sysinfo.c
/*********************************************************************** * Some values in /proc are expressed in units of 1/HZ seconds, where HZ * is the kernel clock tick rate. One of these units is called a jiffy. * The HZ value used in the kernel may vary according to hacker desire. * According to Linus Torvalds, this is not true. He considers the values * in /proc as being in architecture-dependant units that have no relation * to the kernel clock tick rate. Examination of the kernel source code * reveals that opinion as wishful thinking. * * In any case, we need the HZ constant as used in /proc. (the real HZ value * may differ, but we don't care) There are several ways we could get HZ: * * 1. Include the kernel header file. If it changes, recompile this library. * 2. Use the sysconf() function. When HZ changes, recompile the C library! * 3. Ask the kernel. This is obviously correct... * * Linus Torvalds won't let us ask the kernel, because he thinks we should * not know the HZ value. Oh well, we don't have to listen to him. * Someone smuggled out the HZ value. :-) * * This code should work fine, even if Linus fixes the kernel to match his * stated behavior. The code only fails in case of a partial conversion. * * Recent update: on some architectures, the 2.4 kernel provides an * ELF note to indicate HZ. This may be for ARM or user-mode Linux * support. This ought to be investigated. Note that sysconf() is still * unreliable, because it doesn't return an error code when it is * used with a kernel that doesn't support the ELF note. On some other * architectures there may be a system call or sysctl() that will work. */ unsigned long long Hertz; static void old_Hertz_hack(void){ unsigned long long user_j, nice_j, sys_j, other_j; /* jiffies (clock ticks) */ double up_1, up_2, seconds; unsigned long long jiffies; unsigned h; char *restrict savelocale; savelocale = setlocale(LC_NUMERIC, NULL); setlocale(LC_NUMERIC, "C"); do{ FILE_TO_BUF(UPTIME_FILE,uptime_fd); sscanf(buf, "%lf", &up_1); /* uptime(&up_1, NULL); */ FILE_TO_BUF(STAT_FILE,stat_fd); sscanf(buf, "cpu %Lu %Lu %Lu %Lu", &user_j, &nice_j, &sys_j, &other_j); FILE_TO_BUF(UPTIME_FILE,uptime_fd); sscanf(buf, "%lf", &up_2); /* uptime(&up_2, NULL); */ } while((long long)( (up_2-up_1)*1000.0/up_1 )); /* want under 0.1% error */ setlocale(LC_NUMERIC, savelocale); jiffies = user_j + nice_j + sys_j + other_j; seconds = (up_1 + up_2) / 2; h = (unsigned)( (double)jiffies/seconds/smp_num_cpus ); /* actual values used by 2.4 kernels: 32 64 100 128 1000 1024 1200 */ switch(h){ case 9 ... 11 : Hertz = 10; break; /* S/390 (sometimes) */ case 18 ... 22 : Hertz = 20; break; /* user-mode Linux */ case 30 ... 34 : Hertz = 32; break; /* ia64 emulator */ case 48 ... 52 : Hertz = 50; break; case 58 ... 61 : Hertz = 60; break; case 62 ... 65 : Hertz = 64; break; /* StrongARM /Shark */ case 95 ... 105 : Hertz = 100; break; /* normal Linux */ case 124 ... 132 : Hertz = 128; break; /* MIPS, ARM */ case 195 ... 204 : Hertz = 200; break; /* normal << 1 */ case 253 ... 260 : Hertz = 256; break; case 393 ... 408 : Hertz = 400; break; /* normal << 2 */ case 790 ... 808 : Hertz = 800; break; /* normal << 3 */ case 990 ... 1010 : Hertz = 1000; break; /* ARM */ case 1015 ... 1035 : Hertz = 1024; break; /* Alpha, ia64 */ case 1180 ... 1220 : Hertz = 1200; break; /* Alpha */ default: #ifdef HZ Hertz = (unsigned long long)HZ; /* <asm/param.h> */ #else /* If 32-bit or big-endian (not Alpha or ia64), assume HZ is 100. */ Hertz = (sizeof(long)==sizeof(int) || htons(999)==999) ? 100UL : 1024UL; #endif fprintf(stderr, "Unknown HZ value! (%d) Assume %Ld.\n", h, Hertz); } } |
[링크 : http://lkml.iu.edu/hypermail/linux/kernel/0401.2/0065.html]
[링크 : http://forum.buffalo.nas-central.org/viewtopic.php?f=18&t=13451]
[링크 : http://procps.sourceforge.net/]
[링크 : https://bugs.launchpad.net/ubuntu/+source/procps/+bug/364656]
[링크 : https://launchpadlibrarian.net/29934773/procps_3.2.7-11ubuntu3.debdiff.gz]
[링크 : https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=460331]
[링크 : https://lkml.org/lkml/2002/2/18/187]
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