[PATCH] Create cpu_sibling_map for PPC64

[PATCH] Create cpu_sibling_map for PPC64

[Matthew Dobson]

In light of some proposed changes in the sched_domains code, I coded up
this little ditty that simply creates and populates a cpu_sibling_map
for PPC64 machines.  The patch just checks the CPU flags to determine if
the CPU supports SMT (aka Hyper-Threading aka Multi-Threading aka ...)
and fills in a mask of the siblings for each CPU in the system.  This
should allow us to build sched_domains for PPC64 with generic code in
kernel/sched.c for the SMT systems.  SMT is becoming more popular and is
turning up in more and more architectures.  I don't think it will be too
long until this feature is supported by most arches...

[mcd@arrakis source]$ diffstat
~/linux/patches/ppc64-cpu_sibling_map.patch
 arch/ppc64/kernel/smp.c |    7 +++++++
 include/asm-ppc64/smp.h |    1 +
 2 files changed, 8 insertions(+)

Signed-off-by: Matthew Dobson <colpatch@us.ibm.com>

-Matt


diff -Nurp --exclude-from=/home/mcd/.dontdiff linux-2.6.8-rc2-mm1/arch/ppc64/kernel/smp.c linux-2.6.8-rc2-mm1+ppc64-cpu_sibling_map/arch/ppc64/kernel/smp.c
--- linux-2.6.8-rc2-mm1/arch/ppc64/kernel/smp.c	2004-07-28 10:50:29.000000000 -0700
+++ linux-2.6.8-rc2-mm1+ppc64-cpu_sibling_map/arch/ppc64/kernel/smp.c	2004-07-28 12:02:38.000000000 -0700
@@ -64,6 +64,7 @@ cpumask_t cpu_possible_map = CPU_MASK_NO
 cpumask_t cpu_online_map = CPU_MASK_NONE;
 cpumask_t cpu_available_map = CPU_MASK_NONE;
 cpumask_t cpu_present_at_boot = CPU_MASK_NONE;
+cpumask_t cpu_sibling_map[NR_CPUS] = { [0 .. NR_CPUS-1] = CPU_MASK_NONE };
 
 EXPORT_SYMBOL(cpu_online_map);
 EXPORT_SYMBOL(cpu_possible_map);
@@ -870,6 +871,12 @@ void __init smp_prepare_cpus(unsigned in
 	for_each_cpu(cpu)
 		if (cpu != boot_cpuid)
 			smp_create_idle(cpu);
+
+	for_each_cpu(cpu) {
+		cpu_set(cpu, cpu_sibling_map[cpu]);
+		if (cur_cpu_spec->cpu_features & CPU_FTR_SMT)
+			cpu_set(cpu ^ 0x1, cpu_sibling_map[cpu]);
+	}
 }
 
 void __devinit smp_prepare_boot_cpu(void)
diff -Nurp --exclude-from=/home/mcd/.dontdiff linux-2.6.8-rc2-mm1/include/asm-ppc64/smp.h linux-2.6.8-rc2-mm1+ppc64-cpu_sibling_map/include/asm-ppc64/smp.h
--- linux-2.6.8-rc2-mm1/include/asm-ppc64/smp.h	2004-07-28 10:50:50.000000000 -0700
+++ linux-2.6.8-rc2-mm1+ppc64-cpu_sibling_map/include/asm-ppc64/smp.h	2004-07-28 12:02:38.000000000 -0700
@@ -49,6 +49,7 @@ extern cpumask_t cpu_present_at_boot;
 extern cpumask_t cpu_online_map;
 extern cpumask_t cpu_possible_map;
 extern cpumask_t cpu_available_map;
+extern cpumask_t cpu_sibling_map[NR_CPUS];
 
 #define cpu_present_at_boot(cpu) cpu_isset(cpu, cpu_present_at_boot)
 #define cpu_available(cpu)       cpu_isset(cpu, cpu_available_map) 

Re: [PATCH] Create cpu_sibling_map for PPC64

[Andrew Morton]

Matthew Dobson <colpatch@us.ibm.com> wrote:
>
> In light of some proposed changes in the sched_domains code, I coded up
>  this little ditty that simply creates and populates a cpu_sibling_map
>  for PPC64 machines.

err, did you compile it?

--- 25-power4/arch/ppc64/kernel/smp.c~create-cpu_sibling_map-for-ppc64-fix	2004-07-31 21:43:18.620845384 -0700
+++ 25-power4-akpm/arch/ppc64/kernel/smp.c	2004-07-31 21:43:21.258444408 -0700
@@ -64,7 +64,7 @@ cpumask_t cpu_possible_map = CPU_MASK_NO
 cpumask_t cpu_online_map = CPU_MASK_NONE;
 cpumask_t cpu_available_map = CPU_MASK_NONE;
 cpumask_t cpu_present_at_boot = CPU_MASK_NONE;
-cpumask_t cpu_sibling_map[NR_CPUS] = { [0 .. NR_CPUS-1] = CPU_MASK_NONE };
+cpumask_t cpu_sibling_map[NR_CPUS] = { [0 ... NR_CPUS-1] = CPU_MASK_NONE };
 
 EXPORT_SYMBOL(cpu_online_map);
 EXPORT_SYMBOL(cpu_possible_map);
_

Re: [PATCH] Create cpu_sibling_map for PPC64

[Matthew Dobson]

On Sat, 2004-07-31 at 21:45, Andrew Morton wrote:
> Matthew Dobson <colpatch@us.ibm.com> wrote:
> >
> > In light of some proposed changes in the sched_domains code, I coded up
> >  this little ditty that simply creates and populates a cpu_sibling_map
> >  for PPC64 machines.
> 
> err, did you compile it?

