Zero copy between ISR, kernel and User

Zero copy between ISR, kernel and User

[Wink Saville]

Hello,

I would like to allow the transferring of data between ISR's, kernel and 
user code, without requiring copying. I envision allocating buffers in 
the kernel and then mapping them so that they appear at the same 
addresses to all code, and never being swapped out of memory.

Is this feasible for all supported Linux architectures and is there 
existing code that someone could point me towards?

Regards,

Wink Saville

Re: Zero copy between ISR, kernel and User

[Stephen Hemminger]

On Tue, 26 Sep 2006 21:01:45 -0700
Wink Saville <wink@saville.com> wrote:

> Hello,
> 
> I would like to allow the transferring of data between ISR's, kernel and 
> user code, without requiring copying. I envision allocating buffers in 
> the kernel and then mapping them so that they appear at the same 
> addresses to all code, and never being swapped out of memory.
> 
> Is this feasible for all supported Linux architectures and is there 
> existing code that someone could point me towards?
> 
> Regards,
> 
> Wink Saville
> 

Your better off having application mmap a device, then transfer
the data to there. Something like AF_PACKET.

-- 
Stephen Hemminger <shemminger@osdl.org>

Re: Zero copy between ISR, kernel and User

[Wink Saville]

Stephen Hemminger wrote:
> On Tue, 26 Sep 2006 21:01:45 -0700
> Wink Saville <wink@saville.com> wrote:
>
>   
>> Hello,
>>
>> I would like to allow the transferring of data between ISR's, kernel and 
>> user code, without requiring copying. I envision allocating buffers in 
>> the kernel and then mapping them so that they appear at the same 
>> addresses to all code, and never being swapped out of memory.
>>
>> Is this feasible for all supported Linux architectures and is there 
>> existing code that someone could point me towards?
>>
>> Regards,
>>
>> Wink Saville
>>
>>     
>
> Your better off having application mmap a device, then transfer
> the data to there. Something like AF_PACKET.
>
>   
Is there some reason a kernel module can't mmap first, for instance I 
assume display drivers might do that? One of the reasons I need it to 
done in the kernel first is that data could come from the device or 
other entities before the application is running.

But I will study AF_PACKET handling.

Thanks,

Wink