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percpu: allow non-linear / sparse cpu -> unit mapping

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Currently cpu and unit are always identity mapped.  To allow more
efficient large page support on NUMA and lazy allocation for possible
but offline cpus, cpu -> unit mapping needs to be non-linear and/or
sparse.  This can be easily implemented by adding a cpu -> unit
mapping array and using it whenever looking up the matching unit for a
cpu.

The only unusal conversion is in pcpu_chunk_addr_search().  The passed
in address is unit0 based and unit0 might not be in use so it needs to
be converted to address of an in-use unit.  This is easily done by
adding the unit offset for the current processor.

[ Impact: allows non-linear/sparse cpu -> unit mapping, no visible change yet ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
This commit is contained in:
Tejun Heo 2009-07-04 08:11:00 +09:00
commit 2f39e637ea
3 changed files with 97 additions and 37 deletions
Download patch file Download diff file Expand all files Collapse all files

2
arch/sparc/kernel/smp_64.c
View file

@ -1516,7 +1516,7 @@ void __init setup_per_cpu_areas(void)
pcpu_unit_size = pcpu_setup_first_chunk(static_size,
PERCPU_MODULE_RESERVE, dyn_size,
PCPU_CHUNK_SIZE, vm.addr);
PCPU_CHUNK_SIZE, vm.addr, NULL);
free_bootmem(__pa(ptrs), ptrs_size);

3
include/linux/percpu.h
View file

@ -57,6 +57,7 @@
#endif
extern void *pcpu_base_addr;
extern const int *pcpu_unit_map;
typedef void * (*pcpu_fc_alloc_fn_t)(unsigned int cpu, size_t size);
typedef void (*pcpu_fc_free_fn_t)(void *ptr, size_t size);
@ -66,7 +67,7 @@ typedef void (*pcpu_fc_map_fn_t)(void *ptr, size_t size, void *addr);
extern size_t __init pcpu_setup_first_chunk(
size_t static_size, size_t reserved_size,
ssize_t dyn_size, size_t unit_size,
void *base_addr);
void *base_addr, const int *unit_map);
extern ssize_t __init pcpu_embed_first_chunk(
size_t static_size, size_t reserved_size,

