Re: Can you write code directly in CIL ???


"Nicholas Paldino [.NET/C# MVP]" <mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:%23YB$FaqCGHA.3820@xxxxxxxxxxxxxxxxxxxxxxx
> Peter,
>
> You are missing the point completely. If you implement your code as
> managed code, even in IL, you can't stop a GC no matter what. Your thread is
> going to be pre-empted (in most situations, except if you have the GC running
> on a separate thread) and it WILL stop and it WILL affect your performance
> when it happens.

I don't care if a GC occurs during the execution of my code. It can't occur
because of my code because my code knows how much memory it needs in advance and
always needs all of this memory the whole time that it is executing. If some
other process interrupts my code, it won't hurt it. My code just can't take more
than 1/10 second to execute, since it needs to execute every second this will
limit its use to 10% of the CPU time. Ultimately I want to limit my thread's
required execution to no more than 10% of the CPU time. This means that this one
function can't take more than 1/10 second to execute.

>
> Just because your code knows how much memory it needs doesn't mean that you
> can pre-empt a GC. If it happens, it's going to happen, and there is nothing
> you can do about it. Your 100-line function isn't going to be able to stop
> it, and the CLR isn't going to care what your function is doing.
>
> You can't just pretend its not going to happen. It does, and it will, and
> you can't stop it. This isn't a choice you have if you are running managed
> code, whether you do it in IL or not.
>
> This is what it means to have ^managed^ code. The CLR is going to provide
> a good number of services, but you are going to have to pay for them, and
> should be aware of how they impact your code.
>
> This is why I recommended that you use interop with your unmanaged code.
> You will have your performance requirements fufilled, and not have to worry
> about doing something that will ultimately be self-defeating.

I don't think that unmanaged code would make a good .NET component. The current
design requires the function to be implemented as a .NET component.

>
> --
> - Nicholas Paldino [.NET/C# MVP]
> - mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> "Peter Olcott" <olcott@xxxxxxx> wrote in message
> news:GV3sf.37927$QW2.2410@xxxxxxxxxxxxx
>>
>> "Nicholas Paldino [.NET/C# MVP]" <mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
>> message news:uvvaatpCGHA.4004@xxxxxxxxxxxxxxxxxxxxxxx
>>> Peter,
>>>
>>> You don't understand a fundamental concept to .NET and CIL. Yes, there
>>> are compilers that will perform optimization of IL to a certain degree.
>>>
>>> However, when the managed code is run, the CLR will take the CIL and then
>>> compile it into native code. At this point in time, it is free to optimize,
>>> or not optimize, or mangle your code in any way you want when making the
>>> transition from CIL to native code.
>>>
>>> When you are dealing with assembly language in general, you have complete
>>> control of what is going on, memory allocation, deallocation, execution,
>>> etc, etc. With the CLR, this is taken out of your hands to a degree.
>>
>> I don't care about these things they are not effecting my performance. What
>> is effecting my performance are things such as the compiler failing to inline
>> my functions code, and unnecessary overhead in the translation of a switch
>> statement. My function will be always executed several million times every
>> second. It must run concurrently with other applications.
>>
>>>
>>> For example, have you considered, what happens when a Garbage Collection
>>> (GC) occurs while your function is running? If it is in complete managed
>>> code, then there is nothing that you can do about it, and your function will
>>> resume running when the GC is complete. Depending on what is happening on
>>> the machine at the time, combined with what your program is doing, etc, etc,
>>> it is very feasible that your code will take more than 1/10th of a second.
>> My code knows exactly how much memory it needs at load time. It needs all of
>> this memory the whole time that it executes. It would make no sense to have
>> any garbage collection of my code's memory in this case. I want my code to be
>> implemented as a .ET component.
>>
>>>
>>> Just because it looks like assembly language, don't assume that CIL is
>>> assembly language. There are some very different things going on under the
>>> hood.
>>>
>>> --
>>> - Nicholas Paldino [.NET/C# MVP]
>>> - mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>
>>> "Peter Olcott" <olcott@xxxxxxx> wrote in message
>>> news:xj2sf.37906$QW2.34052@xxxxxxxxxxxxx
>>>>I want to be able to stick with purely managed code, if possible. I just
>>>>need this 100 line function to run as fast as if it was hand tweaked
>>>>assembly language. I have examined CIL, for the most part it is essentially
>>>>assembly language. From what I understand any optimizations take place
>>>>before the CIL is generated. When I designed this system (in 1998) I had
>>>>hand tweaked assembly language in mind for this crucial function all along.
>>>>
>>>> "Nicholas Paldino [.NET/C# MVP]" <mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
>>>> message news:%23RjK3$oCGHA.2040@xxxxxxxxxxxxxxxxxxxxxxx
>>>>> Peter,
>>>>>
>>>>> Not at all. When the CLR gets a hold of the JIT, it is free to perform
>>>>> any optimizations it deems necessary, and that might not necessarily be in
>>>>> line with what you are expecting.
>>>>>
>>>>> My recommendation would be to use Managed C++ to create a wrapper to
>>>>> your unmanaged code which uses It Just Works (IJW, seriously). You should
>>>>> get a managed interface, and the best possible performance (for this
>>>>> specific situation, not all situations) between managed an unmanaged code.
>>>>>
>>>>>
>>>>> --
>>>>> - Nicholas Paldino [.NET/C# MVP]
>>>>> - mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>>>
>>>>> "Peter Olcott" <olcott@xxxxxxx> wrote in message
>>>>> news:_51sf.37898$QW2.37853@xxxxxxxxxxxxx
>>>>>>I need the best possible execution speed. I have found that there is a
>>>>>>large difference in the quality of the code generated by the various
>>>>>>compilers. I have 16,000 hours of development time in my current project.
>>>>>>There is a 100 line function that must take no longer than 1/10 second to
>>>>>>execute. I can just barely achieve this with MSVC++ 6.0. MSVC++ 7.0 has
>>>>>>had some of its optimizations disabled. I eventually will need to port
>>>>>>this to C# .NET. This is a case where hand tweaked assembly language would
>>>>>>be appropriate. I figured that hand tweaked CIL would be the .NET
>>>>>>equivalent of hand tweaked assembly language.
>>>>>>
>>>>>> "Nicholas Paldino [.NET/C# MVP]" <mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote
>>>>>> in message news:OCvd7unCGHA.2644@xxxxxxxxxxxxxxxxxxxxxxx
>>>>>>> Peter,
>>>>>>>
>>>>>>> You can write it, but you would have to create a module with IL, and
>>>>>>> then compile that into your assembly (or just write the whole assembly).
>>>>>>>
>>>>>>> Also, what optimizations do you think you can make? Ultimately, you
>>>>>>> suffer from the fact that Windows is not a real-time OS, and nothing you
>>>>>>> can do will change that. On top of that, the JIT is what's going to
>>>>>>> optimize your code again after you try to, so you might actually end up
>>>>>>> hurting yourself more than helping yourself.
>>>>>>>
>>>>>>> If you post the code you are trying to optimize, we can try and tell
>>>>>>> you where you might make some improvements, but dipping down to the IL
>>>>>>> level is most likely not going to help you much.
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> - Nicholas Paldino [.NET/C# MVP]
>>>>>>> - mvp@xxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>>>>>
>>>>>>>
>>>>>>> "Peter Olcott" <olcott@xxxxxxx> wrote in message
>>>>>>> news:7t%rf.37887$QW2.9998@xxxxxxxxxxxxx
>>>>>>>> Cab you write code directly in the Common Intermediate language? I need
>>>>>>>> to optimize a critical real-time function.
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>


.

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