├── LICENSE ├── Makefile ├── Readme.md ├── tsc.c └── tsc.h /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 2, June 1991 3 | 4 | Copyright (C) 1989, 1991 Free Software Foundation, Inc., 5 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 6 | Everyone is permitted to copy and distribute verbatim copies 7 | of this license document, but changing it is not allowed. 8 | 9 | Preamble 10 | 11 | The licenses for most software are designed to take away your 12 | freedom to share and change it. By contrast, the GNU General Public 13 | License is intended to guarantee your freedom to share and change free 14 | software--to make sure the software is free for all its users. This 15 | General Public License applies to most of the Free Software 16 | Foundation's software and to any other program whose authors commit to 17 | using it. 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Of course, the commands you use may 322 | be called something other than `show w' and `show c'; they could even be 323 | mouse-clicks or menu items--whatever suits your program. 324 | 325 | You should also get your employer (if you work as a programmer) or your 326 | school, if any, to sign a "copyright disclaimer" for the program, if 327 | necessary. Here is a sample; alter the names: 328 | 329 | Yoyodyne, Inc., hereby disclaims all copyright interest in the program 330 | `Gnomovision' (which makes passes at compilers) written by James Hacker. 331 | 332 | {signature of Ty Coon}, 1 April 1989 333 | Ty Coon, President of Vice 334 | 335 | This General Public License does not permit incorporating your program into 336 | proprietary programs. If your program is a subroutine library, you may 337 | consider it more useful to permit linking proprietary applications with the 338 | library. If this is what you want to do, use the GNU Lesser General 339 | Public License instead of this License. 340 | 341 | -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- 1 | # 2 | # makefile 3 | PROJECT=tsc 4 | SRCS=tsc.c 5 | INCL=tsc.h 6 | CFLAGS=-g -Wall 7 | LIBS=-lrt -lm -lpthread 8 | 9 | all: $(PROJECT) 10 | 11 | $(PROJECT): $(SRCS) $(INCL) 12 | gcc $(CFLAGS) -DTEST_TSC -DTSC_VERBOSE -o $(PROJECT) $(SRCS) $(LIBS) 13 | 14 | clean: 15 | rm -f $(PROJECT) *~ *.o 16 | -------------------------------------------------------------------------------- /Readme.md: -------------------------------------------------------------------------------- 1 | # Convert Intel TSC to nanoseconds 2 | 3 | This is a test/demonstration program that shows the use of the rdtscp instruction under linux, 4 | and how to convert from cycles to nanoseconds for a subset of intel architecture processors. 5 | 6 | There are lots of ways it could go wrong, most of which don't apply to server processors of 7 | the type I use. For more information see http://blog.tinola.com/ 8 | 9 | 10 | 11 | 12 | -------------------------------------------------------------------------------- /tsc.c: -------------------------------------------------------------------------------- 1 | #define _GNU_SOURCE 2 | #include 3 | #include 4 | #include 5 | #include 6 | #include 7 | #include 8 | #include 9 | #include 10 | 11 | #include "tsc.h" 12 | 13 | struct processor_type_s tsc_processor_types[] = { 14 | { "Too Old/Unknown", 100000u }, 15 | { "Nehalem", 133330u }, 16 | { "Westmere", 133330u }, 17 | { "Sandybridge", 100000u }, 18 | { "Ivybridge", 100000u }, 19 | { "Haswell", 100000u }, 20 | { "Broadwell", 100000u }, 21 | { "Skylake", 100000u }, 22 | { "Xeon Phi", 100000u } 23 | }; 24 | 25 | 26 | // ------------------- 27 | // 28 | // TSC functions. 29 | // 30 | // requires a processor that supports the RDTSCP instruction. Or, use LFENCE; RDTSC 31 | // We can extract the socket and cpu we actually ran on from %ECX. 32 | // Intel Instruction Set reference. Vol 2B - 4-304. 