[patch] x86, apic: use logical flat on intel with <= 8 logical cpus

[patch] x86, apic: use logical flat on intel with <= 8 logical cpus

[Suresh Siddha]

On Intel platforms, we can use logical flat mode if there are <= 8
logical cpu's (irrespective of physical apic id values). This will
enable simplified and efficient IPI and device interrupt routing on
such platforms.

Fix the relevant comments while we are at it.

We can clean up default_setup_apic_routing() by using apic->probe()
but that is a different item.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index a34601f..0bde0a5 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -62,7 +62,7 @@ unsigned int boot_cpu_physical_apicid = -1U;
 /*
  * The highest APIC ID seen during enumeration.
  *
- * This determines the messaging protocol we can use: if all APIC IDs
+ * On AMD, this determines the messaging protocol we can use: if all APIC IDs
  * are in the 0 ... 7 range, then we can use logical addressing which
  * has some performance advantages (better broadcasting).
  *
@@ -1917,24 +1917,14 @@ void __cpuinit generic_processor_info(int apicid, int version)
 		max_physical_apicid = apicid;
 
 #ifdef CONFIG_X86_32
-	/*
-	 * Would be preferable to switch to bigsmp when CONFIG_HOTPLUG_CPU=y
-	 * but we need to work other dependencies like SMP_SUSPEND etc
-	 * before this can be done without some confusion.
-	 * if (CPU_HOTPLUG_ENABLED || num_processors > 8)
-	 *       - Ashok Raj <ashok.raj@intel.com>
-	 */
-	if (max_physical_apicid >= 8) {
-		switch (boot_cpu_data.x86_vendor) {
+	switch (boot_cpu_data.x86_vendor) {
 		case X86_VENDOR_INTEL:
-			if (!APIC_XAPIC(version)) {
-				def_to_bigsmp = 0;
-				break;
-			}
-			/* If P4 and above fall through */
+			if (num_processors > 8)
+				def_to_bigsmp = 1;
+			break;
 		case X86_VENDOR_AMD:
-			def_to_bigsmp = 1;
-		}
+			if (max_physical_apicid >= 8)
+				def_to_bigsmp = 1;
 	}
 #endif
 
diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
index 65edc18..2e562a3 100644
--- a/arch/x86/kernel/apic/probe_64.c
+++ b/arch/x86/kernel/apic/probe_64.c
@@ -64,16 +64,23 @@ void __init default_setup_apic_routing(void)
 			apic = &apic_x2apic_phys;
 		else
 			apic = &apic_x2apic_cluster;
-		printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
 	}
 #endif
 
 	if (apic == &apic_flat) {
-		if (max_physical_apicid >= 8)
-			apic = &apic_physflat;
-		printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
+		switch (boot_cpu_data.x86_vendor) {
+			case X86_VENDOR_INTEL:
+				if (num_processors > 8)
+					apic = &apic_physflat;
+				break;
+			case X86_VENDOR_AMD:
+		 		if (max_physical_apicid >= 8)
+					apic = &apic_physflat;
+		}
 	}
 
+	printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
+
 	if (is_vsmp_box()) {
 		/* need to update phys_pkg_id */
 		apic->phys_pkg_id = apicid_phys_pkg_id;

Re: [patch] x86, apic: use logical flat on intel with <= 8 logical cpus

[Daniel Walker]

On Fri, 2009-09-18 at 19:05 -0700, Suresh Siddha wrote:
> +               switch (boot_cpu_data.x86_vendor) {
> +                       case X86_VENDOR_INTEL:
> +                               if (num_processors > 8)
> +                                       apic = &apic_physflat;
> +                               break;
> +                       case X86_VENDOR_AMD:
> +                               if (max_physical_apicid >= 8)
> +                                       apic = &apic_physflat;
> +               }

There are a couple of checkpatch issues in this patch .. Could you run
it through and fix the errors that show up.. One is that you need 1 less
tab for the code inside the switch statement .. You have another switch
statement in apic.c that needs similar attention .

