[PATCH] i386: Selectable Frequency of the Timer Interrupt

Make the timer frequency selectable. The timer interrupt may cause bus
and memory contention in large NUMA systems since the interrupt occurs
on each processor HZ times per second.

Signed-off-by: Christoph Lameter <christoph@lameter.com>
Signed-off-by: Shai Fultheim <shai@scalex86.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index bfdcedef06e180ee5c63267e346c0a6cc914789c..d4ae5f9ceae6bb0a9375c53259d77fdaa70e16a4 100644 (file)
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -961,6 +961,8 @@ config SECCOMP
 
          If unsure, say Y. Only embedded should say N here.
 
+source kernel/Kconfig.hz
+
 endmenu
 
 

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 61ed16652347f7b3054fbb7b89b406346f940d4b..db259757dc8a4f97af912c8d56f5e0ae8d4ab81a 100644 (file)
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -402,6 +402,8 @@ config SECCOMP
 
          If unsure, say Y. Only embedded should say N here.
 
+source kernel/Kconfig.hz
+
 endmenu
 
 #

diff --git a/include/asm-i386/param.h b/include/asm-i386/param.h
index b6440526e42aa9b38d84cbd682cf8a0ac20b63c1..fa02e67ea86b7ba58f06e53032ac2aff7279c987 100644 (file)
--- a/include/asm-i386/param.h
+++ b/include/asm-i386/param.h
@@ -1,8 +1,10 @@
+#include <linux/config.h>
+
 #ifndef _ASMi386_PARAM_H
 #define _ASMi386_PARAM_H
 
 #ifdef __KERNEL__
-# define HZ            1000            /* Internal kernel timer frequency */
+# define HZ            CONFIG_HZ       /* Internal kernel timer frequency */
 # define USER_HZ       100             /* .. some user interfaces are in "ticks" */
 # define CLOCKS_PER_SEC                (USER_HZ)       /* like times() */
 #endif

diff --git a/include/asm-x86_64/param.h b/include/asm-x86_64/param.h
index b707f0568c9ede6420abf70388d6dd7fa716a3fc..40b11937180d37afc8bd32034bba45dafd6891ec 100644 (file)
--- a/include/asm-x86_64/param.h
+++ b/include/asm-x86_64/param.h
@@ -1,9 +1,11 @@
+#include <linux/config.h>
+
 #ifndef _ASMx86_64_PARAM_H
 #define _ASMx86_64_PARAM_H
 
 #ifdef __KERNEL__
-# define HZ            1000            /* Internal kernel timer frequency */
-# define USER_HZ       100          /* .. some user interfaces are in "ticks */
+# define HZ            CONFIG_HZ       /* Internal kernel timer frequency */
+# define USER_HZ       100             /* .. some user interfaces are in "ticks */
 #define CLOCKS_PER_SEC        (USER_HZ)       /* like times() */
 #endif
 

diff --git a/kernel/Kconfig.hz b/kernel/Kconfig.hz
new file mode 100644 (file)
index 0000000..248e1c3
--- /dev/null
+++ b/kernel/Kconfig.hz
@@ -0,0 +1,46 @@
+#
+# Timer Interrupt Frequency Configuration
+#
+
+choice
+       prompt "Timer frequency"
+       default HZ_250
+       help
+        Allows the configuration of the timer frequency. It is customary
+        to have the timer interrupt run at 1000 HZ but 100 HZ may be more
+        beneficial for servers and NUMA systems that do not need to have
+        a fast response for user interaction and that may experience bus
+        contention and cacheline bounces as a result of timer interrupts.
+        Note that the timer interrupt occurs on each processor in an SMP
+        environment leading to NR_CPUS * HZ number of timer interrupts
+        per second.
+
+
+       config HZ_100
+               bool "100 HZ"
+       help
+         100 HZ is a typical choice for servers, SMP and NUMA systems
+         with lots of processors that may show reduced performance if
+         too many timer interrupts are occurring.
+
+       config HZ_250
+               bool "250 HZ"
+       help
+        250 HZ is a good compromise choice allowing server performance
+        while also showing good interactive responsiveness even
+        on SMP and NUMA systems.
+
+       config HZ_1000
+               bool "1000 HZ"
+       help
+        1000 HZ is the preferred choice for desktop systems and other
+        systems requiring fast interactive responses to events.
+
+endchoice
+
+config HZ
+       int
+       default 100 if HZ_100
+       default 250 if HZ_250
+       default 1000 if HZ_1000
+