33 | // 34 | // returns cycles from the expected cpu. 35 | uint64_t rdtscp(uint32_t expected_cpu) 36 | { 37 | uint32_t lo, hi, cpuid; 38 | #ifdef PARANOID_TSC 39 | uint32_t core, socket; 40 | #endif 41 | __asm__ __volatile__ ("rdtscp" : "=a" (lo), "=d" (hi), "=c" (cpuid)::); 42 | #ifdef PARANOID_TSC 43 | socket = (cpuid & 0xfff000)>>12; 44 | core = cpuid & 0xfff; 45 | if (core != expected_cpu) return -1; 46 | #endif 47 | return (uint64_t)hi << 32 | lo; 48 | } 49 | // 50 | // return the family and model in a single 32 bit integer. 51 | // Family 06 = the ones we're interested in. Family 15 = netburst xeons. 52 | // See; 53 | // https://software.intel.com/en-us/articles/intel-architecture-and-processor-identification-with-cpuid-model-and-family-numbers 54 | // and intel architecture developers manual. 55 | // 56 | static __inline__ uint32_t get_intel_family_model() 57 | { 58 | uint32_t model_register, model, family; 59 | int eax = 1; 60 | 61 | __asm__ __volatile__ ("cpuid" : "=a" (model_register): "a" (eax): "%ebx", "%ecx", "%edx"); 62 | 63 | model = ((model_register & 0xff) >> 4) | ((model_register & 0xf0000) >> 12); 64 | family = ((model_register & 0xf00) >> 8) | ((model_register & 0xff00000) >> 16); 65 | return (family << 16) | model; 66 | } 67 | 68 | // used to determine if we have a 133.33 mhz or 100.00 mhz bclk. 69 | int get_processor_type(uint32_t family_model) 70 | { 71 | switch (family_model) { 72 | // nehalem - Section 35.5 Vol 3c 73 | case 0x6001a: 74 | case 0x6001e: 75 | case 0x6001f: 76 | case 0x6002e: 77 | return NEHALEM; 78 | // westmere - section 35.6 79 | case 0x60025: 80 | case 0x6002c: 81 | case 0x6002f: 82 | return WESTMERE; 83 | // sandy bridge - section 35.8 84 | case 0x6002a: 85 | case 0x6002d: 86 | return SANDYBRIDGE; 87 | case 0x6003a: 88 | case 0x6003e: 89 | return IVYBRIDGE; 90 | case 0x6003c: 91 | case 0x6003f: 92 | case 0x60045: 93 | case 0x60046: 94 | return HASWELL; 95 | case 0x6003d: 96 | case 0x60047: 97 | case 0x6004f: 98 | case 0x60056: 99 | return BROADWELL; 100 | case 0x6004e: 101 | case 0x6005e: 102 | return SKYLAKE; 103 | case 0x60057: 104 | return PHI; 105 | default: 106 | return TOO_OLD; 107 | } 108 | return TOO_OLD; 109 | } 110 | 111 | // read msrs - stolen from cpupower helpers 112 | // http://lxr.free-electrons.com/source/tools/power/cpupower/utils/helpers/msr.c#L26 113 | // 114 | int read_msr(int cpu, unsigned int idx, uint64_t *val) 115 | { 116 | int fd; 117 | char msr_file_name[64]; 118 | 119 | sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu); 120 | fd = open(msr_file_name, O_RDONLY); 121 | if (fd < 0) return -1; 122 | if (lseek(fd, idx, SEEK_CUR) == -1) goto err; 123 | if (read(fd, val, sizeof *val) != sizeof *val) goto err; 124 | close(fd); 125 | return 0; 126 | err: 127 | close(fd); 128 | return -1; 129 | } 130 | // 0xce is the intel MSR_PLATFORM_INFO. 131 | // SandyBridge or later (IvyBridge, Haswell) is a 100mhz clock. Nehalem/Westmere is a 133.33Mhz baseclock 132 | // See section 35. 133 | // 134 | // There are some caveats. This is only supported on recent processor families. 135 | // 136 | // Also, if the motherboard manufacturer messes about with the BCLK then the base_clock will be wrong. 137 | // 138 | uint32_t get_tsc_freq_khz(cpu) 139 | { 140 | uint64_t platform_info, non_turbo_ratio; 141 | int processor_type; 142 | 143 | processor_type = get_processor_type(get_intel_family_model()); 144 | 145 | #ifdef TSC_VERBOSE 146 | printf ("Detected processor with family/model of %x\n",get_intel_family_model()); 147 | printf ("This is a %s processor with a base clock of %dkhz\n", tsc_processor_types[processor_type].name, tsc_processor_types[processor_type].base_clock_khz); 148 | #endif 149 | if (processor_type == TOO_OLD) { 150 | fprintf(stderr,"processor too new, too old, or not detected\n"); 151 | return -1; 152 | } 153 | 154 | if (read_msr(cpu,0xce, &platform_info) == -1) { 155 | fprintf(stderr,"error reading MSR_PLATFORM_INFO - Are you running this as root?