Re: [PATCH RFC v3 2/8] slab: add opt-in caching layer of percpu sheaves
From: Suren Baghdasaryan
Date: Thu Apr 10 2025 - 15:52:07 EST
On Mon, Mar 17, 2025 at 7:33 AM Vlastimil Babka <vbabka@xxxxxxx> wrote:
>
> Specifying a non-zero value for a new struct kmem_cache_args field
> sheaf_capacity will setup a caching layer of percpu arrays called
> sheaves of given capacity for the created cache.
>
> Allocations from the cache will allocate via the percpu sheaves (main or
> spare) as long as they have no NUMA node preference. Frees will also
> refill one of the sheaves.
>
> When both percpu sheaves are found empty during an allocation, an empty
> sheaf may be replaced with a full one from the per-node barn. If none
> are available and the allocation is allowed to block, an empty sheaf is
> refilled from slab(s) by an internal bulk alloc operation. When both
> percpu sheaves are full during freeing, the barn can replace a full one
> with an empty one, unless over a full sheaves limit. In that case a
> sheaf is flushed to slab(s) by an internal bulk free operation. Flushing
> sheaves and barns is also wired to the existing cpu flushing and cache
> shrinking operations.
>
> The sheaves do not distinguish NUMA locality of the cached objects. If
> an allocation is requested with kmem_cache_alloc_node() with a specific
> node (not NUMA_NO_NODE), sheaves are bypassed.
>
> The bulk operations exposed to slab users also try to utilize the
> sheaves as long as the necessary (full or empty) sheaves are available
> on the cpu or in the barn. Once depleted, they will fallback to bulk
> alloc/free to slabs directly to avoid double copying.
>
> Sysfs stat counters alloc_cpu_sheaf and free_cpu_sheaf count objects
> allocated or freed using the sheaves. Counters sheaf_refill,
> sheaf_flush_main and sheaf_flush_other count objects filled or flushed
> from or to slab pages, and can be used to assess how effective the
> caching is. The refill and flush operations will also count towards the
> usual alloc_fastpath/slowpath, free_fastpath/slowpath and other
> counters.
>
> Access to the percpu sheaves is protected by localtry_trylock() when
> potential callers include irq context, and localtry_lock() otherwise
> (such as when we already know the gfp flags allow blocking). The trylock
> failures should be rare and we can easily fallback. Each per-NUMA-node
> barn has a spin_lock.
>
> A current limitation is that when slub_debug is enabled for a cache with
> percpu sheaves, the objects in the array are considered as allocated from
> the slub_debug perspective, and the alloc/free debugging hooks occur
> when moving the objects between the array and slab pages. This means
> that e.g. an use-after-free that occurs for an object cached in the
> array is undetected. Collected alloc/free stacktraces might also be less
> useful. This limitation could be changed in the future.
>
> On the other hand, KASAN, kmemcg and other hooks are executed on actual
> allocations and frees by kmem_cache users even if those use the array,
> so their debugging or accounting accuracy should be unaffected.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> include/linux/slab.h | 34 ++
> mm/slab.h | 2 +
> mm/slab_common.c | 5 +-
> mm/slub.c | 1029 +++++++++++++++++++++++++++++++++++++++++++++++---
> 4 files changed, 1020 insertions(+), 50 deletions(-)
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 7686054dd494cc65def7f58748718e03eb78e481..0e1b25228c77140d05b5b4433c9d7923de36ec05 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -332,6 +332,40 @@ struct kmem_cache_args {
> * %NULL means no constructor.
> */
> void (*ctor)(void *);
> + /**
> + * @sheaf_capacity: Enable sheaves of given capacity for the cache.
> + *
> + * With a non-zero value, allocations from the cache go through caching
> + * arrays called sheaves. Each cpu has a main sheaf that's always
> + * present, and a spare sheaf thay may be not present. When both become
> + * empty, there's an attempt to replace an empty sheaf with a full sheaf
> + * from the per-node barn.
> + *
> + * When no full sheaf is available, and gfp flags allow blocking, a
> + * sheaf is allocated and filled from slab(s) using bulk allocation.
> + * Otherwise the allocation falls back to the normal operation
> + * allocating a single object from a slab.
> + *
> + * Analogically when freeing and both percpu sheaves are full, the barn
> + * may replace it with an empty sheaf, unless it's over capacity. In
> + * that case a sheaf is bulk freed to slab pages.
> + *
> + * The sheaves does not distinguish NUMA placement of objects, so
> + * allocations via kmem_cache_alloc_node() with a node specified other
> + * than NUMA_NO_NODE will bypass them.
> + *
> + * Bulk allocation and free operations also try to use the cpu sheaves
> + * and barn, but fallback to using slab pages directly.
> + *
> + * Limitations: when slub_debug is enabled for the cache, all relevant
> + * actions (i.e. poisoning, obtaining stacktraces) and checks happen
> + * when objects move between sheaves and slab pages, which may result in
> + * e.g. not detecting a use-after-free while the object is in the array
> + * cache, and the stacktraces may be less useful.
> + *
> + * %0 means no sheaves will be created
> + */
> + unsigned int sheaf_capacity;
> };
>
> struct kmem_cache *__kmem_cache_create_args(const char *name,
> diff --git a/mm/slab.h b/mm/slab.h
> index 2f01c7317988ce036f0b22807403226a59f0f708..8daaec53b6ecfc44171191d421adb12e5cba2c58 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -259,6 +259,7 @@ struct kmem_cache {
> #ifndef CONFIG_SLUB_TINY
> struct kmem_cache_cpu __percpu *cpu_slab;
> #endif
> + struct slub_percpu_sheaves __percpu *cpu_sheaves;
> /* Used for retrieving partial slabs, etc. */
> slab_flags_t flags;
> unsigned long min_partial;
> @@ -272,6 +273,7 @@ struct kmem_cache {
> /* Number of per cpu partial slabs to keep around */
> unsigned int cpu_partial_slabs;
> #endif
> + unsigned int sheaf_capacity;
> struct kmem_cache_order_objects oo;
>
> /* Allocation and freeing of slabs */
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 46d0a4cd33b5982fd79c307d572f231fdea9514a..ceeefb287899a82f30ad79b403556001c1860311 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -163,6 +163,9 @@ int slab_unmergeable(struct kmem_cache *s)
> return 1;
> #endif
>
> + if (s->cpu_sheaves)
> + return 1;
> +
> /*
> * We may have set a slab to be unmergeable during bootstrap.
