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percpu: allow limited allocation before slab is online

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This patch updates percpu allocator such that it can serve limited
amount of allocation before slab comes online.  This is primarily to
allow slab to depend on working percpu allocator.

Two parameters, PERCPU_DYNAMIC_EARLY_SIZE and SLOTS, determine how
much memory space and allocation map slots are reserved.  If this
reserved area is exhausted, WARN_ON_ONCE() will trigger and allocation
will fail till slab comes online.

The following changes are made to implement early alloc.

* pcpu_mem_alloc() now checks slab_is_available()

* Chunks are allocated using pcpu_mem_alloc()

* Init paths make sure ai->dyn_size is at least as large as
  PERCPU_DYNAMIC_EARLY_SIZE.

* Initial alloc maps are allocated in __initdata and copied to
  kmalloc'd areas once slab is online.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
This commit is contained in:
Tejun Heo
2010-06-27 18:50:00 +02:00
parent 4ba6ce250e
commit 099a19d91c
3 changed files with 54 additions and 12 deletions
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13
include/linux/percpu.h
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@@ -44,6 +44,16 @@
/* minimum unit size, also is the maximum supported allocation size */
#define PCPU_MIN_UNIT_SIZE PFN_ALIGN(64 << 10)
/*
* Percpu allocator can serve percpu allocations before slab is
* initialized which allows slab to depend on the percpu allocator.
* The following two parameters decide how much resource to
* preallocate for this. Keep PERCPU_DYNAMIC_RESERVE equal to or
* larger than PERCPU_DYNAMIC_EARLY_SIZE.
*/
#define PERCPU_DYNAMIC_EARLY_SLOTS 128
#define PERCPU_DYNAMIC_EARLY_SIZE (12 << 10)
/*
* PERCPU_DYNAMIC_RESERVE indicates the amount of free area to piggy
* back on the first chunk for dynamic percpu allocation if arch is
@@ -135,6 +145,7 @@ extern bool is_kernel_percpu_address(unsigned long addr);
#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
extern void __init setup_per_cpu_areas(void);
#endif
extern void __init percpu_init_late(void);
#else /* CONFIG_SMP */
@@ -148,6 +159,8 @@ static inline bool is_kernel_percpu_address(unsigned long addr)
static inline void __init setup_per_cpu_areas(void) { }
static inline void __init percpu_init_late(void) { }
static inline void *pcpu_lpage_remapped(void *kaddr)
{
return NULL;