Oh, you wanted the version that compiles!?!  ;)  Besides me being really
bad at counting dots, our lab was down for a bit and I didn't test or
compile that before I sent it.  I was sending it more as an RFC than a
patch destined for acceptance (yet).  I still don't have access to a
machine to test it on, but I hope to snag some time soon.  Glad to see
*someone* is reading my code, though, since it obviously isn't me! ;)

-Matt

Re: [PATCH] Create cpu_sibling_map for PPC64

[Matthew Dobson]

On Sat, 2004-07-31 at 21:45, Andrew Morton wrote:
> Matthew Dobson <colpatch@us.ibm.com> wrote:
> >
> > In light of some proposed changes in the sched_domains code, I coded up
> >  this little ditty that simply creates and populates a cpu_sibling_map
> >  for PPC64 machines.
> 
> err, did you compile it?

Ok...  beyond not compiling it, I must have had my brain turned off when
I pushed the patch forward from 2.6.7-mm? to 2.6.8-rc2-mm1, because
cpu_sibling_map[] is already there, although only conditionally defined
for CONFIG_SCHED_SMT.  Talking to PPC developers at OLS, I think
cpu_sibling_map[] has (or more properly, will have) uses outside
sched_domains and thus deserves an unconditional definition.  Here's a
patch to change that.

[mcd@arrakis source]$ diffstat
~/linux/patches/ppc64-cpu_sibling_map.patch
 arch/ppc64/kernel/smp.c |    7 +------
 include/asm-ppc64/smp.h |    4 +---
 2 files changed, 2 insertions(+), 9 deletions(-)

-Matt


diff -Nurp --exclude-from=/home/mcd/.dontdiff linux-2.6.8-rc2-mm1/arch/ppc64/kernel/smp.c linux-2.6.8-rc2-mm1+ppc64-cpu_sibling_map/arch/ppc64/kernel/smp.c
--- linux-2.6.8-rc2-mm1/arch/ppc64/kernel/smp.c	2004-07-28 10:50:29.000000000 -0700
+++ linux-2.6.8-rc2-mm1+ppc64-cpu_sibling_map/arch/ppc64/kernel/smp.c	2004-08-02 14:27:18.000000000 -0700
@@ -55,15 +55,13 @@
 #include <asm/rtas.h>
 
 int smp_threads_ready;
-#ifdef CONFIG_SCHED_SMT
-cpumask_t cpu_sibling_map[NR_CPUS];
-#endif
 unsigned long cache_decay_ticks;
 
 cpumask_t cpu_possible_map = CPU_MASK_NONE;
 cpumask_t cpu_online_map = CPU_MASK_NONE;
 cpumask_t cpu_available_map = CPU_MASK_NONE;
 cpumask_t cpu_present_at_boot = CPU_MASK_NONE;
+cpumask_t cpu_sibling_map[NR_CPUS] = { [0 ... NR_CPUS-1] = CPU_MASK_NONE };
 
 EXPORT_SYMBOL(cpu_online_map);
 EXPORT_SYMBOL(cpu_possible_map);
@@ -448,14 +446,11 @@ static inline void look_for_more_cpus(vo
 	for (i = 0; i < maxcpus; i++)
 		cpu_set(i, cpu_possible_map);
 
-#ifdef CONFIG_SCHED_SMT
-	memset(cpu_sibling_map, 0, sizeof(cpu_sibling_map));
 	for_each_cpu(i) {
 		cpu_set(i, cpu_sibling_map[i]);
 		if (cur_cpu_spec->cpu_features & CPU_FTR_SMT)
 			cpu_set(i^1, cpu_sibling_map[i]);
 	}
-#endif
 }
 #else /* ... CONFIG_HOTPLUG_CPU */
 static inline int __devinit smp_startup_cpu(unsigned int lcpu)
diff -Nurp --exclude-from=/home/mcd/.dontdiff linux-2.6.8-rc2-mm1/include/asm-ppc64/smp.h linux-2.6.8-rc2-mm1+ppc64-cpu_sibling_map/include/asm-ppc64/smp.h
--- linux-2.6.8-rc2-mm1/include/asm-ppc64/smp.h	2004-07-28 10:50:50.000000000 -0700
+++ linux-2.6.8-rc2-mm1+ppc64-cpu_sibling_map/include/asm-ppc64/smp.h	2004-08-02 14:24:43.000000000 -0700
@@ -49,6 +49,7 @@ extern cpumask_t cpu_present_at_boot;
 extern cpumask_t cpu_online_map;
 extern cpumask_t cpu_possible_map;
 extern cpumask_t cpu_available_map;
+extern cpumask_t cpu_sibling_map[NR_CPUS];
 
 #define cpu_present_at_boot(cpu) cpu_isset(cpu, cpu_present_at_boot)
 #define cpu_available(cpu)       cpu_isset(cpu, cpu_available_map) 
@@ -73,9 +74,6 @@ void smp_init_pSeries(void);
 extern int __cpu_disable(void);
 extern void __cpu_die(unsigned int cpu);
 extern void cpu_die(void) __attribute__((noreturn));
-#ifdef CONFIG_SCHED_SMT
-extern cpumask_t cpu_sibling_map[NR_CPUS];
-#endif
 #endif /* !(CONFIG_SMP) */
 
 #define get_hard_smp_processor_id(CPU) (paca[(CPU)].hw_cpu_id)