Linux系统的宏HZ的值一般在体系相关的目录下,例如arch/arm/include/asm/param.h下,代码如下:
- /* -------------------------------------------------------------------- */
- /*
- * arch/arm/include/asm/param.h
- *
- * Copyright (C) 1995-1999 Russell King
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
- #ifndef __ASM_PARAM_H
- #define __ASM_PARAM_H
- #ifdef __KERNEL__
- # define HZ CONFIG_HZ /* Internal kernel timer frequency */
- # define USER_HZ 100 /* User interfaces are in "ticks" */
- # define CLOCKS_PER_SEC (USER_HZ) /* like times() */
- #else
- # define HZ 100
- #endif
- #define EXEC_PAGESIZE 4096
- #ifndef NOGROUP
- #define NOGROUP (-1)
- #endif
- /* max length of hostname */
- #define MAXHOSTNAMELEN 64
- #endif
- /* -------------------------------------------------------------------- */
一般在make menuconfig下面会有100、250、300、1000的默认配置值,但是其实这些值包含在kernel/timeconst.pl中,这是一个perl脚本:
- /* -------------------------------------------------------------------- */
- #!/usr/bin/perl
- # -----------------------------------------------------------------------
- #
- # Copyright 2007-2008 rPath, Inc. - All Rights Reserved
- #
- # This file is part of the Linux kernel, and is made available under
- # the terms of the GNU General Public License version 2 or (at your
- # option) any later version; incorporated herein by reference.
- #
- # -----------------------------------------------------------------------
- #
- #
- # Usage: timeconst.pl HZ > timeconst.h
- #
- # Precomputed values for systems without Math::BigInt
- # Generated by:
- # timeconst.pl --can 24 32 48 64 100 122 128 200 250 256 300 512 1000 1024 1200
- %canned_values = (
- 24 => [
- '0xa6aaaaab','0x2aaaaaa',26,
- 125,3,
- '0xc49ba5e4','0x1fbe76c8b4',37,
- 3,125,
- '0xa2c2aaab','0xaaaa',16,
- 125000,3,
- '0xc9539b89','0x7fffbce4217d',47,
- 3,125000,
- ], 32 => [
- '0xfa000000','0x6000000',27,
- 125,4,
- '0x83126e98','0xfdf3b645a',36,
- 4,125,
- '0xf4240000','0x0',17,
- 31250,1,
- '0x8637bd06','0x3fff79c842fa',46,
- 1,31250,
- ], 48 => [
- '0xa6aaaaab','0x6aaaaaa',27,
- 125,6,
- '0xc49ba5e4','0xfdf3b645a',36,
- 6,125,
- '0xa2c2aaab','0x15555',17,
- 62500,3,
- '0xc9539b89','0x3fffbce4217d',46,
- 3,62500,
- ], 64 => [
- '0xfa000000','0xe000000',28,
- 125,8,
- '0x83126e98','0x7ef9db22d',35,
- 8,125,
- '0xf4240000','0x0',18,
- 15625,1,
- '0x8637bd06','0x1fff79c842fa',45,
- 1,15625,
- ], 100 => [
- '0xa0000000','0x0',28,
- 10,1,
- '0xcccccccd','0x733333333',35,
- 1,10,
- '0x9c400000','0x0',18,
- 10000,1,
- '0xd1b71759','0x1fff2e48e8a7',45,
- 1,10000,
- ], 122 => [
- '0x8325c53f','0xfbcda3a',28,
- 500,61,
- '0xf9db22d1','0x7fbe76c8b',35,
- 61,500,
- '0x8012e2a0','0x3ef36',18,
- 500000,61,
- '0xffda4053','0x1ffffbce4217',45,
- 61,500000,
- ], 128 => [
- '0xfa000000','0x1e000000',29,
- 125,16,
- '0x83126e98','0x3f7ced916',34,
- 16,125,
- '0xf4240000','0x40000',19,
- 15625,2,
- '0x8637bd06','0xfffbce4217d',44,
- 2,15625,
- ], 200 => [
- '0xa0000000','0x0',29,
- 5,1,
- '0xcccccccd','0x333333333',34,
- 1,5,
- '0x9c400000','0x0',19,
- 5000,1,
- '0xd1b71759','0xfff2e48e8a7',44,
- 1,5000,
- ], 250 => [
- '0x80000000','0x0',29,