> */
> @@ -328,7 +331,7 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,
> object_size - args->usersize < args->useroffset))
> args->usersize = args->useroffset = 0;
>
> - if (!args->usersize)
> + if (!args->usersize && !args->sheaf_capacity)
> s = __kmem_cache_alias(name, object_size, args->align, flags,
> args->ctor);
> if (s)
> diff --git a/mm/slub.c b/mm/slub.c
> index e8273f28656936c05d015c53923f8fe69cd161b2..fa3a6329713a9f45b189f27d4b1b334b54589c38 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -346,8 +346,10 @@ static inline void debugfs_slab_add(struct kmem_cache *s) { }
> #endif
>
> enum stat_item {
> + ALLOC_PCS, /* Allocation from percpu sheaf */
> ALLOC_FASTPATH, /* Allocation from cpu slab */
> ALLOC_SLOWPATH, /* Allocation by getting a new cpu slab */
> + FREE_PCS, /* Free to percpu sheaf */
> FREE_FASTPATH, /* Free to cpu slab */
> FREE_SLOWPATH, /* Freeing not to cpu slab */
> FREE_FROZEN, /* Freeing to frozen slab */
> @@ -372,6 +374,12 @@ enum stat_item {
> CPU_PARTIAL_FREE, /* Refill cpu partial on free */
> CPU_PARTIAL_NODE, /* Refill cpu partial from node partial */
> CPU_PARTIAL_DRAIN, /* Drain cpu partial to node partial */
> + SHEAF_FLUSH_MAIN, /* Objects flushed from main percpu sheaf */
> + SHEAF_FLUSH_OTHER, /* Objects flushed from other sheaves */
> + SHEAF_REFILL, /* Objects refilled to a sheaf */
> + SHEAF_SWAP, /* Swapping main and spare sheaf */
> + SHEAF_ALLOC, /* Allocation of an empty sheaf */
> + SHEAF_FREE, /* Freeing of an empty sheaf */
> NR_SLUB_STAT_ITEMS
> };
>
> @@ -418,6 +426,33 @@ void stat_add(const struct kmem_cache *s, enum stat_item si, int v)
> #endif
> }
>
> +#define MAX_FULL_SHEAVES 10
> +#define MAX_EMPTY_SHEAVES 10
> +
> +struct node_barn {
> + spinlock_t lock;
> + struct list_head sheaves_full;
> + struct list_head sheaves_empty;
> + unsigned int nr_full;
> + unsigned int nr_empty;
> +};
> +
> +struct slab_sheaf {
> + union {
> + struct rcu_head rcu_head;
> + struct list_head barn_list;
> + };
> + unsigned int size;
> + void *objects[];
> +};
> +
> +struct slub_percpu_sheaves {
> + localtry_lock_t lock;
> + struct slab_sheaf *main; /* never NULL when unlocked */
> + struct slab_sheaf *spare; /* empty or full, may be NULL */
> + struct node_barn *barn;
> +};
> +
> /*
> * The slab lists for all objects.
> */
> @@ -430,6 +465,7 @@ struct kmem_cache_node {
> atomic_long_t total_objects;
> struct list_head full;
> #endif
> + struct node_barn *barn;
> };
>
> static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
> @@ -453,12 +489,19 @@ static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
> */
> static nodemask_t slab_nodes;
>
> -#ifndef CONFIG_SLUB_TINY
> /*
> * Workqueue used for flush_cpu_slab().
> */
> static struct workqueue_struct *flushwq;
> -#endif
> +
> +struct slub_flush_work {
> + struct work_struct work;
> + struct kmem_cache *s;
> + bool skip;
> +};
> +
> +static DEFINE_MUTEX(flush_lock);
> +static DEFINE_PER_CPU(struct slub_flush_work, slub_flush);
>
> /********************************************************************
> * Core slab cache functions
> @@ -2410,6 +2453,358 @@ static void *setup_object(struct kmem_cache *s, void *object)
> return object;
> }
>
> +static struct slab_sheaf *alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp)
> +{
> + struct slab_sheaf *sheaf = kzalloc(struct_size(sheaf, objects,
> + s->sheaf_capacity), gfp);
> +
> + if (unlikely(!sheaf))
> + return NULL;
> +
> + stat(s, SHEAF_ALLOC);
> +
> + return sheaf;
> +}
> +
> +static void free_empty_sheaf(struct kmem_cache *s, struct slab_sheaf *sheaf)
> +{
> + kfree(sheaf);
> +
> + stat(s, SHEAF_FREE);
> +}
> +
> +static int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
> + size_t size, void **p);
> +
> +
> +static int refill_sheaf(struct kmem_cache *s, struct slab_sheaf *sheaf,
> + gfp_t gfp)
> +{
> + int to_fill = s->sheaf_capacity - sheaf->size;
> + int filled;
> +
> + if (!to_fill)
> + return 0;
> +
> + filled = __kmem_cache_alloc_bulk(s, gfp, to_fill,
> + &sheaf->objects[sheaf->size]);
> +
> + sheaf->size += filled;
> +
> + stat_add(s, SHEAF_REFILL, filled);
> +
> + if (filled < to_fill)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +
> +static struct slab_sheaf *alloc_full_sheaf(struct kmem_cache *s, gfp_t gfp)
> +{
> + struct slab_sheaf *sheaf = alloc_empty_sheaf(s, gfp);
> +
> + if (!sheaf)
> + return NULL;
> +
> + if (refill_sheaf(s, sheaf, gfp)) {
> + free_empty_sheaf(s, sheaf);
> + return NULL;
> + }
> +
> + return sheaf;
> +}
> +
> +/*
> + * Maximum number of objects freed during a single flush of main pcs sheaf.
> + * Translates directly to an on-stack array size.
> + */
> +#define PCS_BATCH_MAX 32U
> +
> +static void __kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p);
> +
> +/*
> + * Free all objects from the main sheaf. In order to perform
> + * __kmem_cache_free_bulk() outside of cpu_sheaves->lock, work in batches where
> + * object pointers are moved to a on-stack array under the lock. To bound the
> + * stack usage, limit each batch to PCS_BATCH_MAX.
> + *
> + * returns true if at least partially flushed
> + */
> +static bool sheaf_flush_main(struct kmem_cache *s)
> +{
> + struct slub_percpu_sheaves *pcs;
> + unsigned int batch, remaining;
> + void *objects[PCS_BATCH_MAX];
> + struct slab_sheaf *sheaf;
> + bool ret = false;
> +
> +next_batch:
> + if (!localtry_trylock(&s->cpu_sheaves->lock))
> + return ret;
> +
> + pcs = this_cpu_ptr(s->cpu_sheaves);
> + sheaf = pcs->main;
> +
> + batch = min(PCS_BATCH_MAX, sheaf->size);
> +
> + sheaf->size -= batch;
> + memcpy(objects, sheaf->objects + sheaf->size, batch * sizeof(void *));
> +
> + remaining = sheaf->size;
> +
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + __kmem_cache_free_bulk(s, batch, &objects[0]);
> +
> + stat_add(s, SHEAF_FLUSH_MAIN, batch);
> +
> + ret = true;
> +
> + if (remaining)
> + goto next_batch;
> +
> + return ret;
> +}
> +
> +/*
> + * Free all objects from a sheaf that's unused, i.e. not linked to any
> + * cpu_sheaves, so we need no locking and batching. The locking is also not
> + * necessary when flushing cpu's sheaves (both spare and main) during cpu
> + * hotremove as the cpu is not executing anymore.
