[patch] consolidate PREEMPT options into kernel/Kconfig.preempt

[patch] consolidate PREEMPT options into kernel/Kconfig.preempt

[Ingo Molnar]

any objections? This is against the tail of the scheduler-patchset in 
-mm. For now i only included architectures that support the full range 
of preemption features - other architectures can still cherry-pick them 
if they want to. (I did not do a Kconfig.sched, because other scheduler 
features are much more hardware-dependent.)

--

this patch consolidates the CONFIG_PREEMPT and CONFIG_PREEMPT_BKL 
preemption options into kernel/Kconfig.preempt. This, besides reducing 
source-code, also enables more centralized tweaking of preemption 
related options.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

 arch/i386/Kconfig      |   23 +----------------------
 arch/ppc64/Kconfig     |   21 +--------------------
 arch/x86_64/Kconfig    |   29 ++---------------------------
 kernel/Kconfig.preempt |   24 ++++++++++++++++++++++++
 4 files changed, 28 insertions(+), 69 deletions(-)

--- linux/kernel/Kconfig.preempt.orig
+++ linux/kernel/Kconfig.preempt
@@ -0,0 +1,24 @@
+
+config PREEMPT
+	bool "Preemptible Kernel"
+	help
+	  This option reduces the latency of the kernel when reacting to
+	  real-time or interactive events by allowing a low priority process to
+	  be preempted even if it is in kernel mode executing a system call.
+	  This allows applications to run more reliably even when the system is
+	  under load.
+
+	  Say Y here if you are building a kernel for a desktop, embedded
+	  or real-time system.  Say N if you are unsure.
+
+config PREEMPT_BKL
+	bool "Preempt The Big Kernel Lock"
+	depends on PREEMPT
+	default y
+	help
+	  This option reduces the latency of the kernel by making the
+	  big kernel lock preemptible.
+
+	  Say Y here if you are building a kernel for a desktop system.
+	  Say N if you are unsure.
+
--- linux/arch/x86_64/Kconfig.orig
+++ linux/arch/x86_64/Kconfig
@@ -207,33 +207,6 @@ config SMP
 
 	  If you don't know what to do here, say N.
 
-config PREEMPT
-	bool "Preemptible Kernel"
-	---help---
-	  This option reduces the latency of the kernel when reacting to
-	  real-time or interactive events by allowing a low priority process to
-	  be preempted even if it is in kernel mode executing a system call.
-	  This allows applications to run more reliably even when the system is
-	  under load. On contrary it may also break your drivers and add
-	  priority inheritance problems to your system. Don't select it if
-	  you rely on a stable system or have slightly obscure hardware.
-	  It's also not very well tested on x86-64 currently.
-	  You have been warned.
-
-	  Say Y here if you are feeling brave and building a kernel for a
-	  desktop, embedded or real-time system.  Say N if you are unsure.
-
-config PREEMPT_BKL
-	bool "Preempt The Big Kernel Lock"
-	depends on PREEMPT
-	default y
-	help
-	  This option reduces the latency of the kernel by making the
-	  big kernel lock preemptible.
-
-	  Say Y here if you are building a kernel for a desktop system.
-	  Say N if you are unsure.
-
 config SCHED_SMT
 	bool "SMT (Hyperthreading) scheduler support"
 	depends on SMP
@@ -244,6 +217,8 @@ config SCHED_SMT
 	  cost of slightly increased overhead in some places. If unsure say
 	  N here.
 
+ource "kernel/Kconfig.preempt"
+
 config K8_NUMA
        bool "K8 NUMA support"
        select NUMA
--- linux/arch/ppc64/Kconfig.orig
+++ linux/arch/ppc64/Kconfig
@@ -268,26 +268,7 @@ config SCHED_SMT
 	  when dealing with POWER5 cpus at a cost of slightly increased
 	  overhead in some places. If unsure say N here.
 
