Question about free/used memory on Linux

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From: Ravinandan Arakali (rarakali)
Date: Sunday, October 21, 2007 - 10:54 am

Hi kernel gurus,
I am trying to find out the memory that's used on my linux box.
I find that there are quite a few confusing metrics. How do
I find out the "true" used memory ?

1. For eg. "free -m" shows free memory (excluding buffers/caches) 
as 308 MB while I can see(from "df" output) that the the tmpfs 
partitions take up about 400 MB. So, does "free -m" not consider 
the tmpfs partitions ?

2. I try to add up RSS field of all processes reported by
"ps aux" command. But is it true that this would be misleading
in that, shared memory used by, say 2 processes would show
up twice here although there's only one copy in memory. Also
does this consider the fact that there's only one copy
of shared libraries ?

3. I guess "free -m" and "top" commands use /proc/meminfo 
and hence all these outputs are same ?

Thanks,
Ravi
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Messages in current thread:
Question about free/used memory on Linux, Ravinandan Arakali ( ..., (Sun Oct 21, 10:54 am)
Re: Question about free/used memory on Linux, Vaidyanathan Srinivasan, (Sun Oct 21, 12:00 pm)
RE: Question about free/used memory on Linux, Ravinandan Arakali ( ..., (Sun Oct 21, 1:21 pm)
Re: Question about free/used memory on Linux, Vaidyanathan Srinivasan, (Sun Oct 21, 10:50 pm)
RE: Question about free/used memory on Linux, Ravinandan Arakali ( ..., (Sun Oct 21, 11:28 pm)
Re: Question about free/used memory on Linux, Pádraig Brady, (Mon Oct 22, 3:05 am)
Re: Question about free/used memory on Linux, Helge Hafting, (Mon Oct 22, 4:51 am)
RE: Question about free/used memory on Linux, linux-os (Dick Johnson), (Mon Oct 22, 10:34 am)
RE: Question about free/used memory on Linux, Ravinandan Arakali ( ..., (Mon Oct 22, 6:58 pm)
RE: Question about free/used memory on Linux, Ravinandan Arakali ( ..., (Tue Nov 13, 11:14 pm)
Re: Question about free/used memory on Linux, Pádraig Brady, (Wed Nov 14, 4:58 am)
RE: Question about free/used memory on Linux, Ravinandan Arakali ( ..., (Wed Nov 14, 11:18 am)