> + */
> +static void sheaf_flush_unused(struct kmem_cache *s, struct slab_sheaf *sheaf)
> +{
> + if (!sheaf->size)
> + return;
> +
> + stat_add(s, SHEAF_FLUSH_OTHER, sheaf->size);
> +
> + __kmem_cache_free_bulk(s, sheaf->size, &sheaf->objects[0]);
> +
> + sheaf->size = 0;
> +}
> +
> +/*
> + * Caller needs to make sure migration is disabled in order to fully flush
> + * single cpu's sheaves
> + *
> + * must not be called from an irq
> + *
> + * flushing operations are rare so let's keep it simple and flush to slabs
> + * directly, skipping the barn
> + */
> +static void pcs_flush_all(struct kmem_cache *s)
> +{
> + struct slub_percpu_sheaves *pcs;
> + struct slab_sheaf *spare;
> +
> + localtry_lock(&s->cpu_sheaves->lock);
> + pcs = this_cpu_ptr(s->cpu_sheaves);
> +
> + spare = pcs->spare;
> + pcs->spare = NULL;
> +
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + if (spare) {
> + sheaf_flush_unused(s, spare);
> + free_empty_sheaf(s, spare);
> + }
> +
> + sheaf_flush_main(s);
> +}
> +
> +static void __pcs_flush_all_cpu(struct kmem_cache *s, unsigned int cpu)
> +{
> + struct slub_percpu_sheaves *pcs;
> +
> + pcs = per_cpu_ptr(s->cpu_sheaves, cpu);
> +
> + /* The cpu is not executing anymore so we don't need pcs->lock */
> + sheaf_flush_unused(s, pcs->main);
You are flushing pcs->main but sheaf_flush_unused() will account that
in SHEAF_FLUSH_OTHER instead of SHEAF_FLUSH_MAIN. Perhaps
sheaf_flush_unused() needs a parameter to indicate which counter to be
incremented.
> + if (pcs->spare) {
> + sheaf_flush_unused(s, pcs->spare);
> + free_empty_sheaf(s, pcs->spare);
> + pcs->spare = NULL;
> + }
> +}
> +
> +static void pcs_destroy(struct kmem_cache *s)
> +{
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + struct slub_percpu_sheaves *pcs;
> +
> + pcs = per_cpu_ptr(s->cpu_sheaves, cpu);
> +
> + /* can happen when unwinding failed create */
> + if (!pcs->main)
> + continue;
> +
> + WARN_ON(pcs->spare);
> +
> + if (!WARN_ON(pcs->main->size)) {
If pcs->main->size > 0, shouldn't we flush pcs->main? I understand
it's not a normal situation but I think something like this would be
more correct:
if (WARN_ON(pcs->main->size))
sheaf_flush_unused(s, pcs->main);
free_empty_sheaf(s, pcs->main);
pcs->main = NULL;
> + free_empty_sheaf(s, pcs->main);
> + pcs->main = NULL;
> + }
> + }
> +
> + free_percpu(s->cpu_sheaves);
> + s->cpu_sheaves = NULL;
> +}
> +
> +static struct slab_sheaf *barn_get_empty_sheaf(struct node_barn *barn)
> +{
> + struct slab_sheaf *empty = NULL;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&barn->lock, flags);
> +
> + if (barn->nr_empty) {
> + empty = list_first_entry(&barn->sheaves_empty,
> + struct slab_sheaf, barn_list);
> + list_del(&empty->barn_list);
> + barn->nr_empty--;
> + }
> +
> + spin_unlock_irqrestore(&barn->lock, flags);
> +
> + return empty;
> +}
> +
> +static int barn_put_empty_sheaf(struct node_barn *barn,
> + struct slab_sheaf *sheaf, bool ignore_limit)
This ignore_limit in barn_put_empty_sheaf()/barn_put_full_sheaf() is
sticking out and really used only inside rcu_free_sheaf() in the next
patch. Every time I saw the return value of these functions ignored I
had to remind myself that they pass ignore_limit=true, so the function
can't really fail. Maybe we could get rid of this flag and do trimming
of barn lists inside rcu_free_sheaf() separately in one go? IIUC
because we ignore the limits in all other places, at the time of
rcu_free_sheaf() we might end up with a barn having many more sheaves
than the limit allows for, so trimming in bulk might be even more
productive.
> +{
> + unsigned long flags;
> + int ret = 0;
> +
> + spin_lock_irqsave(&barn->lock, flags);
> +
> + if (!ignore_limit && barn->nr_empty >= MAX_EMPTY_SHEAVES) {
> + ret = -E2BIG;
> + } else {
> + list_add(&sheaf->barn_list, &barn->sheaves_empty);
> + barn->nr_empty++;
> + }
> +
> + spin_unlock_irqrestore(&barn->lock, flags);
> + return ret;
> +}
> +
> +static int barn_put_full_sheaf(struct node_barn *barn, struct slab_sheaf *sheaf,
> + bool ignore_limit)
Can this function be called for partially populated sheaves or only
full ones? I think rcu_free_sheaf() in the next patch might end up
calling it for a partially populated sheaf.
> +{
> + unsigned long flags;
> + int ret = 0;
> +
> + spin_lock_irqsave(&barn->lock, flags);
> +
> + if (!ignore_limit && barn->nr_full >= MAX_FULL_SHEAVES) {
> + ret = -E2BIG;
> + } else {
> + list_add(&sheaf->barn_list, &barn->sheaves_full);
> + barn->nr_full++;
> + }
> +
> + spin_unlock_irqrestore(&barn->lock, flags);
> + return ret;
> +}
> +
> +/*
> + * If a full sheaf is available, return it and put the supplied empty one to
> + * barn. We ignore the limit on empty sheaves as the number of sheaves doesn't
> + * change.
I'm unclear why we ignore the limit here but not in
barn_replace_full_sheaf(). Maybe because full sheaves consume more
memory? But then why do we mostly pass ignore_limit=true when invoking
barn_put_full_sheaf()? Explanation of this limit logic needs to be
clarified.