- 4,1,
- '0x80000000','0x180000000',33,
- 1,4,
- '0xfa000000','0x0',20,
- 4000,1,
- '0x83126e98','0x7ff7ced9168',43,
- 1,4000,
- ], 256 => [
- '0xfa000000','0x3e000000',30,
- 125,32,
- '0x83126e98','0x1fbe76c8b',33,
- 32,125,
- '0xf4240000','0xc0000',20,
- 15625,4,
- '0x8637bd06','0x7ffde7210be',43,
- 4,15625,
- ], 300 => [
- '0xd5555556','0x2aaaaaaa',30,
- 10,3,
- '0x9999999a','0x1cccccccc',33,
- 3,10,
- '0xd0555556','0xaaaaa',20,
- 10000,3,
- '0x9d495183','0x7ffcb923a29',43,
- 3,10000,
- ], 512 => [
- '0xfa000000','0x7e000000',31,
- 125,64,
- '0x83126e98','0xfdf3b645',32,
- 64,125,
- '0xf4240000','0x1c0000',21,
- 15625,8,
- '0x8637bd06','0x3ffef39085f',42,
- 8,15625,
- ], 1000 => [
- '0x80000000','0x0',31,
- 1,1,
- '0x80000000','0x0',31,
- 1,1,
- '0xfa000000','0x0',22,
- 1000,1,
- '0x83126e98','0x1ff7ced9168',41,
- 1,1000,
- ], 1024 => [
- '0xfa000000','0xfe000000',32,
- 125,128,
- '0x83126e98','0x7ef9db22',31,
- 128,125,
- '0xf4240000','0x3c0000',22,
- 15625,16,
- '0x8637bd06','0x1fff79c842f',41,
- 16,15625,
- ], 1200 => [
- '0xd5555556','0xd5555555',32,
- 5,6,
- '0x9999999a','0x66666666',31,
- 6,5,
- '0xd0555556','0x2aaaaa',22,
- 2500,3,
- '0x9d495183','0x1ffcb923a29',41,
- 3,2500,
- ]
- );
- /* -------------------------------------------------------------------- */
上面红色部分简绍了使用方法,有的时候,修改了HZ的值,可能要手动运行一下,例如,修改HZ=512,则可以在kernel目录下: timeconst.pl 512 > timeconst.h
也就是说kernel目录下的timeconst.h是动态生成的
- /* -------------------------------------------------------------------- */
- /* Automatically generated by kernel/timeconst.pl */
- /* Conversion constants for HZ == 512 */
- #ifndef KERNEL_TIMECONST_H
- #define KERNEL_TIMECONST_H
- #include <linux/param.h>
- #include <linux/types.h>
- #if HZ != 512
- #error "kernel/timeconst.h has the wrong HZ value!"
- #endif
- #define HZ_TO_MSEC_MUL32 U64_C(0xfa000000)
- #define HZ_TO_MSEC_ADJ32 U64_C(0x7e000000)
- #define HZ_TO_MSEC_SHR32 31
- #define HZ_TO_MSEC_NUM U64_C(125)
- #define HZ_TO_MSEC_DEN U64_C(64)
- #define MSEC_TO_HZ_MUL32 U64_C(0x83126e98)
- #define MSEC_TO_HZ_ADJ32 U64_C(0xfdf3b645)
- #define MSEC_TO_HZ_SHR32 32
- #define MSEC_TO_HZ_NUM U64_C(64)
- #define MSEC_TO_HZ_DEN U64_C(125)
- #define HZ_TO_USEC_MUL32 U64_C(0xf4240000)
- #define HZ_TO_USEC_ADJ32 U64_C(0x1c0000)
- #define HZ_TO_USEC_SHR32 21
- #define HZ_TO_USEC_NUM U64_C(15625)
- #define HZ_TO_USEC_DEN U64_C(8)
- #define USEC_TO_HZ_MUL32 U64_C(0x8637bd06)
- #define USEC_TO_HZ_ADJ32 U64_C(0x3ffef39085f)
- #define USEC_TO_HZ_SHR32 42
- #define USEC_TO_HZ_NUM U64_C(8)
- #define USEC_TO_HZ_DEN U64_C(15625)
- #endif /* KERNEL_TIMECONST_H */
- /* -------------------------------------------------------------------- */
因此,下次如果修改了HZ的值,而这个值是perl脚本支持的,但却报类似的错:
- In file included from kernel/time.c:45:
- kernel/timeconst.h:11:2: error: #error "kernel/timeconst.h has the wrong HZ value!"
- make[1]: *** [kernel/time.o] Error 1
- make: *** [kernel] Error 2
- make: *** Waiting for unfinished jobs....
那就要手动执行以下这个perl脚本了。而对于这个HZ值与您的系统的性能关系,还需要仔细斟酌,我目前的项目也遇到了类似的问题,可能有关,继续研究。
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