mmap operation

mmap operation

[Gilles Pokam]

Hi,

I have implemented a module for buffer management in the 2.0.34 linux kernel.
Now i'm using the write and read method for transfering data between the kernel
and user space. I have noticed that the overhead of these 2 operations are 
quite big, because each time a system call is invoked. So i decided to improve 
my module by implementing the mmap operation. The mmap operation works well
when mapping only one page size. But above this size, for example with an order
of at least 1, the later operation fails to work! I have noticed that above
4096 (one page) bytes the zero page is mapped instead! 
Could someone help mee solve this problem ? (i use the nopage operation in my
mmap method and cluster of 16 pages).

Thanks.
       Gilles 
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Re: mmap operation

[Stephen C. Tweedie]

Hi,

On Mon, 10 May 1999 18:02:10 +0200 (MET DST), Gilles Pokam
<pokam@cs.tu-berlin.de> said:

> I have implemented a module for buffer management in the 2.0.34 linux
> kernel.  Now i'm using the write and read method for transfering data
> between the kernel and user space. I have noticed that the overhead of
> these 2 operations are quite big, because each time a system call is
> invoked. So i decided to improve my module by implementing the mmap
> operation. The mmap operation works well when mapping only one page
> size. But above this size, for example with an order of at least 1,
> the later operation fails to work! I have noticed that above 4096 (one
> page) bytes the zero page is mapped instead!  Could someone help mee
> solve this problem ? (i use the nopage operation in my mmap method and
> cluster of 16 pages).

The entire VM works by mapping single pages.  It would be a large task
to change this.

--Stephen
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