Daniel

Re: [patch] x86, apic: use logical flat on intel with <= 8 logical cpus

[Suresh Siddha]

On Fri, 2009-09-18 at 19:19 -0700, Daniel Walker wrote:
> There are a couple of checkpatch issues in this patch .. Could you run
> it through and fix the errors that show up.. One is that you need 1 less
> tab for the code inside the switch statement .. You have another switch
> statement in apic.c that needs similar attention .

Oops. Here it is. Thanks!

---

From: Suresh Siddha <suresh.b.siddha@intel.com>
Subject: x86, apic: use logical flat on intel with <= 8 logical cpus

On Intel platforms, we can use logical flat mode if there are <= 8
logical cpu's (irrespective of physical apic id values). This will
enable simplified and efficient IPI and device interrupt routing on
such platforms.

Fix the relevant comments while we are at it.

We can clean up default_setup_apic_routing() by using apic->probe()
but that is a different item.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index a34601f..e3654ec 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -62,7 +62,7 @@ unsigned int boot_cpu_physical_apicid = -1U;
 /*
  * The highest APIC ID seen during enumeration.
  *
- * This determines the messaging protocol we can use: if all APIC IDs
+ * On AMD, this determines the messaging protocol we can use: if all APIC IDs
  * are in the 0 ... 7 range, then we can use logical addressing which
  * has some performance advantages (better broadcasting).
  *
@@ -1917,24 +1917,14 @@ void __cpuinit generic_processor_info(int apicid, int version)
 		max_physical_apicid = apicid;
 
 #ifdef CONFIG_X86_32
-	/*
-	 * Would be preferable to switch to bigsmp when CONFIG_HOTPLUG_CPU=y
-	 * but we need to work other dependencies like SMP_SUSPEND etc
-	 * before this can be done without some confusion.
-	 * if (CPU_HOTPLUG_ENABLED || num_processors > 8)
-	 *       - Ashok Raj <ashok.raj@intel.com>
-	 */
-	if (max_physical_apicid >= 8) {
-		switch (boot_cpu_data.x86_vendor) {
-		case X86_VENDOR_INTEL:
-			if (!APIC_XAPIC(version)) {
-				def_to_bigsmp = 0;
-				break;
-			}
-			/* If P4 and above fall through */
-		case X86_VENDOR_AMD:
+	switch (boot_cpu_data.x86_vendor) {
+	case X86_VENDOR_INTEL:
+		if (num_processors > 8)
+			def_to_bigsmp = 1;
+		break;
+	case X86_VENDOR_AMD:
+		if (max_physical_apicid >= 8)
 			def_to_bigsmp = 1;
-		}
 	}
 #endif
 
diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
index 65edc18..41e8509 100644
--- a/arch/x86/kernel/apic/probe_64.c
+++ b/arch/x86/kernel/apic/probe_64.c
@@ -64,16 +64,23 @@ void __init default_setup_apic_routing(void)
 			apic = &apic_x2apic_phys;
 		else
 			apic = &apic_x2apic_cluster;
-		printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
 	}
 #endif
 
 	if (apic == &apic_flat) {
-		if (max_physical_apicid >= 8)
-			apic = &apic_physflat;
-		printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
+		switch (boot_cpu_data.x86_vendor) {
+		case X86_VENDOR_INTEL:
+			if (num_processors > 8)
+				apic = &apic_physflat;
+			break;
+		case X86_VENDOR_AMD:
+			if (max_physical_apicid >= 8)
+				apic = &apic_physflat;
+		}
 	}
 
+	printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
+
 	if (is_vsmp_box()) {
 		/* need to update phys_pkg_id */
 		apic->phys_pkg_id = apicid_phys_pkg_id;

Re: [patch] x86, apic: use logical flat on intel with <= 8 logical cpus

[Daniel Walker]

On Fri, 2009-09-18 at 19:29 -0700, Suresh Siddha wrote:
> On Fri, 2009-09-18 at 19:19 -0700, Daniel Walker wrote:
> > There are a couple of checkpatch issues in this patch .. Could you run
> > it through and fix the errors that show up.. One is that you need 1 less
> > tab for the code inside the switch statement .. You have another switch
> > statement in apic.c that needs similar attention .
> 
> Oops. Here it is. Thanks!
> 

Much better thanks..

