[prev in list] [next in list] [prev in thread] [next in thread] 

List:       kde
Subject:    Re: KPager?
From:       Adolf Koenig <rzuw001 () rz ! uni-wuerzburg ! de>
Date:       1999-09-02 12:58:30
[Download RAW message or body]

> Why KPager periodically crashed with core dump? Or without, in
> /var/log/kernel appear message "out of swap space" when swap used at 28%
> > -) (swapinfo says so)
> 
 
 I cannot tell you, why your Kpager crashes, but to your question concerning
 swap space:

 Although that's not a genuine KDE-topic, I think that few readers of the list
 will be angry about an explanation. 
 
 AFAIK from other systems, and I think that LINUX will not significantly differ:
   
 How can the system be 'out of swap space' when actual usage of swap is much less
 than 100 %?
 
 When a process is started, and sometimes during it's running, it demands a certain
 amount of (virtual) RAM memory, depending of the program code and data size and \
other  parameters. When a process is interrupted, potentially all  physical
 memory pages have to be saved on disk, that is in swapspace. In order to avoid
 deadlock situations, the sytem has to keep track of the processes' memory \
requirements,  and to make sure that an interrupted process in  a n y  c a s e  will \
get the needed swap  memory to save all the physical memory, the available swapspace \
is reduced according   to the job's requirements when the process is started (or \
expanded).  That is: 
      available swapspace = total swap space - (sum of memory requirements of all
                                                                               \
                running and swapable processes)
       (some processes are too important to be swapped out and stay resident)         \
                
       If a process wants to start or expand and there is no more or not enough \
available   swapspace, the system the system is 'out of swap space'

  On the other side:
      swapspace is really used, that is, physical memory pages are really swapped
      out, only if the physical memory is not enough to satisfy the memory \
requirements  of a new or expanding or (interrupted and to be) continued process.
      
  Thus:
  1) if your physical memory is larger than the total swapspace, theoretically
  the seemingly contradictory situation is possible, that the system is out of
  swapspace without really using a single page of swap.                               \
  
  2) The total swap space should be at least as large as the physical memory.
  Otherwise it could be that part of the memory is never used and the system
  refuses start of processes because of 'out of swap space', although they
  would easily fit into the physical memory.
 
 Greetings
 
 Adolf  
-- 
Send posts to:  kde@lists.netcentral.net
 Send all commands to:  kde-request@lists.netcentral.net
  Put your command in the SUBJECT of the message:
   "subscribe", "unsubscribe", "set digest on", or "set digest off"
PLEASE READ THE ARCHIVED MESSAGES AT http://lists.kde.org/ BEFORE POSTING
**********************************************************************
This list is from your pals at NetCentral <http://www.netcentral.net/>


[prev in list] [next in list] [prev in thread] [next in thread]