Subject: file creation decreases memory !
To: None <>
From: None <>
List: tech-userlevel
Date: 03/02/2004 11:41:48

we are facing a problem in our system runinng netbsd.
we are trying to create a file on our file system (compact flash mounted
ffs and memory based file system for system image and NO SWAP mounted !) ..

we are observing that the file copied decreases the top shown free memory ?
and increases the File memory shown by top i.e
Memory: 50M Act, 72M Inact, 220K Wired, 1944K Exec, 110M File, 96M Free

The File and Free are proportinately increased and decreased by same amount

This goes on even if we issue sync command (wasnt it supposed to write back
these dirty pages back to disk ?)
io_flush kernel thread has also been seen running but doesnt changes these
top output. ..
the file in question being  say 38 MB .. and command is " cp file1 file 2"

Can some body explain why it is happening ..

My questions /:
what happens further is that if say a program asks for memory it goes down
saying out of swap ??
so why isnt the file system being written back to ??
Could declaration of no swap affecting the vnode handling by netbsd ??
we dont have swap declared / mounted is all I can see as a difference
between a server runinng netbsd where also repetitive file copies does
decreases memory free as reported by top but after a point the error shown
is file system full and not out of swap, as we are getting here ..
could we be giving something in kernel options which could have resulted
this ?
What is this File field anyways, how is it calculated and how is the free
field calculated, this seems to be different from linux ..

why isnt it saying file system full (which isnt) as df -k shows some life
left ..
Please point to some relavant direction.

- Rajan