Re: [go-nuts] when do you use sync.Mutex instead of sync.RWMutex

[김용빈]

thank you all for the great answers.

now I know when I should use "RWMutex" instead of "Mutex". ;)

2020년 12월 21일 월요일 오전 1시 44분 1초 UTC+9에 mar...@gmail.com님이 작성:

> Code using a simple sync.Mutex is also simpler, since you only have one 
> way to lock and unlock and you don't have to think about lock type when 
> writing code. In my opinion, use sync.Mutex, and if it proves to be 
> inefficient, start investigating alternatives. In most cases, your simple 
> code will work well enough. It's much more important to keep your critical 
> sections small and quick than tweaking mutex behavior.
>
> As others have said, RWMutex is great for cache-like things, but could 
> actually work poorly in other access patterns.
>
> On Sun, Dec 20, 2020 at 4:16 AM Robert Engels  
> wrote:
>
>> A cache almost always uses a RW mutex or a lock free technique like copy 
>> on write/CAS to avoid contention. 
>>
>> A simple mutex is fine for less performance critical code with guaranteed 
>> exclusive/sequential access needs. Many transaction modes are implemented 
>> with a simple lock/mutex. 
>>
>> On Dec 20, 2020, at 6:59 AM, 'Axel Wagner' via golang-nuts <
>> golan...@googlegroups.com> wrote:
>>
>> 
>> Unless I specifically know that a variable will be written rarely and 
>> read often, I tend to use `Mutex`. I'm too worried that the preferential 
>> treatment of write-locks in an `RWMutex` leads to surprising 
>> contention-issues if there isn't an overwhelming relationship between their 
>> frequencies. I also assume - given that it has the more complicated 
>> semantics - that a `Mutex` is generally cheaper than an `RWMutex`, all 
>> things being equal.
>>
>> So I tend to handle it the exact opposite of what you suggest - unless I 
>> have a specific reason to use `RWMutex`, I default to `Mutex`.
>>
>> On Sun, Dec 20, 2020 at 9:44 AM 김용빈  wrote:
>>
>>> we usually both read and write for a value. not only read, nor write.
>>>
>>> with that, I feel RWMutex is always right choice.
>>>
>>> when should I use Mutex instead of RWMutex?
>>>
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>> 
>> .
>>
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Re: [go-nuts] when do you use sync.Mutex instead of sync.RWMutex

[Marcin Romaszewicz]

Code using a simple sync.Mutex is also simpler, since you only have one way
to lock and unlock and you don't have to think about lock type when writing
code. In my opinion, use sync.Mutex, and if it proves to be inefficient,
start investigating alternatives. In most cases, your simple code will work
well enough. It's much more important to keep your critical sections small
and quick than tweaking mutex behavior.

As others have said, RWMutex is great for cache-like things, but could
actually work poorly in other access patterns.

On Sun, Dec 20, 2020 at 4:16 AM Robert Engels  wrote:

> A cache almost always uses a RW mutex or a lock free technique like copy
> on write/CAS to avoid contention.
>
> A simple mutex is fine for less performance critical code with guaranteed
> exclusive/sequential access needs. Many transaction modes are implemented
> with a simple lock/mutex.
>
> On Dec 20, 2020, at 6:59 AM, 'Axel Wagner' via golang-nuts <
> golang-nuts@googlegroups.com> wrote:
>
> 
> Unless I specifically know that a variable will be written rarely and read
> often, I tend to use `Mutex`. I'm too worried that the preferential
> treatment of write-locks in an `RWMutex` leads to surprising
> contention-issues if there isn't an overwhelming relationship between their
> frequencies. I also assume - given that it has the more complicated
> semantics - that a `Mutex` is generally cheaper than an `RWMutex`, all
> things being equal.
>
> So I tend to handle it the exact opposite of what you suggest - unless I
> have a specific reason to use `RWMutex`, I default to `Mutex`.
>
> On Sun, Dec 20, 2020 at 9:44 AM 김용빈  wrote:
>
>> we usually both read and write for a value. not only read, nor write.
>>
>> with that, I feel RWMutex is always right choice.
>>
>> when should I use Mutex instead of RWMutex?
>>
>> --
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>> 
>> .
>>
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>

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Re: [go-nuts] when do you use sync.Mutex instead of sync.RWMutex

[Robert Engels]

A cache almost always uses a RW mutex or a lock free technique like copy on 
write/CAS to avoid contention. 

A simple mutex is fine for less performance critical code with guaranteed 
exclusive/sequential access needs. Many transaction modes are implemented with 
a simple lock/mutex. 

> On Dec 20, 2020, at 6:59 AM, 'Axel Wagner' via golang-nuts 
>  wrote:
> 
> 
> Unless I specifically know that a variable will be written rarely and read 
> often, I tend to use `Mutex`. I'm too worried that the preferential treatment 
> of write-locks in an `RWMutex` leads to surprising contention-issues if there 
> isn't an overwhelming relationship between their frequencies. I also assume - 
> given that it has the more complicated semantics - that a `Mutex` is 
> generally cheaper than an `RWMutex`, all things being equal.
> 
> So I tend to handle it the exact opposite of what you suggest - unless I have 
> a specific reason to use `RWMutex`, I default to `Mutex`.
> 
>> On Sun, Dec 20, 2020 at 9:44 AM 김용빈  wrote:
>> we usually both read and write for a value. not only read, nor write.
>> 
>> with that, I feel RWMutex is always right choice.
>> 
>> when should I use Mutex instead of RWMutex?
>> -- 
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>> "golang-nuts" group.
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> 
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Re: [go-nuts] when do you use sync.Mutex instead of sync.RWMutex

['Axel Wagner' via golang-nuts]

Unless I specifically know that a variable will be written rarely and read
often, I tend to use `Mutex`. I'm too worried that the preferential
treatment of write-locks in an `RWMutex` leads to surprising
contention-issues if there isn't an overwhelming relationship between their
frequencies. I also assume - given that it has the more complicated
semantics - that a `Mutex` is generally cheaper than an `RWMutex`, all
things being equal.

So I tend to handle it the exact opposite of what you suggest - unless I
have a specific reason to use `RWMutex`, I default to `Mutex`.

On Sun, Dec 20, 2020 at 9:44 AM 김용빈  wrote:

> we usually both read and write for a value. not only read, nor write.
>
> with that, I feel RWMutex is always right choice.
>
> when should I use Mutex instead of RWMutex?
>
> --
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> "golang-nuts" group.
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> 
> .
>

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Re: [go-nuts] when do you use sync.Mutex instead of sync.RWMutex

[Gregor Best]

An RWMutex will block all new readers if a writer is waiting to acquire 
the lock, and that writer will only acquire the lock once all current 
readers are gone.


Depending on the semantics of your application and the frequency of 
writes, that might constrain the throughput through the section 
protected by the lock to the rate of writes, especially if the rate of 
writes and the attempts to acquire the mutex for reading are roughly in 
the same order of magnitude.


On 20.12.20 09:44, 김용빈 wrote:

we usually both read and write for a value. not only read, nor write.

with that, I feel RWMutex is always right choice.

when should I use Mutex instead of RWMutex?

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.


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  Gregor Best
  b...@pferdewetten.de

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[go-nuts] when do you use sync.Mutex instead of sync.RWMutex

[김용빈]

we usually both read and write for a value. not only read, nor write.

with that, I feel RWMutex is always right choice.

when should I use Mutex instead of RWMutex?

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