138 lines
4 KiB
Markdown
138 lines
4 KiB
Markdown
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# cpuid
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Package cpuid provides information about the CPU running the current program.
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CPU features are detected on startup, and kept for fast access through the life of the application.
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Currently x86 / x64 (AMD64/i386) and ARM (ARM64) is supported, and no external C (cgo) code is used, which should make the library very easy to use.
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You can access the CPU information by accessing the shared CPU variable of the cpuid library.
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Package home: https://github.com/klauspost/cpuid
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[](https://pkg.go.dev/github.com/klauspost/cpuid/v2)
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[![Build Status][3]][4]
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[3]: https://travis-ci.org/klauspost/cpuid.svg?branch=master
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[4]: https://travis-ci.org/klauspost/cpuid
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## installing
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`go get -u github.com/klauspost/cpuid/v2` using modules.
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Drop `v2` for others.
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## example
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```Go
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package main
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import (
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"fmt"
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"strings"
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. "github.com/klauspost/cpuid/v2"
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)
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func main() {
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// Print basic CPU information:
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fmt.Println("Name:", CPU.BrandName)
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fmt.Println("PhysicalCores:", CPU.PhysicalCores)
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fmt.Println("ThreadsPerCore:", CPU.ThreadsPerCore)
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fmt.Println("LogicalCores:", CPU.LogicalCores)
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fmt.Println("Family", CPU.Family, "Model:", CPU.Model, "Vendor ID:", CPU.VendorID)
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fmt.Println("Features:", fmt.Sprintf(strings.Join(CPU.FeatureSet(), ",")))
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fmt.Println("Cacheline bytes:", CPU.CacheLine)
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fmt.Println("L1 Data Cache:", CPU.Cache.L1D, "bytes")
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fmt.Println("L1 Instruction Cache:", CPU.Cache.L1D, "bytes")
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fmt.Println("L2 Cache:", CPU.Cache.L2, "bytes")
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fmt.Println("L3 Cache:", CPU.Cache.L3, "bytes")
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fmt.Println("Frequency", CPU.Hz, "hz")
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// Test if we have these specific features:
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if CPU.Supports(SSE, SSE2) {
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fmt.Println("We have Streaming SIMD 2 Extensions")
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}
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}
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```
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Sample output:
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```
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>go run main.go
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Name: AMD Ryzen 9 3950X 16-Core Processor
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PhysicalCores: 16
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ThreadsPerCore: 2
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LogicalCores: 32
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Family 23 Model: 113 Vendor ID: AMD
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Features: ADX,AESNI,AVX,AVX2,BMI1,BMI2,CLMUL,CMOV,CX16,F16C,FMA3,HTT,HYPERVISOR,LZCNT,MMX,MMXEXT,NX,POPCNT,RDRAND,RDSEED,RDTSCP,SHA,SSE,SSE2,SSE3,SSE4,SSE42,SSE4A,SSSE3
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Cacheline bytes: 64
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L1 Data Cache: 32768 bytes
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L1 Instruction Cache: 32768 bytes
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L2 Cache: 524288 bytes
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L3 Cache: 16777216 bytes
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Frequency 0 hz
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We have Streaming SIMD 2 Extensions
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```
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# usage
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The `cpuid.CPU` provides access to CPU features. Use `cpuid.CPU.Supports()` to check for CPU features.
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A faster `cpuid.CPU.Has()` is provided which will usually be inlined by the gc compiler.
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Note that for some cpu/os combinations some features will not be detected.
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`amd64` has rather good support and should work reliably on all platforms.
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Note that hypervisors may not pass through all CPU features.
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## arm64 feature detection
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Not all operating systems provide ARM features directly
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and there is no safe way to do so for the rest.
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Currently `arm64/linux` and `arm64/freebsd` should be quite reliable.
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`arm64/darwin` adds features expected from the M1 processor, but a lot remains undetected.
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A `DetectARM()` can be used if you are able to control your deployment,
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it will detect CPU features, but may crash if the OS doesn't intercept the calls.
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A `-cpu.arm` flag for detecting unsafe ARM features can be added. See below.
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Note that currently only features are detected on ARM,
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no additional information is currently available.
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## flags
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It is possible to add flags that affects cpu detection.
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For this the `Flags()` command is provided.
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This must be called *before* `flag.Parse()` AND after the flags have been parsed `Detect()` must be called.
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This means that any detection used in `init()` functions will not contain these flags.
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Example:
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```Go
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package main
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import (
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"flag"
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"fmt"
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"strings"
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"github.com/klauspost/cpuid/v2"
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)
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func main() {
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cpuid.Flags()
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flag.Parse()
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cpuid.Detect()
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// Test if we have these specific features:
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if cpuid.CPU.Supports(cpuid.SSE, cpuid.SSE2) {
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fmt.Println("We have Streaming SIMD 2 Extensions")
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}
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}
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```
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# license
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This code is published under an MIT license. See LICENSE file for more information.
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