> + */
> +static struct slab_sheaf *
> +barn_replace_empty_sheaf(struct node_barn *barn, struct slab_sheaf *empty)
> +{
> + struct slab_sheaf *full = NULL;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&barn->lock, flags);
> +
> + if (barn->nr_full) {
> + full = list_first_entry(&barn->sheaves_full, struct slab_sheaf,
> + barn_list);
> + list_del(&full->barn_list);
> + list_add(&empty->barn_list, &barn->sheaves_empty);
> + barn->nr_full--;
> + barn->nr_empty++;
> + }
> +
> + spin_unlock_irqrestore(&barn->lock, flags);
> +
> + return full;
> +}
> +/*
> + * If a empty sheaf is available, return it and put the supplied full one to
> + * barn. But if there are too many full sheaves, reject this with -E2BIG.
> + */
> +static struct slab_sheaf *
> +barn_replace_full_sheaf(struct node_barn *barn, struct slab_sheaf *full)
> +{
> + struct slab_sheaf *empty;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&barn->lock, flags);
> +
> + if (barn->nr_full >= MAX_FULL_SHEAVES) {
> + empty = ERR_PTR(-E2BIG);
> + } else if (!barn->nr_empty) {
> + empty = ERR_PTR(-ENOMEM);
> + } else {
> + empty = list_first_entry(&barn->sheaves_empty, struct slab_sheaf,
> + barn_list);
> + list_del(&empty->barn_list);
> + list_add(&full->barn_list, &barn->sheaves_full);
> + barn->nr_empty--;
> + barn->nr_full++;
> + }
> +
> + spin_unlock_irqrestore(&barn->lock, flags);
> +
> + return empty;
> +}
> +
> +static void barn_init(struct node_barn *barn)
> +{
> + spin_lock_init(&barn->lock);
> + INIT_LIST_HEAD(&barn->sheaves_full);
> + INIT_LIST_HEAD(&barn->sheaves_empty);
> + barn->nr_full = 0;
> + barn->nr_empty = 0;
> +}
> +
> +static void barn_shrink(struct kmem_cache *s, struct node_barn *barn)
> +{
> + struct list_head empty_list;
> + struct list_head full_list;
> + struct slab_sheaf *sheaf, *sheaf2;
> + unsigned long flags;
> +
> + INIT_LIST_HEAD(&empty_list);
> + INIT_LIST_HEAD(&full_list);
> +
> + spin_lock_irqsave(&barn->lock, flags);
> +
> + list_splice_init(&barn->sheaves_full, &full_list);
> + barn->nr_full = 0;
> + list_splice_init(&barn->sheaves_empty, &empty_list);
> + barn->nr_empty = 0;
> +
> + spin_unlock_irqrestore(&barn->lock, flags);
> +
> + list_for_each_entry_safe(sheaf, sheaf2, &full_list, barn_list) {
> + sheaf_flush_unused(s, sheaf);
> + free_empty_sheaf(s, sheaf);
> + }
> +
> + list_for_each_entry_safe(sheaf, sheaf2, &empty_list, barn_list)
> + free_empty_sheaf(s, sheaf);
> +}
> +
> /*
> * Slab allocation and freeing
> */
> @@ -3280,11 +3675,42 @@ static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu)
> put_partials_cpu(s, c);
> }
>
> -struct slub_flush_work {
> - struct work_struct work;
> - struct kmem_cache *s;
> - bool skip;
> -};
> +static inline void flush_this_cpu_slab(struct kmem_cache *s)
> +{
> + struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab);
> +
> + if (c->slab)
> + flush_slab(s, c);
> +
> + put_partials(s);
> +}
> +
> +static bool has_cpu_slab(int cpu, struct kmem_cache *s)
> +{
> + struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
> +
> + return c->slab || slub_percpu_partial(c);
> +}
> +
> +#else /* CONFIG_SLUB_TINY */
> +static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu) { }
> +static inline bool has_cpu_slab(int cpu, struct kmem_cache *s) { return false; }
> +static inline void flush_this_cpu_slab(struct kmem_cache *s) { }
> +#endif /* CONFIG_SLUB_TINY */
> +
> +static bool has_pcs_used(int cpu, struct kmem_cache *s)
> +{
> + struct slub_percpu_sheaves *pcs;
> +
> + if (!s->cpu_sheaves)
> + return false;
> +
> + pcs = per_cpu_ptr(s->cpu_sheaves, cpu);
> +
> + return (pcs->spare || pcs->main->size);
> +}
> +
> +static void pcs_flush_all(struct kmem_cache *s);
>
> /*
> * Flush cpu slab.
> @@ -3294,30 +3720,18 @@ struct slub_flush_work {
> static void flush_cpu_slab(struct work_struct *w)
> {
> struct kmem_cache *s;
> - struct kmem_cache_cpu *c;
> struct slub_flush_work *sfw;
>
> sfw = container_of(w, struct slub_flush_work, work);
>
> s = sfw->s;
> - c = this_cpu_ptr(s->cpu_slab);
> -
> - if (c->slab)
> - flush_slab(s, c);
> -
> - put_partials(s);
> -}
>
> -static bool has_cpu_slab(int cpu, struct kmem_cache *s)
> -{
> - struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
> + if (s->cpu_sheaves)
> + pcs_flush_all(s);
>
> - return c->slab || slub_percpu_partial(c);
> + flush_this_cpu_slab(s);
> }
>
> -static DEFINE_MUTEX(flush_lock);
> -static DEFINE_PER_CPU(struct slub_flush_work, slub_flush);
> -
> static void flush_all_cpus_locked(struct kmem_cache *s)
> {
> struct slub_flush_work *sfw;
> @@ -3328,7 +3742,7 @@ static void flush_all_cpus_locked(struct kmem_cache *s)
>
> for_each_online_cpu(cpu) {
> sfw = &per_cpu(slub_flush, cpu);
> - if (!has_cpu_slab(cpu, s)) {
> + if (!has_cpu_slab(cpu, s) && !has_pcs_used(cpu, s)) {
> sfw->skip = true;
> continue;
> }
> @@ -3364,19 +3778,14 @@ static int slub_cpu_dead(unsigned int cpu)
> struct kmem_cache *s;
>
> mutex_lock(&slab_mutex);
> - list_for_each_entry(s, &slab_caches, list)
> + list_for_each_entry(s, &slab_caches, list) {
> __flush_cpu_slab(s, cpu);
> + __pcs_flush_all_cpu(s, cpu);
> + }
> mutex_unlock(&slab_mutex);
> return 0;
> }
>
> -#else /* CONFIG_SLUB_TINY */
> -static inline void flush_all_cpus_locked(struct kmem_cache *s) { }
> -static inline void flush_all(struct kmem_cache *s) { }
> -static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu) { }
> -static inline int slub_cpu_dead(unsigned int cpu) { return 0; }
> -#endif /* CONFIG_SLUB_TINY */
> -
> /*
> * Check if the objects in a per cpu structure fit numa
> * locality expectations.
