[PATCH] sched: new sched domain for representing multi-core

Add a new sched domain for representing multi-core with shared caches
between cores.  Consider a dual package system, each package containing two
cores and with last level cache shared between cores with in a package.  If
there are two runnable processes, with this appended patch those two
processes will be scheduled on different packages.

On such systems, with this patch we have observed 8% perf improvement with
specJBB(2 warehouse) benchmark and 35% improvement with CFP2000 rate(with 2
users).

This new domain will come into play only on multi-core systems with shared
caches.  On other systems, this sched domain will be removed by domain
degeneration code.  This new domain can be also used for implementing power
savings policy (see OLS 2005 CMP kernel scheduler paper for more details..
I will post another patch for power savings policy soon)

Most of the arch/* file changes are for cpu_coregroup_map() implementation.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index 7e3d6b6a4e96..a06a49075f10 100644
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -266,7 +266,7 @@ static void __init early_cpu_detect(void)
 void __cpuinit generic_identify(struct cpuinfo_x86 * c)
 {
 	u32 tfms, xlvl;
-	int junk;
+	int ebx;
 
 	if (have_cpuid_p()) {
 		/* Get vendor name */
@@ -282,7 +282,7 @@ void __cpuinit generic_identify(struct cpuinfo_x86 * c)
 		/* Intel-defined flags: level 0x00000001 */
 		if ( c->cpuid_level >= 0x00000001 ) {
 			u32 capability, excap;
-			cpuid(0x00000001, &tfms, &junk, &excap, &capability);
+			cpuid(0x00000001, &tfms, &ebx, &excap, &capability);
 			c->x86_capability[0] = capability;
 			c->x86_capability[4] = excap;
 			c->x86 = (tfms >> 8) & 15;
@@ -292,6 +292,11 @@ void __cpuinit generic_identify(struct cpuinfo_x86 * c)
 			if (c->x86 >= 0x6)
 				c->x86_model += ((tfms >> 16) & 0xF) << 4;
 			c->x86_mask = tfms & 15;
+#ifdef CONFIG_SMP
+			c->apicid = phys_pkg_id((ebx >> 24) & 0xFF, 0);
+#else
+			c->apicid = (ebx >> 24) & 0xFF;
+#endif
 		} else {
 			/* Have CPUID level 0 only - unheard of */
 			c->x86 = 4;
@@ -474,7 +479,6 @@ void __cpuinit detect_ht(struct cpuinfo_x86 *c)
 
 	cpuid(1, &eax, &ebx, &ecx, &edx);
 
-	c->apicid = phys_pkg_id((ebx >> 24) & 0xFF, 0);
 
 	if (!cpu_has(c, X86_FEATURE_HT) || cpu_has(c, X86_FEATURE_CMP_LEGACY))
 		return;