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RE: Red Hat memory allocation




Hi Marco , David, 

> Is the 'page cache' indeed the cache used for page I/O?

Isnt it page cache is used for caching disk io , (data that is read from
disk is stored in the page cache to minimize the amount of disk I/O .)

> Is the 'buffer cache' indeed the cache used for disk I/O?

And isnt it used only for inode caching?

Regards,
Tolga Evren

-----Original Message-----
From: redhat-list-bounces redhat com
[mailto:redhat-list-bounces redhat com] On Behalf Of David Tonhofer,
m-plify S.A.
Sent: Thursday, October 13, 2005 10:39 PM
To: Shaw, Marco
Cc: General Red Hat Linux discussion list
Subject: RE: Red Hat memory allocation

(Cc-ed to list in case anyone is interested)

--On Thursday, October 13, 2005 4:08 PM -0300 "Shaw, Marco"
<Marco Shaw aliant ca> wrote:

> If I may, how did you get that tree view of the state of memory?
>
> By hand?  From knowledge & experience?
>
> Thanks,
> Marco


Err... yes. Basically "by hand". It's a perl program I did while
trying to understand the output of free(1) and the values
found in /proc (I used the O'Reilly book on /proc and the one on the
Kernel).

Some things I never got sorted out completely. Sounds like cosmology:

> Why is "sum(RSS)" != "Mapped memory" ?
> Why is "floating" (a correction) not exactly 0 (it used to be under
2.2
  kernel I think)
> Are 'slab' and 'page tables' correctly grouped under 'allocated'?
> Is the 'page cache' indeed the cache used for page I/O?
> Is the 'buffer cache' indeed the cache used for disk I/O?

As I'm not exactly 100% sysop, I gave up once I had satisficing results.

It's nothing complicated anyway - here it is:

<http://misato.m-plify.net/parse_free.pl>

Best regards,

-- David





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