If you're interested in the CPUID instruction, I can send you a small tool for Linux I'm developing that detects the CPU, the microarchitecture, codename, core stepping and has more sophisticated cache recognition than /proc/cpuinfo for multicore CPUs. Dunno if it's the perfect workaround, but at least I know it works. So I added this in case some guys running hardened gentoo (which uses -fpic AFAIK) try to compile this with their default CFLAGS. It's particularly interesting for shared libraries or making code invulnerable against some exploits because the code's memory adresses are "hidden". We can determine the CPU usage by taking the percentage of time spent idling and subtracting it from 100. CPU Usage can only be measured over a specified interval of time. (I think it's about memory adresses)ĭetails on PIC (Position Independent Code) can be found at. email protected cat /proc/cpuinfo grep core core id : 0 cpu cores : 1 On the other hand, CPU usage is the percentage of time a CPU takes to process non-idle tasks. If you modify the EBX register (or "clobber" it as it's called in assembly) and compile code with the -fpic option of GCC you'll get an error, because the EBX register is supposed to hold some pretty important data. Why did u define a "keeper" named variable and used it in output operands if youre not gonna send it out of the "void cpuid" function ?That "keeper" variable keeps the value of register EBX before executing the CPUID instruction and is used to write that value back after the EAX, EBX, ECX and EDX register values have been saved to *a,*b,*c and *d. }For details on what I'm doing here see or for Intel-specific information. If ( threads > cores ) printf("Hyper-Threading CPU (%i threads, %i core(s))\n",threads,cores) Įlse printf("Multi-core CPU (%i threads, %i cores)\n",threads,cores) Įlse printf("Single-core CPU without hyper-threading (1 thread, 1 core)\n") Here are six ways to get that information on Linux. Int read_val(int *reg, int startbit, int endbit) Sometimes, you need to get information about the CPU on a machine, whether it's because you just can't remember what kind of CPU your computer has or you need a specific detail, such as the number of cores or whether it's 32- or 64-bit. Alternatively, if you are looking for the number of virtual cores, you count the number of times the line cpu cores is found, which is. > cat /proc/cpuinfo grep -m 1 'cpu cores' cpu cores : 2. These assembler instructions are already available as functions in the Linux kernel headers asm/cachetype.h: set_csselr(.Void cpuid(int *a, int *b, int *c, int *d) Thus, if you want to have the number of physical core, you just take the first occurrence of the line cpu cores, which is. In the "Arm® Cortex®-A53 MPCore Processor Technical Reference Manual" is a chapter, "Cache Size Selection Register" and "Cache Size ID Register", including assembler instructions. TODO: Create a minimal C example, lazy now, asked at: How to receive L1, L2 & 元 cache size using CPUID instruction in x86ĪRM also has an architecture-defined mechanism to find cache sizes through registers such as the Cache Size ID Register (CCSIDR), see the ARMv8 Programmers' Manual 11.6 "Cache discovery" for an overview.įor ARM CPUs running Linux (tested on Raspberry Pi 3B+ with Raspbian (32 bit)): I haven't confirmed by step debugging / instruction tracing, but the source for 2.28 sysdeps/x86/cacheinfo.c does that: _cpuid (2, eax, ebx, ecx, edx) It will work no matter what Linux distribution you are using. ![]() Identifying the type of processor using the proc/cpuinfo file does not require installing any additional programs. The CPUID x86 instruction also offers cache information, and can be directly accessed by userland. Get CPU Info in Linux The simplest way to determine what type of CPU you have is by displaying the contents of the /proc/cpuinfo virtual file. The cool thing about this interface is that it is just a wrapper around the POSIX sysconf C function (cache arguments are non-POSIX extensions), and so it can be used from C code as well: long l2 = sysconf(_SC_LEVEL2_CACHE_SIZE) Or for a single level: getconf LEVEL2_CACHE_SIZE
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