where did all my memory go? (file system cache)

[Julian Elischer]

slightly off topic but..

Brooks Davis wrote:

>On Wed, Feb 16, 2005 at 01:13:13PM -0800, Sean McNeil wrote:
>  
>
>The concept that most of your memory should be entierly free when the
>system is not under load is simply wrong.  The simplistic world view of
>memory being allocated to a specific task or entierly free simply isn't
>correct for all that it makes for nice graphs anyone can pretend they
>understand.  You can produce some sort of aproximation of the output you
>see on other systems by modifying the program to include inactive memory
>in free memory.  That's what I did with Ganglia.
>

what I really want is a way to FORce certain pages out of cache.
In particular I need to verify teh correctness of the version on 2ndary 
storage..

what I want is:

int fd = open("myfile",...);
write1GBfiletodisk(fd, data);
ioctl(fd, PURGEFROMCACHE);
perform_md5(fd);

and be sure that teh MD5 is that of what is on the disk.
not what is in RAM.

>
>-- Brooks
>
>  
>