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Subject[PATCH 15/16] mm: Enable SLUB for RT
Date
From: Thomas Gleixner <tglx@linutronix.de>

Make SLUB RT aware and remove the restriction in Kconfig.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy@linutronix: fix a few conflicts]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/slub_def.h | 2 +-
init/Kconfig | 1 -
mm/slub.c | 115 +++++++++++++++++++++++++++++++++++-----------
3 files changed, 90 insertions(+), 28 deletions(-)

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index a32bcfd..0c674f6 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -52,7 +52,7 @@ struct kmem_cache_cpu {
};

struct kmem_cache_node {
- spinlock_t list_lock; /* Protect partial list and nr_partial */
+ raw_spinlock_t list_lock; /* Protect partial list and nr_partial */
unsigned long nr_partial;
struct list_head partial;
#ifdef CONFIG_SLUB_DEBUG
diff --git a/init/Kconfig b/init/Kconfig
index aa6545f..cfb1668 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1240,7 +1240,6 @@ config SLAB

config SLUB
bool "SLUB (Unqueued Allocator)"
- depends on !PREEMPT_RT_FULL
help
SLUB is a slab allocator that minimizes cache line usage
instead of managing queues of cached objects (SLAB approach).
diff --git a/mm/slub.c b/mm/slub.c
index 2a250f4..8475580 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1258,6 +1258,12 @@ static inline void slab_free_hook(struct kmem_cache *s, void *x) {}

#endif /* CONFIG_SLUB_DEBUG */

+struct slub_free_list {
+ raw_spinlock_t lock;
+ struct list_head list;
+};
+static DEFINE_PER_CPU(struct slub_free_list, slub_free_list);
+
/*
* Slab allocation and freeing
*/
@@ -1282,7 +1288,11 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)

flags &= gfp_allowed_mask;

+#ifdef CONFIG_PREEMPT_RT_FULL
+ if (system_state == SYSTEM_RUNNING)
+#else
if (flags & __GFP_WAIT)
+#endif
local_irq_enable();

flags |= s->allocflags;
@@ -1306,7 +1316,11 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
stat(s, ORDER_FALLBACK);
}

+#ifdef CONFIG_PREEMPT_RT_FULL
+ if (system_state == SYSTEM_RUNNING)
+#else
if (flags & __GFP_WAIT)
+#endif
local_irq_disable();

if (!page)
@@ -1412,6 +1426,16 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
__free_pages(page, order);
}

+static void free_delayed(struct kmem_cache *s, struct list_head *h)
+{
+ while(!list_empty(h)) {
+ struct page *page = list_first_entry(h, struct page, lru);
+
+ list_del(&page->lru);
+ __free_slab(s, page);
+ }
+}
+
#define need_reserve_slab_rcu \
(sizeof(((struct page *)NULL)->lru) < sizeof(struct rcu_head))

@@ -1446,6 +1470,12 @@ static void free_slab(struct kmem_cache *s, struct page *page)
}

call_rcu(head, rcu_free_slab);
+ } else if (irqs_disabled()) {
+ struct slub_free_list *f = &__get_cpu_var(slub_free_list);
+
+ raw_spin_lock(&f->lock);
+ list_add(&page->lru, &f->list);
+ raw_spin_unlock(&f->lock);
} else
__free_slab(s, page);
}
@@ -1545,7 +1575,7 @@ static void *get_partial_node(struct kmem_cache *s,
if (!n || !n->nr_partial)
return NULL;

- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
list_for_each_entry_safe(page, page2, &n->partial, lru) {
void *t = acquire_slab(s, n, page, object == NULL);
int available;
@@ -1566,7 +1596,7 @@ static void *get_partial_node(struct kmem_cache *s,
break;

}
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);
return object;
}

@@ -1815,7 +1845,7 @@ static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
* that acquire_slab() will see a slab page that
* is frozen
*/
- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
}
} else {
m = M_FULL;
@@ -1826,7 +1856,7 @@ static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
* slabs from diagnostic functions will not see
* any frozen slabs.
*/
- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
}
}