\n"); 156 | return -1; 157 | } 158 | non_turbo_ratio = (platform_info & 0xff00) >> 8; 159 | return non_turbo_ratio * tsc_processor_types[processor_type].base_clock_khz; 160 | } 161 | 162 | // See comment for the math behind this in arch/x86/kernel/tsc.c 163 | // http://lxr.free-electrons.com/source/arch/x86/kernel/tsc.c?v=3.18#L157 164 | // 165 | uint32_t get_cycles_to_nsec_scale(unsigned int tsc_frequency_khz) 166 | { 167 | return (uint32_t)((1000000)<<10 )/(uint32_t)tsc_frequency_khz; 168 | } 169 | 170 | uint64_t cycles_to_nsec(uint64_t cycles, uint32_t scale_factor) 171 | { 172 | return (cycles * scale_factor) >> 10; 173 | } 174 | // 175 | // TSC Routines 176 | // ------- 177 | 178 | #ifdef TEST_TSC 179 | pid_t gettid(void) { return syscall(SYS_gettid); } // not in libc apparently 180 | 181 | 182 | // This needs to run as root. 183 | int main (int argc, char *argv[]) 184 | { 185 | cpu_set_t cpuset; 186 | uint32_t cycles_nsec_scale, tsc_freq_khz; 187 | uint64_t start_timestamp, end_timestamp, cycles; 188 | int cpu; 189 | 190 | if (argc < 2) { 191 | fprintf (stderr,"./tsc \ne.g ./tsc 47\nwill pin to cpu47 and then run a simple timing loop to test tsc and cpu family ident\n"); 192 | exit (0); 193 | } 194 | 195 | cpu = atoi(argv[1]); 196 | 197 | CPU_ZERO(&cpuset); 198 | CPU_SET(cpu,&cpuset); 199 | 200 | // set our cpu affinity. Ideally onto an isolated cpu. 201 | if (sched_setaffinity(gettid(),sizeof(cpu_set_t), &cpuset) != 0) { 202 | fprintf(stderr,"Thread %d: failed to set affinity to cpu %d. Reason was %s\n",gettid(),cpu,strerror(errno)); 203 | exit(0); 204 | } 205 | 206 | // Get the MSR's idea of the TSC tick rate in khz 207 | tsc_freq_khz = get_tsc_freq_khz(cpu); 208 | 209 | // convert this into a scale factor 210 | cycles_nsec_scale = get_cycles_to_nsec_scale(tsc_freq_khz); 211 | printf("Invariant TSC runs at %u kHz, scale factor %u\n",tsc_freq_khz, cycles_nsec_scale); 212 | 213 | // simple timing exercise to see if we're close to reality 214 | start_timestamp = rdtscp(cpu); 215 | usleep(500000); 216 | end_timestamp = rdtscp(cpu); 217 | 218 | // The difference in timestamp cycles, converted to nanoseconds via the scale factor. 219 | cycles = (end_timestamp-start_timestamp); 220 | printf ("Expected to sleep for %u nanos, actually slept for %Lu cycles, %Lu nanos\n", (500000*1000), (unsigned long long)cycles, (unsigned long long)cycles_to_nsec(cycles, cycles_nsec_scale)); 221 | 222 | return 0; 223 | } 224 | #endif 225 | -------------------------------------------------------------------------------- /tsc.h: -------------------------------------------------------------------------------- 1 | // tsc.h 2 | #include 3 | #include 4 | 5 | // 6 | // check cpu we executed on was the one expected. Turn off for speed. 7 | #define PARANOID_TSC 1 8 | // 9 | // Print out processor id information 10 | //#define TSC_VERBOSE 1 11 | // 12 | // Run as a stand alone program for testing 13 | //#define TEST_TSC 1 14 | // 15 | // Identification for setting the bclk rate 16 | // 17 | enum { 18 | TOO_OLD, 19 | NEHALEM, 20 | WESTMERE, 21 | SANDYBRIDGE, 22 | IVYBRIDGE, 23 | HASWELL, 24 | BROADWELL, 25 | SKYLAKE, 26 | PHI 27 | } processor_enum; 28 | 29 | struct processor_type_s { 30 | char *name; 31 | unsigned int base_clock_khz; 32 | }; 33 | 34 | extern struct processor_type_s tsc_processor_types[]; 35 | 36 | // prototypes 37 | /* tsc.c */ 38 | uint64_t rdtscp(uint32_t expected_cpu); 39 | int get_processor_type(uint32_t family_model); 40 | int read_msr(int cpu, unsigned int idx, uint64_t *val); 41 | uint32_t get_tsc_freq_khz(int cpu); 42 | uint32_t get_cycles_to_nsec_scale(unsigned int tsc_frequency_khz); 43 | uint64_t cycles_to_nsec(uint64_t cycles, uint32_t scale_factor); 44 | --------------------------------------------------------------------------------