Summary: Idle process taking up 500 megs of memory.

From: Leo Schmidt <leo_at_NIC.MSUS.EDU>
Date: Mon, 30 Mar 1998 14:23:17 -0600 (CST)

Thanks to everyone who responded.


The Question was:

> Problem:
>
> doing a 'ps -auxww' and grepping for 'idle', I get:
>
>
> USER PID %CPU %MEM VSZ RSS TTY S COMMAND
> root 0 0.0 4.0 524M 20M ?? R < [kernel idle]
>
> The man page for "ps" states that "VSZ" is "Process virtual address
> size". So is that really 524 Meg that it has allocated? The %mem is
> listed as 4.0, but 4% of 1 gig (real+swap) is close to 40 megs, not
> 524 megs.
>
>
> Hardware/OS specs:
> We have an AlphaServer 2100 4/275 with one processor,
> 512MB RAM, 512MB swap (deferred mode swapping).
>
> We're running on DU 4.0B.
>
> `uname -a` says:
> OSF1 bigtest.mankato.msus.edu V4.0 564 alpha


Short answers:

1) The "RSS" value is the one which is most closely related to the
actual size of the process.

2) The percentage listed under "%MEM" is percentage of real memory (as
opposed to swap space) used. So 4% of 512MB (real memory) is 20M --
which correlates with the RSS value.



The replies I received are listed below, minus many mail headers and
copies of my original post.

--------------------
>From alan_at_nabeth.cxo.dec.com Tue Mar 24 15:02:43 1998
Return-Path: <alan_at_nabeth.cxo.dec.com>
Subject: Re: Idle process taking up 500 megs of memory?
Date: Tue, 24 Mar 98 14:02:56 -0700


        That's the kernel idle thread. It can be safely ignored
        and shouldn't be touched. The virtual address size may
        be the only good clue in the whole system how much total
        virtual memory is being used though.

----------
>From deniel_at_worldnet.fr Tue Mar 24 16:11:50 1998
Return-Path: <deniel_at_worldnet.fr>
Date: Tue, 24 Mar 1998 23:17:11 +0100
Subject: Re: Idle process taking up 500 megs of memory?

...

The RSS (Resident Set) is the amount of memory that is resident
(not swapped) and the %mem is related to the virtual memory (512MB)
(4% of 512 is close to 20M).

--
Laurent DENIEL            | E-mail: deniel_at_worldnet.fr
Paris, FRANCE             |         deniel_at_fr.airsysatm.thomson-csf.com
                          | WWW   : http://www.worldnet.fr/~deniel
    All above opinions are personal, unless stated otherwise.
----------
>From tpb_at_zk3.dec.com  Tue Mar 24 16:56:04 1998
Return-Path: <tpb_at_zk3.dec.com>
Subject: Re: Idle process taking up 500 megs of memory? 
Date: Tue, 24 Mar 98 17:55:57 -0500
From: "Dr. Tom Blinn, 603-884-0646" <tpb_at_zk3.dec.com>
The ps command doesn't have a good number to display for the kernel idle
PID.  If you really need to understand what's going on, I probably can dig
through the data structures that ps is examining, figure out why it has a
bogus value, and help you understand, but suffice it to say that for that
particular PID, the number is meaningless.
Tom
 
 Dr. Thomas P. Blinn, UNIX Software Group, Digital Equipment Corporation
  110 Spit Brook Road, MS ZKO3-2/U20   Nashua, New Hampshire 03062-2698
   Technology Partnership Engineering           Phone:  (603) 884-0646
    Internet: tpb_at_zk3.dec.com           Digital's Easynet: alpha::tpb
     ACM Member: tpblinn_at_acm.org         PC_at_Home: tom_at_felines.mv.net
  Worry kills more people than work because more people worry than work.
      Keep your stick on the ice.        -- Steve Smith ("Red Green")
     My favorite palindrome is: Satan, oscillate my metallic sonatas.
                                         -- Phil Agre, pagre_at_ucsd.edu
     Yesterday it worked / Today it is not working / UNIX is like that 
			-- apologies to Margaret Segall 
  Opinions expressed herein are my own, and do not necessarily represent
  those of my employer or anyone else, living or dead, real or imagined.
 
----------
>From xuzm_at_ns.cetin.net.cn  Tue Mar 24 21:36:46 1998
Return-Path: <xuzm_at_ns.cetin.net.cn>
Date: Wed, 25 Mar 1998 11:34:38 +0800
Subject: Re: Idle process taking up 500 megs of memory?
    hello!
    "VSZ" means  "Process virtual address size"  .You should check "RSS"
that
means " Real memory (resident set) size of the process (in 1024 byte
units)".
you can enter the following command:
ps -e -o rssize -o vsize -o pmem -o command|grep idle.
    Good Luck!
----Xu Zhimin
    xuzm_at_ns.cetin.net.cn
----------
>From PGIRISH_at_binariang.maxisnet.com.my  Tue Mar 24 22:19:43 1998
Return-Path: <PGIRISH_at_binariang.maxisnet.com.my>
Date: Wed, 25 Mar 1998 13:19:15 +0800
From: Girish Phadke <PGIRISH_at_binariang.maxisnet.com.my>
Subject: Re: Idle process taking up 500 megs of memory?
Hi
Appears to be confusion as if you give the command ps auxwww
it will show in following order.
USER       PID %CPU %MEM   VSZ  RSS TTY      S    STARTED         TIME COMMAND.
So  per your  output 
1) VSZ will be 524MB  i.e is virtaul pages
2) RSS i.e resident pages in real memory will be 20M 
3) %MEM shows how much real memory is used i.e 4% .So your total real memory is around 512MB
4) LAstly kernal idle is the name of process and the process is not idle  as seen by the status R i.e it is in runnable que.
regards 
----------
>From PGIRISH_at_binariang.maxisnet.com.my  Wed Mar 25 00:51:26 1998
Return-Path: <PGIRISH_at_binariang.maxisnet.com.my>
Date: Wed, 25 Mar 1998 15:49:51 +0800
From: Girish Phadke <PGIRISH_at_binariang.maxisnet.com.my>
Subject: I:U: kernal memory  usage can be seen by  vmstat -M command
hello 
one more update : or you can say one more mail to read  because as such you will get too many mail on the subject.
If you are worried why kernal is mapping so much memory give command vmstat -M 
You can reduce kernal memory use  by reducing n number of parameters to minimum requirement.Though it is not worth it as kernal memory will really grow  dependent on your free memory availablity. 
sorry again to bother you with one more mail.
regards
 
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>From peter_at_wiscpa.weizmann.ac.il  Wed Mar 25 06:34:52 1998
Return-Path: <peter_at_wiscpa.weizmann.ac.il>
From: Peter Stern <peter_at_wiscpa.weizmann.ac.il>
Subject: Re: Idle process taking up 500 megs of memory?
Date: Wed, 25 Mar 1998 15:34:36 +0300 (IDT)
%MEM refers to RSS and 20M/500M is 4.0%.
Best wishes,
Peter Stern
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Received on Mon Mar 30 1998 - 22:24:25 NZST

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