Regarding Page Cache ,Buffer Cachein disabling in Linux Kernel.

Regarding Page Cache ,Buffer Cachein disabling in Linux Kernel.

[Anil Kumar]

Hello All,
  I am new to this mailing list.I am going through the linux kernel 
 source code. I want to disable the Page Caching,Buffer Caching  in
 the Kernel.How can i do it  ?
 Thanks in Advance.
Regards 
Anil


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Re: Regarding Page Cache ,Buffer Cachein disabling in Linux Kernel.

[Rik van Riel]

On Mon, 29 Jul 2002, Anil Kumar wrote:

>   I am new to this mailing list.I am going through the linux kernel
>  source code. I want to disable the Page Caching,Buffer Caching  in
>  the Kernel.How can i do it  ?

You cannot disable it, without the page cache read(2) and write(2)
don't have a target to read or write data to/from...

Rik
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Bravely reimplemented by the knights who say "NIH".

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Re: Regarding Page Cache ,Buffer Cachein disabling in Linux Kernel.

[Jonathan Morton]

>  a) i allow page caching then there is going to be 2 copies of
>   data in my system and i want to avoid it.

If you're using memory, the pages will be evicted from the cache.  It 
is NOT a problem.

-- 
--------------------------------------------------------------
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mail:     chromi@chromatix.demon.co.uk
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Re: Regarding Page Cache ,Buffer Cachein disabling in Linux Kernel.

[Anil Kumar]

Hello All,
  
> On Mon, 29 Jul 2002, Anil Kumar wrote:
> 
> >   I am new to this mailing list.I am going through the linux kernel
> >  source code. I want to disable the Page Caching,Buffer Caching  in
> >  the Kernel.How can i do it  ?
> 
> You cannot disable it, without the page cache read(2) and write(2)
> don't have a target to read or write data to/from...
> 
  On My board i have RAM of 8 MB and swapping is disabled.when my 
 system comes up i download binaries (Linux Kernel + Other Application
 Binaries) from flash on the board to the RAM and start processing.

  As i think if 

 a) i allow page caching then there is going to be 2 copies of
  data in my system and i want to avoid it.

 b) Always  my process pages are going to be in RAM and there would be
    no page fault(Unless application have bugs b'se swapping is 
    disabled).
  
   
Regards
Anil


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Re: Regarding Page Cache ,Buffer Cachein disabling in LinuxKernel.

[Anil Kumar Nanduri]

Hi Anil,
    I suggest you to read some documents on 2.4 linux memory management
    http://home.earthlink.net/~jknapka/linux-mm/pagecache.html
    then read code of 2.4.

    Actually in 2.4 both the swap cache and page cache are unified with
    the concept of struct address_space,
    I mean Any physical page will be in active list (or) inactive clean list
    (or) inactive dirty list.

    If that page is mmaped one (i mean if it is for a file) then it will also
be
    in the inode list of that file (no swap for this page).

    If that page was identified to be swapped(!mmaped || !text || etc..)
    out then it will also be in the swapper_space inode queue until it
    is reclaimed by the system.

    Please remember it is the same page which is on two queues( not two copies)

    In your case As you will not be having any swap...
    all the mmaped files(if you have mounted partition with r/rw),
    text region of executables  will still behave as if they have swap.

    but for other pages which actually need swap like data segments
    will not be in swapper_space inode queue as the get_swap_page()
    function will fail to return an valid entry.

    Now tell me why do you want to disable page cache/ swap cache?

    May be i will suggest you one thing that might be of use to you is
    to have a compressed memory based swap
    ( I am thinking of implementing).

Please let me know if i am not clear enough.

Thanks,
-anil.


Jonathan Morton wrote:

> >  a) i allow page caching then there is going to be 2 copies of
> >   data in my system and i want to avoid it.
>
> If you're using memory, the pages will be evicted from the cache.  It
> is NOT a problem.
>
> --
> --------------------------------------------------------------
> from:     Jonathan "Chromatix" Morton
> mail:     chromi@chromatix.demon.co.uk
> website:  http://www.chromatix.uklinux.net/
> geekcode: GCS$/E dpu(!) s:- a21 C+++ UL++ P L+++ E W+ N- o? K? w--- O-- M++$
>            V? PS PE- Y+ PGP++ t- 5- X- R !tv b++ DI+++ D G e+ h+ r++ y+(*)
> tagline:  The key to knowledge is not to rely on people to teach you it.
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/

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