[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>

2 files changed, 7 insertions, 0 deletions

diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index feca5d961e2b..af4bfd012475 100644
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -20,6 +20,7 @@
 #include <linux/config.h>
 #include <linux/threads.h>
 #include <asm/percpu.h>
+#include <linux/cpumask.h>
 
 /* flag for disabling the tsc */
 extern int tsc_disable;
@@ -67,6 +68,9 @@ struct cpuinfo_x86 {
         char    pad0;
         int     x86_power;
         unsigned long loops_per_jiffy;
+#ifdef CONFIG_SMP
+        cpumask_t llc_shared_map;       /* cpus sharing the last level cache */
+#endif
         unsigned char x86_max_cores;    /* cpuid returned max cores value */
         unsigned char booted_cores;     /* number of cores as seen by OS */
         unsigned char apicid;
@@ -103,6 +107,7 @@ extern struct cpuinfo_x86 cpu_data[];
 
 extern  int phys_proc_id[NR_CPUS];
 extern  int cpu_core_id[NR_CPUS];
+extern  int cpu_llc_id[NR_CPUS];
 extern char ignore_fpu_irq;
 
 extern void identify_cpu(struct cpuinfo_x86 *);
diff --git a/include/asm-i386/topology.h b/include/asm-i386/topology.h
index aa958c6ee83e..b94e5eeef917 100644
--- a/include/asm-i386/topology.h
+++ b/include/asm-i386/topology.h
@@ -112,4 +112,6 @@ extern unsigned long node_remap_size[];
 
 #endif /* CONFIG_NUMA */
 
+extern cpumask_t cpu_coregroup_map(int cpu);
+
 #endif /* _ASM_I386_TOPOLOGY_H */