From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 30 May 2001 23:41:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 30 May 2001 23:40:52 -0400 Received: from saturn.cs.uml.edu ([129.63.8.2]:28427 "EHLO saturn.cs.uml.edu") by vger.kernel.org with ESMTP id ; Wed, 30 May 2001 23:40:43 -0400 From: "Albert D. Cahalan" Message-Id: <200105310340.f4V3eVF244481@saturn.cs.uml.edu> Subject: Re: How to know HZ from userspace? To: laforge@gnumonks.org (Harald Welte) Date: Wed, 30 May 2001 23:40:30 -0400 (EDT) Cc: linux-kernel@vger.kernel.org In-Reply-To: <20010530203725.H27719@corellia.laforge.distro.conectiva> from "Harald Welte" at May 30, 2001 08:37:25 PM X-Mailer: ELM [version 2.5 PL2] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Harald Welte writes: > Is there any way to read out the compile-time HZ value of the kernel? > > I had a brief look at /proc/* and didn't find anything. Look again, this time with a sick mind. Got your barf bag? Kubys made me do it. /****************************************************************/ /***********************************************************************\ * Copyright (C) 1992-1998 by Michael K. Johnson, johnsonm@redhat.com * * * * This file is placed under the conditions of the GNU Library * * General Public License, version 2, or any later version. * * See file COPYING for information on distribution conditions. * \***********************************************************************/ /* ...but Albert Cahalan wrote the really evil parts. MKJ is only guilty for the macro */ /* Sets Hertz equal to the kernel's HZ, as seen in /proc. */ #include #include #include #include #include #include #ifndef HZ #include /* htons */ #endif long smp_num_cpus; /* number of CPUs */ #define BAD_OPEN_MESSAGE \ "Error: /proc must be mounted\n" \ " To mount /proc at boot you need an /etc/fstab line like:\n" \ " /proc /proc proc defaults\n" \ " In the meantime, mount /proc /proc -t proc\n" #define STAT_FILE "/proc/stat" static int stat_fd = -1; #define UPTIME_FILE "/proc/uptime" static int uptime_fd = -1; #define LOADAVG_FILE "/proc/loadavg" static int loadavg_fd = -1; #define MEMINFO_FILE "/proc/meminfo" static int meminfo_fd = -1; static char buf[1024]; /* This macro opens filename only if necessary and seeks to 0 so * that successive calls to the functions are more efficient. * It also reads the current contents of the file into the global buf. */ #define FILE_TO_BUF(filename, fd) do{ \ static int local_n; \ if (fd == -1 && (fd = open(filename, O_RDONLY)) == -1) { \ fprintf(stderr, BAD_OPEN_MESSAGE); \ fflush(NULL); \ _exit(102); \ } \ lseek(fd, 0L, SEEK_SET); \ if ((local_n = read(fd, buf, sizeof buf - 1)) < 0) { \ perror(filename); \ fflush(NULL); \ _exit(103); \ } \ buf[local_n] = '\0'; \ }while(0) unsigned long Hertz; static void init_Hertz_value(void) __attribute__((constructor)); static void init_Hertz_value(void){ unsigned long user_j, nice_j, sys_j, other_j; /* jiffies (clock ticks) */ double up_1, up_2, seconds; unsigned long jiffies, h; smp_num_cpus = sysconf(_SC_NPROCESSORS_CONF); if(smp_num_cpus==-1) smp_num_cpus=1; 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)( (up_2-up_1)*1000.0/up_1 )); /* want under 0.1% error */ jiffies = user_j + nice_j + sys_j + other_j; seconds = (up_1 + up_2) / 2; h = (unsigned long)( (double)jiffies/seconds/smp_num_cpus ); /* actual values used by 2.4 kernels: 32 64 100 128 1000 1024 1200 */ switch(h){ case 30 ... 34 : Hertz = 32; break; /* ia64 emulator */ case 48 ... 52 : Hertz = 50; break; case 58 ... 62 : Hertz = 60; break; case 63 ... 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)HZ; /* */ #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! (%ld) Assume %ld.\n", h, Hertz); } } /****************************************************************/