> @@ -4126,6 +4535,179 @@ bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
> return memcg_slab_post_alloc_hook(s, lru, flags, size, p);
> }
>
> +static __fastpath_inline
> +void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp)
> +{
> + struct slub_percpu_sheaves *pcs;
> + void *object;
> +
> + if (!localtry_trylock(&s->cpu_sheaves->lock))
> + return NULL;
> +
> + pcs = this_cpu_ptr(s->cpu_sheaves);
> +
> + if (unlikely(pcs->main->size == 0)) {
> +
> + struct slab_sheaf *empty = NULL;
> + struct slab_sheaf *full;
> + bool can_alloc;
> +
> + if (pcs->spare && pcs->spare->size > 0) {
> + stat(s, SHEAF_SWAP);
> + swap(pcs->main, pcs->spare);
> + goto do_alloc;
> + }
> +
> + full = barn_replace_empty_sheaf(pcs->barn, pcs->main);
> +
> + if (full) {
> + pcs->main = full;
> + goto do_alloc;
> + }
> +
> + can_alloc = gfpflags_allow_blocking(gfp);
> +
> + if (can_alloc) {
> + if (pcs->spare) {
> + empty = pcs->spare;
> + pcs->spare = NULL;
> + } else {
> + empty = barn_get_empty_sheaf(pcs->barn);
> + }
> + }
> +
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + if (!can_alloc)
> + return NULL;
> +
> + if (empty) {
> + if (!refill_sheaf(s, empty, gfp)) {
> + full = empty;
> + } else {
> + /*
> + * we must be very low on memory so don't bother
> + * with the barn
> + */
> + free_empty_sheaf(s, empty);
> + }
> + } else {
> + full = alloc_full_sheaf(s, gfp);
> + }
> +
> + if (!full)
> + return NULL;
> +
> + /*
> + * we can reach here only when gfpflags_allow_blocking
> + * so this must not be an irq
> + */
> + localtry_lock(&s->cpu_sheaves->lock);
> + pcs = this_cpu_ptr(s->cpu_sheaves);
> +
> + /*
> + * If we are returning empty sheaf, we either got it from the
> + * barn or had to allocate one. If we are returning a full
> + * sheaf, it's due to racing or being migrated to a different
> + * cpu. Breaching the barn's sheaf limits should be thus rare
> + * enough so just ignore them to simplify the recovery.
> + */
> +
> + if (pcs->main->size == 0) {
> + barn_put_empty_sheaf(pcs->barn, pcs->main, true);
> + pcs->main = full;
> + goto do_alloc;
> + }
> +
> + if (!pcs->spare) {
> + pcs->spare = full;
> + goto do_alloc;
> + }
> +
> + if (pcs->spare->size == 0) {
> + barn_put_empty_sheaf(pcs->barn, pcs->spare, true);
> + pcs->spare = full;
> + goto do_alloc;
> + }
> +
> + barn_put_full_sheaf(pcs->barn, full, true);
> + }
> +
> +do_alloc:
> + object = pcs->main->objects[--pcs->main->size];
> +
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + stat(s, ALLOC_PCS);
> +
> + return object;
> +}
> +
> +static __fastpath_inline
> +unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, size_t size, void **p)
> +{
> + struct slub_percpu_sheaves *pcs;
> + struct slab_sheaf *main;
> + unsigned int allocated = 0;
> + unsigned int batch;
> +
> +next_batch:
> + if (!localtry_trylock(&s->cpu_sheaves->lock))
> + return allocated;
> +
> + pcs = this_cpu_ptr(s->cpu_sheaves);
> +
> + if (unlikely(pcs->main->size == 0)) {
The above condition is unlikely only for the first batch. I think it's
actually guaranteed on all consecutive batches once you do "goto
next_batch", right?
> +
> + struct slab_sheaf *full;
> +
> + if (pcs->spare && pcs->spare->size > 0) {
> + stat(s, SHEAF_SWAP);
> + swap(pcs->main, pcs->spare);
> + goto do_alloc;
> + }
> +
> + full = barn_replace_empty_sheaf(pcs->barn, pcs->main);
> +
> + if (full) {
> + pcs->main = full;
> + goto do_alloc;
> + }
> +
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + /*
> + * Once full sheaves in barn are depleted, let the bulk
> + * allocation continue from slab pages, otherwise we would just
> + * be copying arrays of pointers twice.
> + */
> + return allocated;
> + }
> +
> +do_alloc:
> +
> + main = pcs->main;
> + batch = min(size, main->size);
> +
> + main->size -= batch;
> + memcpy(p, main->objects + main->size, batch * sizeof(void *));
> +
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + stat_add(s, ALLOC_PCS, batch);
> +
> + allocated += batch;
> +
> + if (batch < size) {
> + p += batch;
> + size -= batch;
> + goto next_batch;
> + }
> +
> + return allocated;
> +}
> +
> +
> /*
> * Inlined fastpath so that allocation functions (kmalloc, kmem_cache_alloc)
> * have the fastpath folded into their functions. So no function call
> @@ -4150,7 +4732,11 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
> if (unlikely(object))
> goto out;
>
> - object = __slab_alloc_node(s, gfpflags, node, addr, orig_size);
> + if (s->cpu_sheaves && (node == NUMA_NO_NODE))
> + object = alloc_from_pcs(s, gfpflags);
> +
> + if (!object)
> + object = __slab_alloc_node(s, gfpflags, node, addr, orig_size);
>
> maybe_wipe_obj_freeptr(s, object);
> init = slab_want_init_on_alloc(gfpflags, s);
> @@ -4521,6 +5107,232 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
> discard_slab(s, slab);
> }
>
> +/*
> + * pcs is locked. We should have get rid of the spare sheaf and obtained an
> + * empty sheaf, while the main sheaf is full. We want to install the empty sheaf
> + * as a main sheaf, and make the current main sheaf a spare sheaf.
> + *
> + * However due to having relinquished the cpu_sheaves lock when obtaining
> + * the empty sheaf, we need to handle some unlikely but possible cases.
> + *
> + * If we put any sheaf to barn here, it's because we were interrupted or have
> + * been migrated to a different cpu, which should be rare enough so just ignore
> + * the barn's limits to simplify the handling.
