[IA64] VIRT_CPU_ACCOUNTING (accurate cpu time accounting)

This patch implements VIRT_CPU_ACCOUNTING for ia64,
which enable us to use more accurate cpu time accounting.

The VIRT_CPU_ACCOUNTING is an item of kernel config, which s390
and powerpc arch have.  By turning this config on, these archs
change the mechanism of cpu time accounting from tick-sampling
based one to state-transition based one.

The state-transition based accounting is done by checking time
(cycle counter in processor) at every state-transition point,
such as entrance/exit of kernel, interrupt, softirq etc.
The difference between point to point is the actual time consumed
during in the state. There is no doubt about that this value is
more accurate than that of tick-sampling based accounting.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/include/asm-ia64/thread_info.h b/include/asm-ia64/thread_info.h
index 93d83cbe0c8c..6da8069a0f77 100644
--- a/include/asm-ia64/thread_info.h
+++ b/include/asm-ia64/thread_info.h
@@ -31,6 +31,12 @@ struct thread_info {
         mm_segment_t addr_limit;        /* user-level address space limit */
         int preempt_count;              /* 0=premptable, <0=BUG; will also serve as bh-counter */
         struct restart_block restart_block;
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING
+        __u64 ac_stamp;
+        __u64 ac_leave;
+        __u64 ac_stime;
+        __u64 ac_utime;
+#endif
 };
 
 #define THREAD_SIZE                     KERNEL_STACK_SIZE
@@ -62,9 +68,17 @@ struct thread_info {
 #define task_stack_page(tsk)    ((void *)(tsk))
 
 #define __HAVE_THREAD_FUNCTIONS
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING
+#define setup_thread_stack(p, org)                      \
+        *task_thread_info(p) = *task_thread_info(org);  \
+        task_thread_info(p)->ac_stime = 0;              \
+        task_thread_info(p)->ac_utime = 0;              \
+        task_thread_info(p)->task = (p);
+#else
 #define setup_thread_stack(p, org) \
         *task_thread_info(p) = *task_thread_info(org); \
         task_thread_info(p)->task = (p);
+#endif
 #define end_of_stack(p) (unsigned long *)((void *)(p) + IA64_RBS_OFFSET)
 
 #define __HAVE_ARCH_TASK_STRUCT_ALLOCATOR