On large systems (like NUMA-Q, Intel Profusion, etc...), latency and
user responsiveness become much less important. The extra scheduling
overhead caused by higher HZ is bad.
This is x86-only right now. Is there any wider desire to tune this at
config time? Do any architecutures have strict rules as to what this
can be set to?
-- Dave Hansen haveblue@us.ibm.com
diff -ur linux-2.5.40/arch/i386/Config.help linux-2.5.40-hz_config/arch/i386/Config.help --- linux-2.5.40/arch/i386/Config.help 2002-10-01 00:06:17.000000000 -0700 +++ linux-2.5.40-hz_config/arch/i386/Config.help 2002-10-04 15:25:52.000000000 -0700 @@ -850,6 +850,17 @@ If in doubt, say N. +CONFIG_HZ + This is unrelated to your processor's speed. This variable alters + how often the system is asked to generate timer interrupts. A larger + value can lead to a more responsive system, but also causes extra + overhead from the increased number of context switches. + + In older kernels, this was set to 100. In 2.5, it was set to 1000. + HZ must be greater than 11 and less than 1536. + + If in doubt, leave it at the default of 1000. + CONFIG_CPU_FREQ_24_API This enables the /proc/sys/cpu/ sysctl interface for controlling CPUFreq, as known from the 2.4.-kernel patches for CPUFreq. Note diff -ur linux-2.5.40/arch/i386/config.in linux-2.5.40-hz_config/arch/i386/config.in --- linux-2.5.40/arch/i386/config.in 2002-10-04 14:25:29.000000000 -0700 +++ linux-2.5.40-hz_config/arch/i386/config.in 2002-10-04 15:21:21.000000000 -0700 @@ -208,6 +208,10 @@ fi fi +if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then + int 'Kernel Timer Frequency (HZ)' CONFIG_HZ 1000 +fi + tristate 'Toshiba Laptop support' CONFIG_TOSHIBA tristate 'Dell laptop support' CONFIG_I8K diff -ur linux-2.5.40/include/asm-i386/param.h linux-2.5.40-hz_config/include/asm-i386/param.h --- linux-2.5.40/include/asm-i386/param.h 2002-10-01 00:06:20.000000000 -0700 +++ linux-2.5.40-hz_config/include/asm-i386/param.h 2002-10-04 14:54:04.000000000 -0700 @@ -2,7 +2,7 @@ #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 -ur linux-2.5.40/include/linux/timex.h linux-2.5.40-hz_config/include/linux/timex.h --- linux-2.5.40/include/linux/timex.h 2002-10-01 00:06:15.000000000 -0700 +++ linux-2.5.40-hz_config/include/linux/timex.h 2002-10-04 15:24:04.000000000 -0700 @@ -76,7 +76,7 @@ #elif HZ >= 768 && HZ < 1536 # define SHIFT_HZ 10 #else -# error You lose. +# error Please use a HZ value which is between 12 and 1536 #endif /*
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This archive was generated by hypermail 2b29 : Mon Oct 07 2002 - 22:00:48 EST