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List:       linux-arm-kernel
Subject:    Re: perfomance of copy_to/from_user
From:       Stefano Coluccini <s.coluccini () caen ! it>
Date:       2004-10-06 16:21:29
Message-ID: 41641B89.7040805 () caen ! it
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Hi Thomas,
   I don't know if they are also in 2.6 kernels but in 2.4 you can write 
directly in user space buffers from kernel using the kiobuf technique.

I hope this can help you.

Bye,
Stefano.

Thomas Wöckinger wrote:
> Hi!
> 
> I have some performance Problems using copy_to_user or copy_from_user. I can 
> only transfer about 22,5 MB/s from or to userspace
> 
> I am using an Intel Xscale processor running on 500MHz pluged into idxp425 
> development board. An DSP card (pluged into PCI slot) is writing directly 
> into a 256K kernel space buffer.
> 
> the kernel version is 2.6.8.1
> 
> My first question is: can i speed up the copy_to/from_user?
> 
> if not, is it possible on an idxp425 board to access the whole memory 
> directly, so that i can write to the userspace buffer without using the 
> xscale.
> 
> i heard about dma_bounce buffer, but i am not sure if they are a solution form 
> my problem.
> 
> thx Tom
> 
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