@@ -1861,7 +1891,7 @@ static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
goto redo;

if (lock)
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);

if (m == M_FREE) {
stat(s, DEACTIVATE_EMPTY);
@@ -1910,10 +1940,10 @@ static void unfreeze_partials(struct kmem_cache *s,
m = M_PARTIAL;
if (n != n2) {
if (n)
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);

n = n2;
- spin_lock(&n->list_lock);
+ raw_spin_lock(&n->list_lock);
}
}

@@ -1939,7 +1969,7 @@ static void unfreeze_partials(struct kmem_cache *s,
}

if (n)
- spin_unlock(&n->list_lock);
+ raw_spin_unlock(&n->list_lock);

while (discard_page) {
page = discard_page;
@@ -1960,7 +1990,7 @@ static void unfreeze_partials(struct kmem_cache *s,
* If we did not find a slot then simply move all the partials to the
* per node partial list.
*/
-int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
+static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
{
struct page *oldpage;
int pages;
@@ -1975,6 +2005,8 @@ int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
pobjects = oldpage->pobjects;
pages = oldpage->pages;
if (drain && pobjects > s->cpu_partial) {
+ LIST_HEAD(tofree);
+ struct slub_free_list *f;
unsigned long flags;
/*
* partial array is full. Move the existing
@@ -1982,7 +2014,12 @@ int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
*/
local_irq_save(flags);
unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
+ f = &__get_cpu_var(slub_free_list);
+ raw_spin_lock(&f->lock);
+ list_splice_init(&f->list, &tofree);
+ raw_spin_unlock(&f->lock);
local_irq_restore(flags);
+ free_delayed(s, &tofree);
pobjects = 0;
pages = 0;
}
@@ -2040,7 +2077,22 @@ static bool has_cpu_slab(int cpu, void *info)

static void flush_all(struct kmem_cache *s)
{
+ LIST_HEAD(tofree);
+ int cpu;
+
on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1, GFP_ATOMIC);
+ for_each_online_cpu(cpu) {
+ struct slub_free_list *f;
+
+ if (!has_cpu_slab(cpu, s))
+ continue;
+
+ f = &per_cpu(slub_free_list, cpu);
+ raw_spin_lock_irq(&f->lock);
+ list_splice_init(&f->list, &tofree);
+ raw_spin_unlock_irq(&f->lock);
+ free_delayed(s, &tofree);
+ }
}

/*
@@ -2068,10 +2120,10 @@ static unsigned long count_partial(struct kmem_cache_node *n,
unsigned long x = 0;
struct page *page;

- spin_lock_irqsave(&n->list_lock, flags);
+ raw_spin_lock_irqsave(&n->list_lock, flags);
list_for_each_entry(page, &n->partial, lru)
x += get_count(page);
- spin_unlock_irqrestore(&n->list_lock, flags);
+ raw_spin_unlock_irqrestore(&n->list_lock, flags);
return x;
}

@@ -2167,6 +2219,8 @@ static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags,
static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
unsigned long addr, struct kmem_cache_cpu *c)
{
+ struct slub_free_list *f;
+ LIST_HEAD(tofree);
void **object;
unsigned long flags;
struct page new;
@@ -2233,7 +2287,13 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
load_freelist:
c->freelist = get_freepointer(s, object);
c->tid = next_tid(c->tid);
+out:
+ f = &__get_cpu_var(slub_free_list);
+ raw_spin_lock(&f->lock);
+ list_splice_init(&f->list, &tofree);
+ raw_spin_unlock(&f->lock);
local_irq_restore(flags);
+ free_delayed(s, &tofree);
return object;

new_slab:
@@ -2258,8 +2318,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
if (!(gfpflags & __GFP_NOWARN) && printk_ratelimit())
slab_out_of_memory(s, gfpflags, node);

- local_irq_restore(flags);
- return NULL;
+ goto out;
}
}

@@ -2273,8 +2332,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
c->freelist = get_freepointer(s, object);
deactivate_slab(s, c);
c->node = NUMA_NO_NODE;
- local_irq_restore(flags);
- return object;
+ goto out;
}

