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List:       linux-arm-kernel
Subject:    Re: perfomance of copy_to/from_user
From:       Thomas =?iso-8859-1?q?W=F6ckinger?= <twc () sbox ! tugraz ! at>
Date:       2004-10-06 16:54:58
Message-ID: 200410061854.58801.twc () sbox ! tugraz ! at
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On Wednesday 06 October 2004 18:28, you wrote:
> On Wed, 6 Oct 2004, 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?
>
> Hardly.
>
> > 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.
>
> It is possible for you to mmap() the 256k kernel buffer into user space
> and avoid copying the data entirely.

sometimes i have to transfer about 1MB (imagedata) beetween the dsp card and 
the xscale, and it's hard to get such a big continous buffer, especially when 
i have four dsp card's and each of them want to transfer such an datachunk to 
the host

>
>
> Nicolas

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