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Diffstat (limited to 'mm/percpu.c')
-rw-r--r--mm/percpu.c117
1 files changed, 113 insertions, 4 deletions
diff --git a/mm/percpu.c b/mm/percpu.c
index 28a830590b4c..867efd38d879 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -78,6 +78,8 @@
#define PCPU_DFL_MAP_ALLOC 16 /* start a map with 16 ents */
#define PCPU_ATOMIC_MAP_MARGIN_LOW 32
#define PCPU_ATOMIC_MAP_MARGIN_HIGH 64
+#define PCPU_EMPTY_POP_PAGES_LOW 2
+#define PCPU_EMPTY_POP_PAGES_HIGH 4
#ifdef CONFIG_SMP
/* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
@@ -168,9 +170,22 @@ static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
*/
static int pcpu_nr_empty_pop_pages;
-/* balance work is used to populate or destroy chunks asynchronously */
+/*
+ * Balance work is used to populate or destroy chunks asynchronously. We
+ * try to keep the number of populated free pages between
+ * PCPU_EMPTY_POP_PAGES_LOW and HIGH for atomic allocations and at most one
+ * empty chunk.
+ */
static void pcpu_balance_workfn(struct work_struct *work);
static DECLARE_WORK(pcpu_balance_work, pcpu_balance_workfn);
+static bool pcpu_async_enabled __read_mostly;
+static bool pcpu_atomic_alloc_failed;
+
+static void pcpu_schedule_balance_work(void)
+{
+ if (pcpu_async_enabled)
+ schedule_work(&pcpu_balance_work);
+}
static bool pcpu_addr_in_first_chunk(void *addr)
{
@@ -386,7 +401,8 @@ static int pcpu_need_to_extend(struct pcpu_chunk *chunk, bool is_atomic)
margin = 3;
if (chunk->map_alloc <
- chunk->map_used + PCPU_ATOMIC_MAP_MARGIN_LOW)
+ chunk->map_used + PCPU_ATOMIC_MAP_MARGIN_LOW &&
+ pcpu_async_enabled)
schedule_work(&chunk->map_extend_work);
} else {
margin = PCPU_ATOMIC_MAP_MARGIN_HIGH;
@@ -1005,6 +1021,9 @@ area_found:
if (chunk != pcpu_reserved_chunk)
pcpu_nr_empty_pop_pages -= occ_pages;
+ if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
+ pcpu_schedule_balance_work();
+
/* clear the areas and return address relative to base address */
for_each_possible_cpu(cpu)
memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
@@ -1023,6 +1042,11 @@ fail:
if (!--warn_limit)
pr_info("PERCPU: limit reached, disable warning\n");
}
+ if (is_atomic) {
+ /* see the flag handling in pcpu_blance_workfn() */
+ pcpu_atomic_alloc_failed = true;
+ pcpu_schedule_balance_work();
+ }
return NULL;
}
@@ -1080,7 +1104,7 @@ void __percpu *__alloc_reserved_percpu(size_t size, size_t align)
}
/**
- * pcpu_balance_workfn - reclaim fully free chunks, workqueue function
+ * pcpu_balance_workfn - manage the amount of free chunks and populated pages
* @work: unused
*
* Reclaim all fully free chunks except for the first one.
@@ -1090,7 +1114,12 @@ static void pcpu_balance_workfn(struct work_struct *work)
LIST_HEAD(to_free);
struct list_head *free_head = &pcpu_slot[pcpu_nr_slots - 1];
struct pcpu_chunk *chunk, *next;
+ int slot, nr_to_pop, ret;
+ /*
+ * There's no reason to keep around multiple unused chunks and VM
+ * areas can be scarce. Destroy all free chunks except for one.
+ */
mutex_lock(&pcpu_alloc_mutex);
spin_lock_irq(&pcpu_lock);
@@ -1118,6 +1147,74 @@ static void pcpu_balance_workfn(struct work_struct *work)
pcpu_destroy_chunk(chunk);
}
+ /*
+ * Ensure there are certain number of free populated pages for
+ * atomic allocs. Fill up from the most packed so that atomic
+ * allocs don't increase fragmentation. If atomic allocation
+ * failed previously, always populate the maximum amount. This
+ * should prevent atomic allocs larger than PAGE_SIZE from keeping
+ * failing indefinitely; however, large atomic allocs are not
+ * something we support properly and can be highly unreliable and
+ * inefficient.
+ */
+retry_pop:
+ if (pcpu_atomic_alloc_failed) {
+ nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH;
+ /* best effort anyway, don't worry about synchronization */
+ pcpu_atomic_alloc_failed = false;
+ } else {
+ nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH -
+ pcpu_nr_empty_pop_pages,
+ 0, PCPU_EMPTY_POP_PAGES_HIGH);
+ }
+
+ for (slot = pcpu_size_to_slot(PAGE_SIZE); slot < pcpu_nr_slots; slot++) {
+ int nr_unpop = 0, rs, re;
+
+ if (!nr_to_pop)
+ break;
+
+ spin_lock_irq(&pcpu_lock);
+ list_for_each_entry(chunk, &pcpu_slot[slot], list) {
+ nr_unpop = pcpu_unit_pages - chunk->nr_populated;
+ if (nr_unpop)
+ break;
+ }
+ spin_unlock_irq(&pcpu_lock);
+
+ if (!nr_unpop)
+ continue;
+
+ /* @chunk can't go away while pcpu_alloc_mutex is held */
+ pcpu_for_each_unpop_region(chunk, rs, re, 0, pcpu_unit_pages) {
+ int nr = min(re - rs, nr_to_pop);
+
+ ret = pcpu_populate_chunk(chunk, rs, rs + nr);
+ if (!ret) {
+ nr_to_pop -= nr;
+ spin_lock_irq(&pcpu_lock);
+ pcpu_chunk_populated(chunk, rs, rs + nr);
+ spin_unlock_irq(&pcpu_lock);
+ } else {
+ nr_to_pop = 0;
+ }
+
+ if (!nr_to_pop)
+ break;
+ }
+ }
+
+ if (nr_to_pop) {
+ /* ran out of chunks to populate, create a new one and retry */
+ chunk = pcpu_create_chunk();
+ if (chunk) {
+ spin_lock_irq(&pcpu_lock);
+ pcpu_chunk_relocate(chunk, -1);
+ spin_unlock_irq(&pcpu_lock);
+ goto retry_pop;
+ }
+ }
+
mutex_unlock(&pcpu_alloc_mutex);
}
@@ -1160,7 +1257,7 @@ void free_percpu(void __percpu *ptr)
list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list)
if (pos != chunk) {
- schedule_work(&pcpu_balance_work);
+ pcpu_schedule_balance_work();
break;
}
}
@@ -2187,3 +2284,15 @@ void __init percpu_init_late(void)
spin_unlock_irqrestore(&pcpu_lock, flags);
}
}
+
+/*
+ * Percpu allocator is initialized early during boot when neither slab or
+ * workqueue is available. Plug async management until everything is up
+ * and running.
+ */
+static int __init percpu_enable_async(void)
+{
+ pcpu_async_enabled = true;
+ return 0;
+}
+subsys_initcall(percpu_enable_async);