> + */
> +static void __pcs_install_empty_sheaf(struct kmem_cache *s,
> + struct slub_percpu_sheaves *pcs, struct slab_sheaf *empty)
> +{
> + /* this is what we expect to find in nobody interrupted us */
s/in/if in the above comment
> + if (likely(!pcs->spare)) {
> + pcs->spare = pcs->main;
> + pcs->main = empty;
> + return;
> + }
> +
> + /*
> + * Unlikely because if the main sheaf had space, we would have just
> + * freed to it. Get rid of our empty sheaf.
> + */
> + if (pcs->main->size < s->sheaf_capacity) {
> + barn_put_empty_sheaf(pcs->barn, empty, true);
> + return;
> + }
> +
> + /* Also unlikely for the same reason */
> + if (pcs->spare->size < s->sheaf_capacity) {
> + stat(s, SHEAF_SWAP);
> + swap(pcs->main, pcs->spare);
> + barn_put_empty_sheaf(pcs->barn, empty, true);
> + return;
> + }
> +
> + barn_put_full_sheaf(pcs->barn, pcs->main, true);
> + pcs->main = empty;
> +}
> +
> +/*
> + * Free an object to the percpu sheaves.
> + * The object is expected to have passed slab_free_hook() already.
> + */
> +static __fastpath_inline
> +bool free_to_pcs(struct kmem_cache *s, void *object)
> +{
> + struct slub_percpu_sheaves *pcs;
> +
> +restart:
> + if (!localtry_trylock(&s->cpu_sheaves->lock))
> + return false;
> +
> + pcs = this_cpu_ptr(s->cpu_sheaves);
> +
> + if (unlikely(pcs->main->size == s->sheaf_capacity)) {
> +
> + struct slab_sheaf *empty;
> +
> + if (!pcs->spare) {
> + empty = barn_get_empty_sheaf(pcs->barn);
> + if (empty) {
> + pcs->spare = pcs->main;
> + pcs->main = empty;
> + goto do_free;
> + }
> + goto alloc_empty;
> + }
> +
> + if (pcs->spare->size < s->sheaf_capacity) {
> + stat(s, SHEAF_SWAP);
> + swap(pcs->main, pcs->spare);
> + goto do_free;
> + }
> +
> + empty = barn_replace_full_sheaf(pcs->barn, pcs->main);
This function reads easier now but if barn_replace_full_sheaf() could
ignore the MAX_FULL_SHEAVES and barn list trimming could be done
later, it would simplify this function even further.
> +
> + if (!IS_ERR(empty)) {
> + pcs->main = empty;
> + goto do_free;
> + }
> +
> + if (PTR_ERR(empty) == -E2BIG) {
> + /* Since we got here, spare exists and is full */
> + struct slab_sheaf *to_flush = pcs->spare;
> +
> + pcs->spare = NULL;
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + sheaf_flush_unused(s, to_flush);
> + empty = to_flush;
> + goto got_empty;
> + }
> +
> +alloc_empty:
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + empty = alloc_empty_sheaf(s, GFP_NOWAIT);
> +
> + if (!empty) {
> + if (sheaf_flush_main(s))
> + goto restart;
> + else
> + return false;
> + }
> +
> +got_empty:
> + if (!localtry_trylock(&s->cpu_sheaves->lock)) {
> + struct node_barn *barn;
> +
> + barn = get_node(s, numa_mem_id())->barn;
> +
> + barn_put_empty_sheaf(barn, empty, true);
> + return false;
> + }
> +
> + pcs = this_cpu_ptr(s->cpu_sheaves);
> + __pcs_install_empty_sheaf(s, pcs, empty);
> + }
> +
> +do_free:
> + pcs->main->objects[pcs->main->size++] = object;
> +
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + stat(s, FREE_PCS);
> +
> + return true;
> +}
> +
> +/*
> + * Bulk free objects to the percpu sheaves.
> + * Unlike free_to_pcs() this includes the calls to all necessary hooks
> + * and the fallback to freeing to slab pages.
> + */
> +static void free_to_pcs_bulk(struct kmem_cache *s, size_t size, void **p)
> +{
> + struct slub_percpu_sheaves *pcs;
> + struct slab_sheaf *main;
> + unsigned int batch, i = 0;
> + bool init;
> +
> + init = slab_want_init_on_free(s);
> +
> + while (i < size) {
> + struct slab *slab = virt_to_slab(p[i]);
> +
> + memcg_slab_free_hook(s, slab, p + i, 1);
> + alloc_tagging_slab_free_hook(s, slab, p + i, 1);
> +
> + if (unlikely(!slab_free_hook(s, p[i], init, false))) {
> + p[i] = p[--size];
> + if (!size)
> + return;
> + continue;
> + }
> +
> + i++;
> + }
> +
> +next_batch:
nit: I think the section below would be more readable if structured
with fail handling blocks at the end. Something like this:
next_batch:
if (!localtry_trylock(&s->cpu_sheaves->lock))
goto fallback;
pcs = this_cpu_ptr(s->cpu_sheaves);
if (likely(pcs->main->size < s->sheaf_capacity))
goto do_free;
if (!pcs->spare) {
empty = barn_get_empty_sheaf(pcs->barn);
if (!empty)
goto no_empty;
pcs->spare = pcs->main;
pcs->main = empty;
goto do_free;
}
if (pcs->spare->size < s->sheaf_capacity) {
stat(s, SHEAF_SWAP);
swap(pcs->main, pcs->spare);
goto do_free;
}
empty = barn_replace_full_sheaf(pcs->barn, pcs->main);
if (IS_ERR(empty))
goto no_empty;
pcs->main = empty;
do_free:
main = pcs->main;
batch = min(size, s->sheaf_capacity - main->size);
memcpy(main->objects + main->size, p, batch * sizeof(void *));
main->size += batch;
localtry_unlock(&s->cpu_sheaves->lock);
stat_add(s, FREE_PCS, batch);
if (batch < size) {
p += batch;
size -= batch;
goto next_batch;
}
return;
no_empty:
localtry_unlock(&s->cpu_sheaves->lock);
/*
* if we depleted all empty sheaves in the barn or there are too
* many full sheaves, free the rest to slab pages
*/
fallback:
__kmem_cache_free_bulk(s, size, p);
}
> + if (!localtry_trylock(&s->cpu_sheaves->lock))
> + goto fallback;
> +
> + pcs = this_cpu_ptr(s->cpu_sheaves);