129
mm/percpu.c
View file

@ -8,12 +8,13 @@
*
* This is percpu allocator which can handle both static and dynamic
* areas. Percpu areas are allocated in chunks in vmalloc area. Each
* chunk is consisted of num_possible_cpus() units and the first chunk
* is used for static percpu variables in the kernel image (special
* boot time alloc/init handling necessary as these areas need to be
* brought up before allocation services are running). Unit grows as
* necessary and all units grow or shrink in unison. When a chunk is
* filled up, another chunk is allocated. ie. in vmalloc area
* chunk is consisted of boot-time determined number of units and the
* first chunk is used for static percpu variables in the kernel image
* (special boot time alloc/init handling necessary as these areas
* need to be brought up before allocation services are running).
* Unit grows as necessary and all units grow or shrink in unison.
* When a chunk is filled up, another chunk is allocated. ie. in
* vmalloc area
*
* c0 c1 c2
* ------------------- ------------------- ------------
@ -22,11 +23,13 @@
*
* Allocation is done in offset-size areas of single unit space. Ie,
* an area of 512 bytes at 6k in c1 occupies 512 bytes at 6k of c1:u0,
* c1:u1, c1:u2 and c1:u3. Percpu access can be done by configuring
* percpu base registers pcpu_unit_size apart.
* c1:u1, c1:u2 and c1:u3. On UMA, units corresponds directly to
* cpus. On NUMA, the mapping can be non-linear and even sparse.
* Percpu access can be done by configuring percpu base registers
* according to cpu to unit mapping and pcpu_unit_size.
*
* There are usually many small percpu allocations many of them as
* small as 4 bytes. The allocator organizes chunks into lists
* There are usually many small percpu allocations many of them being
* as small as 4 bytes. The allocator organizes chunks into lists
* according to free size and tries to allocate from the fullest one.
* Each chunk keeps the maximum contiguous area size hint which is
* guaranteed to be eqaul to or larger than the maximum contiguous
@ -99,14 +102,22 @@ struct pcpu_chunk {
static int pcpu_unit_pages __read_mostly;
static int pcpu_unit_size __read_mostly;
static int pcpu_nr_units __read_mostly;
static int pcpu_chunk_size __read_mostly;
static int pcpu_nr_slots __read_mostly;
static size_t pcpu_chunk_struct_size __read_mostly;
/* cpus with the lowest and highest unit numbers */
static unsigned int pcpu_first_unit_cpu __read_mostly;
static unsigned int pcpu_last_unit_cpu __read_mostly;
/* the address of the first chunk which starts with the kernel static area */
void *pcpu_base_addr __read_mostly;
EXPORT_SYMBOL_GPL(pcpu_base_addr);
/* cpu -> unit map */
const int *pcpu_unit_map __read_mostly;
/*
* The first chunk which always exists. Note that unlike other
* chunks, this one can be allocated and mapped in several different
@ -177,7 +188,7 @@ static int pcpu_chunk_slot(const struct pcpu_chunk *chunk)
static int pcpu_page_idx(unsigned int cpu, int page_idx)
{
return cpu * pcpu_unit_pages + page_idx;
return pcpu_unit_map[cpu] * pcpu_unit_pages + page_idx;
}
static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
@ -321,6 +332,14 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
return pcpu_first_chunk;
}
/*
* The address is relative to unit0 which might be unused and
* thus unmapped. Offset the address to the unit space of the
* current processor before looking it up in the vmalloc
* space. Note that any possible cpu id can be used here, so
* there's no need to worry about preemption or cpu hotplug.
*/
addr += pcpu_unit_map[smp_processor_id()] * pcpu_unit_size;
return pcpu_get_page_chunk(vmalloc_to_page(addr));
}
@ -593,8 +612,7 @@ static struct page **pcpu_get_pages_and_bitmap(struct pcpu_chunk *chunk,
{
static struct page **pages;
static unsigned long *bitmap;
size_t pages_size = num_possible_cpus() * pcpu_unit_pages *
sizeof(pages[0]);
size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);
size_t bitmap_size = BITS_TO_LONGS(pcpu_unit_pages) *
sizeof(unsigned long);
@ -692,10 +710,9 @@ static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
static void pcpu_pre_unmap_flush(struct pcpu_chunk *chunk,
int page_start, int page_end)
{
unsigned int last = num_possible_cpus() - 1;
flush_cache_vunmap(pcpu_chunk_addr(chunk, 0, page_start),
pcpu_chunk_addr(chunk, last, page_end));
flush_cache_vunmap(
pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
}
static void __pcpu_unmap_pages(unsigned long addr, int nr_pages)
@ -756,10 +773,9 @@ static void pcpu_unmap_pages(struct pcpu_chunk *chunk,
static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
int page_start, int page_end)
{
