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An Go library of synchronization primitives to help make use of hardware transactional memory (HTM)
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README.md

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SafetyFast - Put thread-safety first, with the performance of safety last.

This is a Go library that implements synchronization primitives over Intel TSX (hardware transactional primitives).

go get github.com/linux4life798/safetyfast

Checkout the SafetyFast Project Page.

Benchmarking

The following plot shows the number of milliseconds it took for 8 goroutines to increments 480000 random elements (per goroutine) of an array of ints. The x axis denotes how large (and therefore sparse) the array was. The synchronization primitive used during the increment is indicated as a series/line.

Performance Graph

Note that, as the array size increases, the likelihood of two goroutines touching the same element at the same instance decreases. This is why we see such a dramatic increase in speed, when using either the HLE or RTM style synchronization primitive.

The SystemMutex is just sync.Mutex.

It is also worth observing that the performance started to degrade towards the very large array sizes. This is most likely due to a cache size limitation.

Snippets

Using RTM

m := map[string]int{
    "word1": 0,
}

c := NewRTMContexDefault()
c.Atomic(func() {
    // Action to be done transactionally
    m["word1"] = m["word1"] + 1
})

Using HLE

m := map[string]int{
    "word1": 0,
}

var lock safetyfast.SpinHLEMutex
lock.Lock()
// Action to be done transactionally
m["word1"] = m["word1"] + 1
lock.Unlock()


Check if your CPU supports Intel TSX

Use the doihavetsx utility

go get github.com/linux4life798/safetyfast/doihavetsx
doihavetsx

The output should look something like:

CPU Brand:  Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz
RTM:        Yes
HLE:        Yes

Common CPUs and Machines

CPU Name CPU Codename / Generation TSX Supported Machine Description
Intel(R) Xeon(R) CPU E3-1505M v5 @ 2.80GHz Skylake/6th Yes Dell Precision 5510
Intel(R) Core(TM) i7-3720QM CPU @ 2.60GHz Ivy Bridge/3rd No MacBook Pro (Retina, Mid 2012)
Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz Kaby Lake/7th Yes MacBook Pro "Core i7" 2.9 15" Touch/Mid-2017
Intel(R) Core(TM) i7-4650U CPU @ 1.70GHz Haswell/4th No (Yes-before microcode install) MacBook Air (13-inch, Early 2014)
Intel(R) Core(TM) i7-7Y75 CPU @ 1.30GHz Kaby Lake/7th Yes MacBook (Retina, 12-inch, 2017)
Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz Haswell/4th No MacBook Pro (Retina, 15-inch, Mid 2015)
Intel(R) Core(TM) i7-7920HQ CPU @ 3.10GHz Kaby Lake/7th Yes MacBook Pro (15-inch, 2017)

Please add your machine to this table! Pull-request or issues welcome.



Code Examples

Checking for HLE and RTM support in code

It is necessary to check that the CPU you are using support Intel RTM and/or Intel HLE instruction sets, since safetyfast does not check. This can be accomplished by using the Intel provided cpuid package, as shown below.

import (
  "github.com/intel-go/cpuid"
)

func main() {
	if !cpuid.HasExtendedFeature(cpuid.RTM) {
		panic("The CPU does not support Intel RTM")
	}

	if !cpuid.HasExtendedFeature(cpuid.HLE) {
		panic("The CPU does not support Intel HLE")
	}
}

Using RTM

package main

import (
    "fmt"
    "sync"
    "github.com/linux4life798/safetyfast"
)

func main() {
    m := map[string]int{
        "word1": 0,
        "word2": 0,
    }

    c := safetyfast.NewRTMContexDefault()
    var wg sync.WaitGroup

    wg.Add(2)
    go c.Atomic(func() {
        // Action to be done transactionally
        m["word1"] = m["word1"] + 1
        wg.Done()
    })
    go c.Atomic(func() {
        // Action to be done transactionally
        m["word1"] = m["word1"] + 1
        wg.Done()
    })
    wg.Wait()

    fmt.Println("word1 =", m["word1"])
}

Using HLE

package main

import (
    "fmt"
    "sync"
    "github.com/linux4life798/safetyfast"
)

func main() {
    m := map[string]int{
        "word1": 0,
        "word2": 0,
    }

    var lock safetyfast.SpinHLEMutex
    var wg sync.WaitGroup

    wg.Add(2)
    go func() {
        lock.Lock()
        // Action to be done transactionally
        m["word1"] = m["word1"] + 1
        lock.Unlock()
        wg.Done()
    }()
    go func() {
        lock.Lock()
        // Action to be done transactionally
        m["word1"] = m["word1"] + 1
        lock.Unlock()
        wg.Done()
    }()
    wg.Wait()

    fmt.Println("word1 =", m["word1"])
}
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