/*
@@ -2466,7 +2524,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
* Otherwise the list_lock will synchronize with
* other processors updating the list of slabs.
*/
- spin_lock_irqsave(&n->list_lock, flags);
+ raw_spin_lock_irqsave(&n->list_lock, flags);

}
}
@@ -2515,7 +2573,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
stat(s, FREE_ADD_PARTIAL);
}
}
- spin_unlock_irqrestore(&n->list_lock, flags);
+ raw_spin_unlock_irqrestore(&n->list_lock, flags);
return;

slab_empty:
@@ -2529,7 +2587,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
/* Slab must be on the full list */
remove_full(s, page);

- spin_unlock_irqrestore(&n->list_lock, flags);
+ raw_spin_unlock_irqrestore(&n->list_lock, flags);
stat(s, FREE_SLAB);
discard_slab(s, page);
}
@@ -2759,7 +2817,7 @@ static void
init_kmem_cache_node(struct kmem_cache_node *n, struct kmem_cache *s)
{
n->nr_partial = 0;
- spin_lock_init(&n->list_lock);
+ raw_spin_lock_init(&n->list_lock);
INIT_LIST_HEAD(&n->partial);
#ifdef CONFIG_SLUB_DEBUG
atomic_long_set(&n->nr_slabs, 0);
@@ -3499,7 +3557,7 @@ int kmem_cache_shrink(struct kmem_cache *s)
for (i = 0; i < objects; i++)
INIT_LIST_HEAD(slabs_by_inuse + i);

- spin_lock_irqsave(&n->list_lock, flags);
+ raw_spin_lock_irqsave(&n->list_lock, flags);

/*
* Build lists indexed by the items in use in each slab.
@@ -3520,7 +3578,7 @@ int kmem_cache_shrink(struct kmem_cache *s)
for (i = objects - 1; i > 0; i--)
list_splice(slabs_by_inuse + i, n->partial.prev);

- spin_unlock_irqrestore(&n->list_lock, flags);
+ raw_spin_unlock_irqrestore(&n->list_lock, flags);

/* Release empty slabs */
list_for_each_entry_safe(page, t, slabs_by_inuse, lru)
@@ -3686,10 +3744,15 @@ void __init kmem_cache_init(void)
int i;
int caches = 0;
struct kmem_cache *temp_kmem_cache;
- int order;
+ int order, cpu;
struct kmem_cache *temp_kmem_cache_node;
unsigned long kmalloc_size;

+ for_each_possible_cpu(cpu) {
+ raw_spin_lock_init(&per_cpu(slub_free_list, cpu).lock);
+ INIT_LIST_HEAD(&per_cpu(slub_free_list, cpu).list);
+ }
+
kmem_size = offsetof(struct kmem_cache, node) +
nr_node_ids * sizeof(struct kmem_cache_node *);

@@ -4110,7 +4173,7 @@ static int validate_slab_node(struct kmem_cache *s,
struct page *page;
unsigned long flags;

- spin_lock_irqsave(&n->list_lock, flags);
+ raw_spin_lock_irqsave(&n->list_lock, flags);

list_for_each_entry(page, &n->partial, lru) {
validate_slab_slab(s, page, map);
@@ -4133,7 +4196,7 @@ static int validate_slab_node(struct kmem_cache *s,
atomic_long_read(&n->nr_slabs));

out:
- spin_unlock_irqrestore(&n->list_lock, flags);
+ raw_spin_unlock_irqrestore(&n->list_lock, flags);
return count;
}

@@ -4323,12 +4386,12 @@ static int list_locations(struct kmem_cache *s, char *buf,
if (!atomic_long_read(&n->nr_slabs))
continue;

- spin_lock_irqsave(&n->list_lock, flags);
+ raw_spin_lock_irqsave(&n->list_lock, flags);
list_for_each_entry(page, &n->partial, lru)
process_slab(&t, s, page, alloc, map);
list_for_each_entry(page, &n->full, lru)
process_slab(&t, s, page, alloc, map);
- spin_unlock_irqrestore(&n->list_lock, flags);
+ raw_spin_unlock_irqrestore(&n->list_lock, flags);
}

for (i = 0; i < t.count; i++) {
--
1.7.10.4


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