unsigned int last = num_possible_cpus() - 1;
flush_tlb_kernel_range(pcpu_chunk_addr(chunk, 0, page_start),
pcpu_chunk_addr(chunk, last, page_end));
flush_tlb_kernel_range(
pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
}
static int __pcpu_map_pages(unsigned long addr, struct page **pages,
@ -835,11 +851,9 @@ err:
static void pcpu_post_map_flush(struct pcpu_chunk *chunk,
int page_start, int page_end)
{
unsigned int last = num_possible_cpus() - 1;
/* flush at once, please read comments in pcpu_unmap() */
flush_cache_vmap(pcpu_chunk_addr(chunk, 0, page_start),
pcpu_chunk_addr(chunk, last, page_end));
flush_cache_vmap(
pcpu_chunk_addr(chunk, pcpu_first_unit_cpu, page_start),
pcpu_chunk_addr(chunk, pcpu_last_unit_cpu, page_end));
}
/**
@ -953,8 +967,7 @@ static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
clear:
for_each_possible_cpu(cpu)
memset(chunk->vm->addr + cpu * pcpu_unit_size + off, 0,
size);
memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
return 0;
err_unmap:
@ -1088,6 +1101,7 @@ area_found:
mutex_unlock(&pcpu_alloc_mutex);
/* return address relative to unit0 */
return __addr_to_pcpu_ptr(chunk->vm->addr + off);
fail_unlock:
@ -1222,6 +1236,7 @@ EXPORT_SYMBOL_GPL(free_percpu);
* @dyn_size: free size for dynamic allocation in bytes, -1 for auto
* @unit_size: unit size in bytes, must be multiple of PAGE_SIZE
* @base_addr: mapped address
* @unit_map: cpu -> unit map, NULL for sequential mapping
*
* Initialize the first percpu chunk which contains the kernel static
* perpcu area. This function is to be called from arch percpu area
@ -1260,16 +1275,17 @@ EXPORT_SYMBOL_GPL(free_percpu);
*/
size_t __init pcpu_setup_first_chunk(size_t static_size, size_t reserved_size,
ssize_t dyn_size, size_t unit_size,
void *base_addr)
void *base_addr, const int *unit_map)
{
static struct vm_struct first_vm;
static int smap[2], dmap[2];
size_t size_sum = static_size + reserved_size +
(dyn_size >= 0 ? dyn_size : 0);
struct pcpu_chunk *schunk, *dchunk = NULL;
unsigned int cpu, tcpu;
int i;
/* santiy checks */
/* sanity checks */
BUILD_BUG_ON(ARRAY_SIZE(smap) >= PCPU_DFL_MAP_ALLOC ||
ARRAY_SIZE(dmap) >= PCPU_DFL_MAP_ALLOC);
BUG_ON(!static_size);
@ -1278,9 +1294,52 @@ size_t __init pcpu_setup_first_chunk(size_t static_size, size_t reserved_size,
BUG_ON(unit_size & ~PAGE_MASK);
BUG_ON(unit_size < PCPU_MIN_UNIT_SIZE);
/* determine number of units and verify and initialize pcpu_unit_map */
if (unit_map) {
int first_unit = INT_MAX, last_unit = INT_MIN;
for_each_possible_cpu(cpu) {
int unit = unit_map[cpu];
BUG_ON(unit < 0);
for_each_possible_cpu(tcpu) {
if (tcpu == cpu)
break;
/* the mapping should be one-to-one */
BUG_ON(unit_map[tcpu] == unit);
}
if (unit < first_unit) {
pcpu_first_unit_cpu = cpu;
first_unit = unit;
}
if (unit > last_unit) {
pcpu_last_unit_cpu = cpu;
last_unit = unit;
}
}
pcpu_nr_units = last_unit + 1;
pcpu_unit_map = unit_map;
} else {
int *identity_map;
/* #units == #cpus, identity mapped */
identity_map = alloc_bootmem(num_possible_cpus() *
sizeof(identity_map[0]));
for_each_possible_cpu(cpu)
identity_map[cpu] = cpu;
pcpu_first_unit_cpu = 0;
pcpu_last_unit_cpu = pcpu_nr_units - 1;
pcpu_nr_units = num_possible_cpus();
pcpu_unit_map = identity_map;
}
/* determine basic parameters */
pcpu_unit_pages = unit_size >> PAGE_SHIFT;
pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
pcpu_chunk_size = pcpu_nr_units * pcpu_unit_size;
pcpu_chunk_struct_size = sizeof(struct pcpu_chunk) +
BITS_TO_LONGS(pcpu_unit_pages) * sizeof(unsigned long);
@ -1349,7 +1408,7 @@ size_t __init pcpu_setup_first_chunk(size_t static_size, size_t reserved_size,
pcpu_chunk_relocate(pcpu_first_chunk, -1);
/* we're done */
pcpu_base_addr = (void *)pcpu_chunk_addr(schunk, 0, 0);
pcpu_base_addr = schunk->vm->addr;
return pcpu_unit_size;
}
@ -1427,7 +1486,7 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
size_sum >> PAGE_SHIFT, base, static_size);
return pcpu_setup_first_chunk(static_size, reserved_size, dyn_size,
unit_size, base);
unit_size, base, NULL);
}
/**
@ -1519,7 +1578,7 @@ ssize_t __init pcpu_4k_first_chunk(size_t static_size, size_t reserved_size,
unit_pages, static_size);
ret = pcpu_setup_first_chunk(static_size, reserved_size, -1,
unit_pages << PAGE_SHIFT, vm.addr);
unit_pages << PAGE_SHIFT, vm.addr, NULL);
goto out_free_ar;
enomem:
@ -1641,7 +1700,7 @@ ssize_t __init pcpu_lpage_first_chunk(size_t static_size, size_t reserved_size,
"%zu bytes\n", pcpul_vm.addr, static_size);
ret = pcpu_setup_first_chunk(static_size, reserved_size, dyn_size,
pcpul_unit_size, pcpul_vm.addr);
pcpul_unit_size, pcpul_vm.addr, NULL);
/* sort pcpul_map array for pcpu_lpage_remapped() */
for (i = 0; i < num_possible_cpus() - 1; i++)