cache_cpus(cachep, limit, batchcount);
> + if (!cpu_cache)
> return -ENOMEM;
>
> - for_each_online_cpu(i) {
> - new->new[i] = alloc_arraycache(cpu_to_mem(i), limit,
> - batchcount, gfp);
> - if (!new->new[i]) {
> - for (i--; i >= 0; i--)
> - kfree(new->new[i]);
> - kfree(new);
> - return -ENOMEM;
> - }
> - }
> - new->cachep = cachep;
> -
> - on_each_cpu(do_ccupdate_local, (void *)new, 1);
> + prev = cachep->cpu_cache;
> + cachep->cpu_cache = cpu_cache;
> + kick_all_cpus_sync();
>
> check_irq_on();
> cachep->batchcount = batchcount;
> cachep->limit = limit;
> cachep->shared = shared;
>
> - for_each_online_cpu(i) {
> + if (!prev)
> + goto alloc_node;
> +
> + for_each_online_cpu(cpu) {
> LIST_HEAD(list);
> - struct array_cache *ccold = new->new[i];
> int node;
> struct kmem_cache_node *n;
> + struct array_cache *ac = per_cpu_ptr(prev, cpu);
>
> - if (!ccold)
> - continue;
> -
> - node = cpu_to_mem(i);
> + node = cpu_to_mem(cpu);
> n = get_node(cachep, node);
> spin_lock_irq(&n->list_lock);
> - free_block(cachep, ccold->entry, ccold->avail, node, &list);
> + free_block(cachep, ac->entry, ac->avail, node, &list);
> spin_unlock_irq(&n->list_lock);
> slabs_destroy(cachep, &list);
> - kfree(ccold);
> }
> - kfree(new);
> + free_percpu(prev);
> +
> +alloc_node:
> return alloc_kmem_cache_node(cachep, gfp);
> }
>
> diff --git a/mm/slab.h b/mm/slab.h
> index bd1c54a..5cb4649 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -48,7 +48,6 @@ struct kmem_cache {
> enum slab_state {
> DOWN, /* No slab functionality yet */
> PARTIAL, /* SLUB: kmem_cache_node available */
> - PARTIAL_ARRAYCACHE, /* SLAB: kmalloc size for arraycache available */
> PARTIAL_NODE, /* SLAB: kmalloc size for node struct available */
> UP, /* Slab caches usable but not all extras yet */
> FULL /* Everything is working */
> --
> 1.7.9.5
>
> --
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I just encountered a problem on a Lenovo Carbon X1 where it will
suspend but won't resume. A bisect indicated that this patch
is causing the problem.
997888488ef92da365b870247de773255227ce1f
I imagine the patch author, Joonsoo Kim, might have a better idea
why this is happening than I do. But if I can provide any information
or run any tests that might be of help just let me know.
--
Jeremiah Mahler
jmmahler@xxxxxxxxx
http://github.com/jmahler
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