-config PREEMPT
-	bool "Preemptible Kernel"
-	help
-	  This option reduces the latency of the kernel when reacting to
-	  real-time or interactive events by allowing a low priority process to
-	  be preempted even if it is in kernel mode executing a system call.
-
-	  Say Y here if you are building a kernel for a desktop, embedded
-	  or real-time system.  Say N if you are unsure.
-
-config PREEMPT_BKL
-	bool "Preempt The Big Kernel Lock"
-	depends on PREEMPT
-	default y
-	help
-	  This option reduces the latency of the kernel by making the
-	  big kernel lock preemptible.
-
-	  Say Y here if you are building a kernel for a desktop system.
-	  Say N if you are unsure.
+source "kernel/Kconfig.preempt"
 
 config EEH
 	bool "PCI Extended Error Handling (EEH)" if EMBEDDED
--- linux/arch/i386/Kconfig.orig
+++ linux/arch/i386/Kconfig
@@ -510,28 +510,7 @@ config SCHED_SMT
 	  cost of slightly increased overhead in some places. If unsure say
 	  N here.
 
-config PREEMPT
-	bool "Preemptible Kernel"
-	help
-	  This option reduces the latency of the kernel when reacting to
-	  real-time or interactive events by allowing a low priority process to
-	  be preempted even if it is in kernel mode executing a system call.
-	  This allows applications to run more reliably even when the system is
-	  under load.
-
-	  Say Y here if you are building a kernel for a desktop, embedded
-	  or real-time system.  Say N if you are unsure.
-
-config PREEMPT_BKL
-	bool "Preempt The Big Kernel Lock"
-	depends on PREEMPT
-	default y
-	help
-	  This option reduces the latency of the kernel by making the
-	  big kernel lock preemptible.
-
-	  Say Y here if you are building a kernel for a desktop system.
-	  Say N if you are unsure.
+source "kernel/Kconfig.preempt"
 
 config X86_UP_APIC
 	bool "Local APIC support on uniprocessors"

Re: [patch] consolidate PREEMPT options into kernel/Kconfig.preempt

[Ingo Molnar]

[-- Attachment #1: Type: text/plain, Size: 389 bytes --]


typo in the x86_64 change, fix below. (i've also attached a respun full 
patch)

	Ingo

--- linux/arch/x86_64/Kconfig.orig
+++ linux/arch/x86_64/Kconfig
@@ -217,7 +217,7 @@ config SCHED_SMT
 	  cost of slightly increased overhead in some places. If unsure say
 	  N here.
 
-ource "kernel/Kconfig.preempt"
+source "kernel/Kconfig.preempt"
 
 config K8_NUMA
        bool "K8 NUMA support"

[-- Attachment #2: consolidate-preempt-options.patch --]
[-- Type: text/plain, Size: 4970 bytes --]


this patch consolidates the CONFIG_PREEMPT and CONFIG_PREEMPT_BKL 
preemption options into kernel/Kconfig.preempt. This, besides reducing 
source-code, also enables more centralized tweaking of preemption 
related options.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

 arch/i386/Kconfig      |   23 +----------------------
 arch/ppc64/Kconfig     |   21 +--------------------
 arch/x86_64/Kconfig    |   29 ++---------------------------
 kernel/Kconfig.preempt |   24 ++++++++++++++++++++++++
 4 files changed, 28 insertions(+), 69 deletions(-)

--- linux/kernel/Kconfig.preempt.orig
+++ linux/kernel/Kconfig.preempt
@@ -0,0 +1,24 @@
+
+config PREEMPT
+	bool "Preemptible Kernel"
+	help
+	  This option reduces the latency of the kernel when reacting to
+	  real-time or interactive events by allowing a low priority process to
+	  be preempted even if it is in kernel mode executing a system call.
+	  This allows applications to run more reliably even when the system is
+	  under load.
+
+	  Say Y here if you are building a kernel for a desktop, embedded
+	  or real-time system.  Say N if you are unsure.
+
+config PREEMPT_BKL
+	bool "Preempt The Big Kernel Lock"
+	depends on PREEMPT
+	default y
+	help
+	  This option reduces the latency of the kernel by making the
+	  big kernel lock preemptible.
+
+	  Say Y here if you are building a kernel for a desktop system.
+	  Say N if you are unsure.
+
--- linux/arch/x86_64/Kconfig.orig
+++ linux/arch/x86_64/Kconfig
@@ -207,33 +207,6 @@ config SMP
 
 	  If you don't know what to do here, say N.
 