> +
> + if (unlikely(pcs->main->size == s->sheaf_capacity)) {
> +
> + struct slab_sheaf *empty;
> +
> + if (!pcs->spare) {
> + empty = barn_get_empty_sheaf(pcs->barn);
> + if (empty) {
> + pcs->spare = pcs->main;
> + pcs->main = empty;
> + goto do_free;
> + }
> + goto no_empty;
> + }
> +
> + if (pcs->spare->size < s->sheaf_capacity) {
> + stat(s, SHEAF_SWAP);
> + swap(pcs->main, pcs->spare);
> + goto do_free;
> + }
> +
> + empty = barn_replace_full_sheaf(pcs->barn, pcs->main);
> +
> + if (!IS_ERR(empty)) {
> + pcs->main = empty;
> + goto do_free;
> + }
> +
> +no_empty:
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + /*
> + * if we depleted all empty sheaves in the barn or there are too
> + * many full sheaves, free the rest to slab pages
> + */
> +fallback:
> + __kmem_cache_free_bulk(s, size, p);
> + return;
> + }
> +
> +do_free:
> + main = pcs->main;
> + batch = min(size, s->sheaf_capacity - main->size);
> +
> + memcpy(main->objects + main->size, p, batch * sizeof(void *));
> + main->size += batch;
> +
> + localtry_unlock(&s->cpu_sheaves->lock);
> +
> + stat_add(s, FREE_PCS, batch);
> +
> + if (batch < size) {
> + p += batch;
> + size -= batch;
> + goto next_batch;
> + }
> +}
> +
> #ifndef CONFIG_SLUB_TINY
> /*
> * Fastpath with forced inlining to produce a kfree and kmem_cache_free that
> @@ -4607,7 +5419,10 @@ void slab_free(struct kmem_cache *s, struct slab *slab, void *object,
> memcg_slab_free_hook(s, slab, &object, 1);
> alloc_tagging_slab_free_hook(s, slab, &object, 1);
>
> - if (likely(slab_free_hook(s, object, slab_want_init_on_free(s), false)))
> + if (unlikely(!slab_free_hook(s, object, slab_want_init_on_free(s), false)))
> + return;
> +
> + if (!s->cpu_sheaves || !free_to_pcs(s, object))
> do_slab_free(s, slab, object, object, 1, addr);
> }
>
> @@ -5033,6 +5848,15 @@ void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
> if (!size)
> return;
>
> + /*
> + * freeing to sheaves is so incompatible with the detached freelist so
> + * once we go that way, we have to do everything differently
> + */
> + if (s && s->cpu_sheaves) {
> + free_to_pcs_bulk(s, size, p);
> + return;
> + }
> +
> do {
> struct detached_freelist df;
>
> @@ -5151,7 +5975,7 @@ static int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
> int kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags, size_t size,
> void **p)
> {
> - int i;
> + unsigned int i = 0;
>
> if (!size)
> return 0;
> @@ -5160,9 +5984,21 @@ int kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags, size_t size,
> if (unlikely(!s))
> return 0;
>
> - i = __kmem_cache_alloc_bulk(s, flags, size, p);
> - if (unlikely(i == 0))
> - return 0;
> + if (s->cpu_sheaves)
> + i = alloc_from_pcs_bulk(s, size, p);
> +
> + if (i < size) {
> + unsigned int j = __kmem_cache_alloc_bulk(s, flags, size - i, p + i);
> + /*
> + * If we ran out of memory, don't bother with freeing back to
> + * the percpu sheaves, we have bigger problems.
> + */
> + if (unlikely(j == 0)) {
> + if (i > 0)
> + __kmem_cache_free_bulk(s, i, p);
> + return 0;
> + }
> + }
>
> /*
> * memcg and kmem_cache debug support and memory initialization.
> @@ -5172,11 +6008,11 @@ int kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags, size_t size,
> slab_want_init_on_alloc(flags, s), s->object_size))) {
> return 0;
> }
> - return i;
> +
> + return size;
> }
> EXPORT_SYMBOL(kmem_cache_alloc_bulk_noprof);
>
> -
> /*
> * Object placement in a slab is made very easy because we always start at
> * offset 0. If we tune the size of the object to the alignment then we can
> @@ -5309,8 +6145,8 @@ static inline int calculate_order(unsigned int size)
> return -ENOSYS;
> }
>
> -static void
> -init_kmem_cache_node(struct kmem_cache_node *n)
> +static bool
> +init_kmem_cache_node(struct kmem_cache_node *n, struct node_barn *barn)
> {
> n->nr_partial = 0;
> spin_lock_init(&n->list_lock);
> @@ -5320,6 +6156,11 @@ init_kmem_cache_node(struct kmem_cache_node *n)
> atomic_long_set(&n->total_objects, 0);
> INIT_LIST_HEAD(&n->full);
> #endif
> + n->barn = barn;
> + if (barn)
> + barn_init(barn);
> +
> + return true;
> }
>
> #ifndef CONFIG_SLUB_TINY
> @@ -5350,6 +6191,30 @@ static inline int alloc_kmem_cache_cpus(struct kmem_cache *s)
> }
> #endif /* CONFIG_SLUB_TINY */
>
> +static int init_percpu_sheaves(struct kmem_cache *s)
> +{
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + struct slub_percpu_sheaves *pcs;
> + int nid;
> +
> + pcs = per_cpu_ptr(s->cpu_sheaves, cpu);
> +
> + localtry_lock_init(&pcs->lock);
> +
> + nid = cpu_to_mem(cpu);
> +
> + pcs->barn = get_node(s, nid)->barn;
> + pcs->main = alloc_empty_sheaf(s, GFP_KERNEL);
> +
> + if (!pcs->main)
> + return -ENOMEM;
> + }
> +
> + return 0;
> +}
> +
> static struct kmem_cache *kmem_cache_node;
>
> /*
> @@ -5385,7 +6250,7 @@ static void early_kmem_cache_node_alloc(int node)
> slab->freelist = get_freepointer(kmem_cache_node, n);
> slab->inuse = 1;
> kmem_cache_node->node[node] = n;
> - init_kmem_cache_node(n);
> + init_kmem_cache_node(n, NULL);
> inc_slabs_node(kmem_cache_node, node, slab->objects);
>
> /*
