[PATCH] Export cpu topology in sysfs

The patch implements cpu topology exportation by sysfs.

Items (attributes) are similar to /proc/cpuinfo.

1) /sys/devices/system/cpu/cpuX/topology/physical_package_id:
	represent the physical package id of  cpu X;
2) /sys/devices/system/cpu/cpuX/topology/core_id:
	represent the cpu core id to cpu X;
3) /sys/devices/system/cpu/cpuX/topology/thread_siblings:
	represent the thread siblings to cpu X in the same core;
4) /sys/devices/system/cpu/cpuX/topology/core_siblings:
	represent the thread siblings to cpu X in the same physical package;

To implement it in an architecture-neutral way, a new source file,
driver/base/topology.c, is to export the 5 attributes.

If one architecture wants to support this feature, it just needs to
implement 4 defines, typically in file include/asm-XXX/topology.h.
The 4 defines are:
#define topology_physical_package_id(cpu)
#define topology_core_id(cpu)
#define topology_thread_siblings(cpu)
#define topology_core_siblings(cpu)

The type of **_id is int.
The type of siblings is cpumask_t.

To be consistent on all architectures, the 4 attributes should have
deafult values if their values are unavailable. Below is the rule.

1) physical_package_id: If cpu has no physical package id, -1 is the
default value.

2) core_id: If cpu doesn't support multi-core, its core id is 0.

3) thread_siblings: Just include itself, if the cpu doesn't support
HT/multi-thread.

4) core_siblings: Just include itself, if the cpu doesn't support
multi-core and HT/Multi-thread.

So be careful when declaring the 4 defines in include/asm-XXX/topology.h.

If an attribute isn't defined on an architecture, it won't be exported.

Thank Nathan, Greg, Andi, Paul and Venki.

The patch provides defines for i386/x86_64/ia64.

Signed-off-by: Zhang, Yanmin <yanmin.zhang@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/asm-ia64/topology.h b/include/asm-ia64/topology.h
index 412ef8e493a8..3ee19dfa46df 100644
--- a/include/asm-ia64/topology.h
+++ b/include/asm-ia64/topology.h
@@ -102,6 +102,13 @@ void build_cpu_to_node_map(void);
 
 #endif /* CONFIG_NUMA */
 
+#ifdef CONFIG_SMP
+#define topology_physical_package_id(cpu)       (cpu_data(cpu)->socket_id)
+#define topology_core_id(cpu)                   (cpu_data(cpu)->core_id)
+#define topology_core_siblings(cpu)             (cpu_core_map[cpu])
+#define topology_thread_siblings(cpu)           (cpu_sibling_map[cpu])
+#endif
+
 #include <asm-generic/topology.h>
 
 #endif /* _ASM_IA64_TOPOLOGY_H */