x86: use percpu data for 4k hardirq and softirq stacks

Impact: economize memory for large NR_CPUS

percpu data is setup earlier than irq, we can use percpu data
to economize memory.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 15 insertions, 14 deletions

diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index e0f29be8ab0b..90cd94aba69a 100644
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -16,6 +16,7 @@
 #include <linux/cpu.h>
 #include <linux/delay.h>
 #include <linux/uaccess.h>
+#include <linux/percpu.h>
 
 #include <asm/apic.h>
 
@@ -55,13 +56,13 @@ static inline void print_stack_overflow(void) { }
 union irq_ctx {
         struct thread_info      tinfo;
         u32                     stack[THREAD_SIZE/sizeof(u32)];
-};
+} __attribute__((aligned(PAGE_SIZE)));
 
-static union irq_ctx *hardirq_ctx[NR_CPUS] __read_mostly;
-static union irq_ctx *softirq_ctx[NR_CPUS] __read_mostly;
+static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx);
+static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);
 
-static char softirq_stack[NR_CPUS * THREAD_SIZE] __page_aligned_bss;
-static char hardirq_stack[NR_CPUS * THREAD_SIZE] __page_aligned_bss;
+static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, hardirq_stack);
+static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, softirq_stack);
 
 static void call_on_stack(void *func, void *stack)
 {
@@ -81,7 +82,7 @@ execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
         u32 *isp, arg1, arg2;
 
         curctx = (union irq_ctx *) current_thread_info();
-        irqctx = hardirq_ctx[smp_processor_id()];
+        irqctx = __get_cpu_var(hardirq_ctx);
 
         /*
          * this is where we switch to the IRQ stack. However, if we are
@@ -125,34 +126,34 @@ void __cpuinit irq_ctx_init(int cpu)
 {
         union irq_ctx *irqctx;
 
-        if (hardirq_ctx[cpu])
+        if (per_cpu(hardirq_ctx, cpu))
                 return;
 
-        irqctx = (union irq_ctx*) &hardirq_stack[cpu*THREAD_SIZE];
+        irqctx = &per_cpu(hardirq_stack, cpu);
         irqctx->tinfo.task              = NULL;
         irqctx->tinfo.exec_domain       = NULL;
         irqctx->tinfo.cpu               = cpu;
         irqctx->tinfo.preempt_count     = HARDIRQ_OFFSET;
         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 
-        hardirq_ctx[cpu] = irqctx;
+        per_cpu(hardirq_ctx, cpu) = irqctx;
 
-        irqctx = (union irq_ctx *) &softirq_stack[cpu*THREAD_SIZE];
+        irqctx = &per_cpu(softirq_stack, cpu);
         irqctx->tinfo.task              = NULL;
         irqctx->tinfo.exec_domain       = NULL;
         irqctx->tinfo.cpu               = cpu;
         irqctx->tinfo.preempt_count     = 0;
         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 
-        softirq_ctx[cpu] = irqctx;
+        per_cpu(softirq_ctx, cpu) = irqctx;
 
         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
-               cpu, hardirq_ctx[cpu], softirq_ctx[cpu]);
+               cpu, per_cpu(hardirq_ctx, cpu),  per_cpu(softirq_ctx, cpu));
 }
 
 void irq_ctx_exit(int cpu)
 {
-        hardirq_ctx[cpu] = NULL;
+        per_cpu(hardirq_ctx, cpu) = NULL;
 }
 
 asmlinkage void do_softirq(void)
@@ -169,7 +170,7 @@ asmlinkage void do_softirq(void)
 
         if (local_softirq_pending()) {
                 curctx = current_thread_info();
-                irqctx = softirq_ctx[smp_processor_id()];
+                irqctx = __get_cpu_var(softirq_ctx);
                 irqctx->tinfo.task = curctx->task;
                 irqctx->tinfo.previous_esp = current_stack_pointer;