> @@ -5401,6 +6266,13 @@ static void free_kmem_cache_nodes(struct kmem_cache *s)
> struct kmem_cache_node *n;
>
> for_each_kmem_cache_node(s, node, n) {
> + if (n->barn) {
> + WARN_ON(n->barn->nr_full);
> + WARN_ON(n->barn->nr_empty);
> + kfree(n->barn);
> + n->barn = NULL;
> + }
> +
> s->node[node] = NULL;
> kmem_cache_free(kmem_cache_node, n);
> }
> @@ -5409,6 +6281,8 @@ static void free_kmem_cache_nodes(struct kmem_cache *s)
> void __kmem_cache_release(struct kmem_cache *s)
> {
> cache_random_seq_destroy(s);
> + if (s->cpu_sheaves)
> + pcs_destroy(s);
> #ifndef CONFIG_SLUB_TINY
> free_percpu(s->cpu_slab);
> #endif
> @@ -5421,20 +6295,27 @@ static int init_kmem_cache_nodes(struct kmem_cache *s)
>
> for_each_node_mask(node, slab_nodes) {
> struct kmem_cache_node *n;
> + struct node_barn *barn = NULL;
>
> if (slab_state == DOWN) {
> early_kmem_cache_node_alloc(node);
> continue;
> }
> +
> + if (s->cpu_sheaves) {
> + barn = kmalloc_node(sizeof(*barn), GFP_KERNEL, node);
> +
> + if (!barn)
> + return 0;
> + }
> +
> n = kmem_cache_alloc_node(kmem_cache_node,
> GFP_KERNEL, node);
> -
> - if (!n) {
> - free_kmem_cache_nodes(s);
> + if (!n)
> return 0;
> - }
>
> - init_kmem_cache_node(n);
> + init_kmem_cache_node(n, barn);
> +
> s->node[node] = n;
> }
> return 1;
> @@ -5690,6 +6571,8 @@ int __kmem_cache_shutdown(struct kmem_cache *s)
> flush_all_cpus_locked(s);
> /* Attempt to free all objects */
> for_each_kmem_cache_node(s, node, n) {
> + if (n->barn)
> + barn_shrink(s, n->barn);
> free_partial(s, n);
> if (n->nr_partial || node_nr_slabs(n))
> return 1;
> @@ -5893,6 +6776,9 @@ static int __kmem_cache_do_shrink(struct kmem_cache *s)
> for (i = 0; i < SHRINK_PROMOTE_MAX; i++)
> INIT_LIST_HEAD(promote + i);
>
> + if (n->barn)
> + barn_shrink(s, n->barn);
> +
> spin_lock_irqsave(&n->list_lock, flags);
>
> /*
> @@ -6005,12 +6891,24 @@ static int slab_mem_going_online_callback(void *arg)
> */
> mutex_lock(&slab_mutex);
> list_for_each_entry(s, &slab_caches, list) {
> + struct node_barn *barn = NULL;
> +
> /*
> * The structure may already exist if the node was previously
> * onlined and offlined.
> */
> if (get_node(s, nid))
> continue;
> +
> + if (s->cpu_sheaves) {
> + barn = kmalloc_node(sizeof(*barn), GFP_KERNEL, nid);
> +
> + if (!barn) {
> + ret = -ENOMEM;
> + goto out;
> + }
> + }
> +
> /*
> * XXX: kmem_cache_alloc_node will fallback to other nodes
> * since memory is not yet available from the node that
> @@ -6021,7 +6919,9 @@ static int slab_mem_going_online_callback(void *arg)
> ret = -ENOMEM;
> goto out;
> }
> - init_kmem_cache_node(n);
> +
> + init_kmem_cache_node(n, barn);
> +
> s->node[nid] = n;
> }
> /*
> @@ -6240,6 +7140,16 @@ int do_kmem_cache_create(struct kmem_cache *s, const char *name,
>
> set_cpu_partial(s);
>
> + if (args->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
> s->remote_node_defrag_ratio = 1000;
> #endif
> @@ -6256,6 +7166,12 @@ int do_kmem_cache_create(struct kmem_cache *s, const char *name,
> if (!alloc_kmem_cache_cpus(s))
> goto out;
>
> + if (s->cpu_sheaves) {
> + err = init_percpu_sheaves(s);
> + if (err)
> + goto out;
> + }
> +
> err = 0;
>
> /* Mutex is not taken during early boot */
> @@ -6277,7 +7193,6 @@ int do_kmem_cache_create(struct kmem_cache *s, const char *name,
> __kmem_cache_release(s);
> return err;
> }
> -
> #ifdef SLAB_SUPPORTS_SYSFS
> static int count_inuse(struct slab *slab)
> {
> @@ -7055,8 +7970,10 @@ static ssize_t text##_store(struct kmem_cache *s, \
> } \
> SLAB_ATTR(text); \
>
> +STAT_ATTR(ALLOC_PCS, alloc_cpu_sheaf);
> STAT_ATTR(ALLOC_FASTPATH, alloc_fastpath);
> STAT_ATTR(ALLOC_SLOWPATH, alloc_slowpath);
> +STAT_ATTR(FREE_PCS, free_cpu_sheaf);
> STAT_ATTR(FREE_FASTPATH, free_fastpath);
> STAT_ATTR(FREE_SLOWPATH, free_slowpath);
> STAT_ATTR(FREE_FROZEN, free_frozen);
> @@ -7081,6 +7998,12 @@ STAT_ATTR(CPU_PARTIAL_ALLOC, cpu_partial_alloc);
> STAT_ATTR(CPU_PARTIAL_FREE, cpu_partial_free);
> STAT_ATTR(CPU_PARTIAL_NODE, cpu_partial_node);
> STAT_ATTR(CPU_PARTIAL_DRAIN, cpu_partial_drain);
> +STAT_ATTR(SHEAF_FLUSH_MAIN, sheaf_flush_main);
> +STAT_ATTR(SHEAF_FLUSH_OTHER, sheaf_flush_other);
> +STAT_ATTR(SHEAF_REFILL, sheaf_refill);
> +STAT_ATTR(SHEAF_SWAP, sheaf_swap);
> +STAT_ATTR(SHEAF_ALLOC, sheaf_alloc);
> +STAT_ATTR(SHEAF_FREE, sheaf_free);
> #endif /* CONFIG_SLUB_STATS */
>
> #ifdef CONFIG_KFENCE
> @@ -7142,8 +8065,10 @@ static struct attribute *slab_attrs[] = {
> &remote_node_defrag_ratio_attr.attr,
> #endif
> #ifdef CONFIG_SLUB_STATS
> + &alloc_cpu_sheaf_attr.attr,
> &alloc_fastpath_attr.attr,
> &alloc_slowpath_attr.attr,
> + &free_cpu_sheaf_attr.attr,
> &free_fastpath_attr.attr,
> &free_slowpath_attr.attr,
> &free_frozen_attr.attr,
> @@ -7168,6 +8093,12 @@ static struct attribute *slab_attrs[] = {
> &cpu_partial_free_attr.attr,
> &cpu_partial_node_attr.attr,
> &cpu_partial_drain_attr.attr,
> + &sheaf_flush_main_attr.attr,
> + &sheaf_flush_other_attr.attr,
> + &sheaf_refill_attr.attr,
> + &sheaf_swap_attr.attr,
> + &sheaf_alloc_attr.attr,
> + &sheaf_free_attr.attr,
> #endif
> #ifdef CONFIG_FAILSLAB
> &failslab_attr.attr,
>
> --
> 2.48.1
>