-config PREEMPT
-	bool "Preemptible Kernel"
-	---help---
-	  This option reduces the latency of the kernel when reacting to
-	  real-time or interactive events by allowing a low priority process to
-	  be preempted even if it is in kernel mode executing a system call.
-	  This allows applications to run more reliably even when the system is
-	  under load. On contrary it may also break your drivers and add
-	  priority inheritance problems to your system. Don't select it if
-	  you rely on a stable system or have slightly obscure hardware.
-	  It's also not very well tested on x86-64 currently.
-	  You have been warned.
-
-	  Say Y here if you are feeling brave and building a kernel for a
-	  desktop, embedded or real-time system.  Say N if you are unsure.
-
-config PREEMPT_BKL
-	bool "Preempt The Big Kernel Lock"
-	depends on PREEMPT
-	default y
-	help
-	  This option reduces the latency of the kernel by making the
-	  big kernel lock preemptible.
-
-	  Say Y here if you are building a kernel for a desktop system.
-	  Say N if you are unsure.
-
 config SCHED_SMT
 	bool "SMT (Hyperthreading) scheduler support"
 	depends on SMP
@@ -244,6 +217,8 @@ config SCHED_SMT
 	  cost of slightly increased overhead in some places. If unsure say
 	  N here.
 
+source "kernel/Kconfig.preempt"
+
 config K8_NUMA
        bool "K8 NUMA support"
        select NUMA
--- linux/arch/ppc64/Kconfig.orig
+++ linux/arch/ppc64/Kconfig
@@ -268,26 +268,7 @@ config SCHED_SMT
 	  when dealing with POWER5 cpus at a cost of slightly increased
 	  overhead in some places. If unsure say N here.
 
-config PREEMPT
-	bool "Preemptible Kernel"
-	help
-	  This option reduces the latency of the kernel when reacting to
-	  real-time or interactive events by allowing a low priority process to
-	  be preempted even if it is in kernel mode executing a system call.
-
-	  Say Y here if you are building a kernel for a desktop, embedded
-	  or real-time system.  Say N if you are unsure.
-
-config PREEMPT_BKL
-	bool "Preempt The Big Kernel Lock"
-	depends on PREEMPT
-	default y
-	help
-	  This option reduces the latency of the kernel by making the
-	  big kernel lock preemptible.
-
-	  Say Y here if you are building a kernel for a desktop system.
-	  Say N if you are unsure.
+source "kernel/Kconfig.preempt"
 
 config EEH
 	bool "PCI Extended Error Handling (EEH)" if EMBEDDED
--- linux/arch/i386/Kconfig.orig
+++ linux/arch/i386/Kconfig
@@ -510,28 +510,7 @@ config SCHED_SMT
 	  cost of slightly increased overhead in some places. If unsure say
 	  N here.
 
-config PREEMPT
-	bool "Preemptible Kernel"
-	help
-	  This option reduces the latency of the kernel when reacting to
-	  real-time or interactive events by allowing a low priority process to
-	  be preempted even if it is in kernel mode executing a system call.
-	  This allows applications to run more reliably even when the system is
-	  under load.
-
-	  Say Y here if you are building a kernel for a desktop, embedded
-	  or real-time system.  Say N if you are unsure.
-
-config PREEMPT_BKL
-	bool "Preempt The Big Kernel Lock"
-	depends on PREEMPT
-	default y
-	help
-	  This option reduces the latency of the kernel by making the
-	  big kernel lock preemptible.
-
-	  Say Y here if you are building a kernel for a desktop system.
-	  Say N if you are unsure.
+source "kernel/Kconfig.preempt"
 
 config X86_UP_APIC
 	bool "Local APIC support on uniprocessors"