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Subject[rfc 34/45] x86_64: Fold percpu area into the cpu area.
Use boot_cpu_alloc to allocate a cpu area chunk that is needed to store the
statically declared per cpu data and then point the per_cpu_offset pointers
to the cpu area.

The per cpu area is moved to a ZERO offset using some linker scripting.
All per cpu variable addresses become true offsets into a cpu area to their
respective variable. The addresses of per cpu variables can be treated
like the offsets that are returned by CPU_ALLOC.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
arch/x86/kernel/setup64.c | 29 ++++++++++++-----------------
arch/x86/kernel/vmlinux_64.lds.S | 3 ++-
include/asm-generic/sections.h | 1 +
include/asm-generic/vmlinux.lds.h | 17 +++++++++++++++++
4 files changed, 32 insertions(+), 18 deletions(-)

Index: linux-2.6/arch/x86/kernel/setup64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup64.c 2007-11-18 22:39:24.706247819 -0800
+++ linux-2.6/arch/x86/kernel/setup64.c 2007-11-19 10:31:49.088824106 -0800
@@ -87,35 +87,30 @@ __setup("noexec32=", nonx32_setup);
void __init setup_per_cpu_areas(void)
{
int i;
- unsigned long size;
+ char *base;

#ifdef CONFIG_HOTPLUG_CPU
prefill_possible_map();
#endif

/* Copy section for each CPU (we discard the original) */
- size = PERCPU_ENOUGH_ROOM;
+ base = boot_cpu_alloc(PERCPU_ENOUGH_ROOM);
+ if (base)
+ panic("Cannot allocate per cpu data at 0\n");

- printk(KERN_INFO "PERCPU: Allocating %lu bytes of per cpu data\n", size);
+ printk(KERN_INFO "PERCPU: Allocating %lu bytes of per cpu data\n",
+ PERCPU_ENOUGH_ROOM);
for_each_cpu_mask (i, cpu_possible_map) {
- char *ptr;
+ cpu_pda(i)->data_offset = cpu_offset(i);

- if (!NODE_DATA(cpu_to_node(i))) {
- printk("cpu with no node %d, num_online_nodes %d\n",
- i, num_online_nodes());
- ptr = alloc_bootmem_pages(size);
- } else {
- ptr = alloc_bootmem_pages_node(NODE_DATA(cpu_to_node(i)), size);
- }
- if (!ptr)
- panic("Cannot allocate cpu data for CPU %d\n", i);
- cpu_pda(i)->data_offset = ptr - __per_cpu_start;
- memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
+ memcpy(CPU_PTR(base, i), __load_per_cpu_start,
+ __per_cpu_end - __per_cpu_start);
}
-}
+ count_vm_events(CPU_BYTES, PERCPU_ENOUGH_ROOM);
+}

void pda_init(int cpu)
-{
+{
struct x8664_pda *pda = cpu_pda(cpu);

/* Setup up data that may be needed in __get_free_pages early */
Index: linux-2.6/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux-2.6.orig/include/asm-generic/vmlinux.lds.h 2007-11-18 22:39:23.370497641 -0800
+++ linux-2.6/include/asm-generic/vmlinux.lds.h 2007-11-19 10:30:20.095586336 -0800
@@ -258,8 +258,25 @@
#define PERCPU(align) \
. = ALIGN(align); \
__per_cpu_start = .; \
+ __load_per_cpu_start = .; \
.data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { \
*(.data.percpu) \
*(.data.percpu.shared_aligned) \
} \
+ __load_per_cpu_end = .; \
__per_cpu_end = .;
+
+#define ZERO_BASED_PERCPU \
+ percpu : { } :percpu \
+ __load_per_cpu_start = .; \
+ .data.percpu 0 : AT(__load_per_cpu_start - LOAD_OFFSET) { \
+ __per_cpu_start = .; \
+ *(.data.percpu) \
+ *(.data.percpu.shared_aligned) \
+ __per_cpu_end = .; \
+ } \
+ . = __load_per_cpu_start + __per_cpu_end - __per_cpu_start; \
+ __load_per_cpu_end = .; \
+ data : { } :data
+
+
Index: linux-2.6/arch/x86/kernel/vmlinux_64.lds.S
===================================================================
--- linux-2.6.orig/arch/x86/kernel/vmlinux_64.lds.S 2007-11-18 22:41:39.261997209 -0800
+++ linux-2.6/arch/x86/kernel/vmlinux_64.lds.S 2007-11-18 22:42:33.119247430 -0800
@@ -19,6 +19,7 @@ cpu_area = CPU_AREA_BASE;

PHDRS {
text PT_LOAD FLAGS(5); /* R_E */
+ percpu PT_LOAD FLAGS(4); /* R__ */
data PT_LOAD FLAGS(7); /* RWE */
user PT_LOAD FLAGS(7); /* RWE */
data.init PT_LOAD FLAGS(7); /* RWE */
@@ -206,7 +207,7 @@ SECTIONS
__initramfs_end = .;
#endif

- PERCPU(4096)
+ ZERO_BASED_PERCPU

. = ALIGN(4096);
__init_end = .;
Index: linux-2.6/include/asm-generic/sections.h
===================================================================
--- linux-2.6.orig/include/asm-generic/sections.h 2007-11-18 22:39:23.374497627 -0800
+++ linux-2.6/include/asm-generic/sections.h 2007-11-18 22:45:33.073997351 -0800
@@ -12,6 +12,7 @@ extern char _sextratext[] __attribute__(
extern char _eextratext[] __attribute__((weak));
extern char _end[];
extern char __per_cpu_start[], __per_cpu_end[];
+extern char __load_per_cpu_start[], __load_per_cpu_end[];
extern char __kprobes_text_start[], __kprobes_text_end[];
extern char __initdata_begin[], __initdata_end[];
extern char __start_rodata[], __end_rodata[];
--
-
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