Daniel

[tip:x86/urgent] x86, apic: Use logical flat on intel with <= 8 logical cpus

[tip-bot for Suresh Siddha]

Commit-ID:  2fbd07a5f5d1295fa9b0c0564ec27da7c276a75a
Gitweb:     http://git.kernel.org/tip/2fbd07a5f5d1295fa9b0c0564ec27da7c276a75a
Author:     Suresh Siddha <suresh.b.siddha@intel.com>
AuthorDate: Fri, 18 Sep 2009 19:29:59 -0700
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 19 Sep 2009 09:20:05 +0200

x86, apic: Use logical flat on intel with <= 8 logical cpus

On Intel platforms, we can use logical flat mode if there are <= 8
logical cpu's (irrespective of physical apic id values). This will
enable simplified and efficient IPI and device interrupt routing on
such platforms.

Fix the relevant comments while we are at it.

We can clean up default_setup_apic_routing() by using apic->probe()
but that is a different item.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: "yinghai@kernel.org" <yinghai@kernel.org>
LKML-Reference: <1253327399.3948.747.camel@sbs-t61.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 arch/x86/kernel/apic/apic.c     |   26 ++++++++------------------
 arch/x86/kernel/apic/probe_64.c |   15 +++++++++++----
 2 files changed, 19 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 79e5b92..072aea6 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -61,7 +61,7 @@ unsigned int boot_cpu_physical_apicid = -1U;
 /*
  * The highest APIC ID seen during enumeration.
  *
- * This determines the messaging protocol we can use: if all APIC IDs
+ * On AMD, this determines the messaging protocol we can use: if all APIC IDs
  * are in the 0 ... 7 range, then we can use logical addressing which
  * has some performance advantages (better broadcasting).
  *
@@ -1915,24 +1915,14 @@ void __cpuinit generic_processor_info(int apicid, int version)
 		max_physical_apicid = apicid;
 
 #ifdef CONFIG_X86_32
-	/*
-	 * Would be preferable to switch to bigsmp when CONFIG_HOTPLUG_CPU=y
-	 * but we need to work other dependencies like SMP_SUSPEND etc
-	 * before this can be done without some confusion.
-	 * if (CPU_HOTPLUG_ENABLED || num_processors > 8)
-	 *       - Ashok Raj <ashok.raj@intel.com>
-	 */
-	if (max_physical_apicid >= 8) {
-		switch (boot_cpu_data.x86_vendor) {
-		case X86_VENDOR_INTEL:
-			if (!APIC_XAPIC(version)) {
-				def_to_bigsmp = 0;
-				break;
-			}
-			/* If P4 and above fall through */
-		case X86_VENDOR_AMD:
+	switch (boot_cpu_data.x86_vendor) {
+	case X86_VENDOR_INTEL:
+		if (num_processors > 8)
+			def_to_bigsmp = 1;
+		break;
+	case X86_VENDOR_AMD:
+		if (max_physical_apicid >= 8)
 			def_to_bigsmp = 1;
-		}
 	}
 #endif
 
diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
index 65edc18..c4cbd30 100644
--- a/arch/x86/kernel/apic/probe_64.c
+++ b/arch/x86/kernel/apic/probe_64.c
@@ -64,16 +64,23 @@ void __init default_setup_apic_routing(void)
 			apic = &apic_x2apic_phys;
 		else
 			apic = &apic_x2apic_cluster;
-		printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
 	}
 #endif
 
 	if (apic == &apic_flat) {
-		if (max_physical_apicid >= 8)
-			apic = &apic_physflat;
-		printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
+		switch (boot_cpu_data.x86_vendor) {
+		case X86_VENDOR_INTEL:
+			if (num_processors > 8)
+				apic = &apic_physflat;
+			break;
+		case X86_VENDOR_AMD:
+			if (max_physical_apicid >= 8)
+				apic = &apic_physflat;
+		}
 	}
 
+	printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
+
 	if (is_vsmp_box()) {
 		/* need to update phys_pkg_id */
 		apic->phys_pkg_id = apicid_phys_pkg_id;