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Bug 214038 - Kernel starts swapping when 148780k free/3054716k cached
Kernel starts swapping when 148780k free/3054716k cached
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
i686 Linux
medium Severity medium
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Assigned To: Kernel Maintainer List
Brian Brock
Depends On:
  Show dependency treegraph
Reported: 2006-11-04 17:44 EST by Robert Scheck
Modified: 2008-06-04 15:22 EDT (History)
2 users (show)

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2008-06-04 15:22:07 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Robert Scheck 2006-11-04 17:44:53 EST
Description of problem:
IMHO the following kernel behaviour is broken:

$ free
             total       used       free     shared    buffers     cached
Mem:       3960936    3812156     148780          0     195840    3054716
-/+ buffers/cache:     561600    3399336
Swap:      1048552         64    1048488

Why the hell does the kernel start swapping when 148780k free and 3054716k 
cached? Okay, currently only 64k are swapped but this is unnecessary when 
148780k are free, isn't it?

Version-Release number of selected component (if applicable):

How reproducible:
Put 4 GB of RAM into a server and rebuild gcc, no swapping. Let the box run it's 
normal services (httpd, vsftpd, sshd etc.) with low use (< 0.25 load) after it - 
without rebooting the box between - and see what I posted above.

Actual results:
Kernel starts swapping when 148780k free/3054716k cached

Expected results:
Swapping first when RAM is completely used...
Comment 1 Bug Zapper 2008-04-03 14:35:39 EDT
Based on the date this bug was created, it appears to have been reported
against rawhide during the development of a Fedora release that is no
longer maintained. In order to refocus our efforts as a project we are
flagging all of the open bugs for releases which are no longer
maintained. If this bug remains in NEEDINFO thirty (30) days from now,
we will automatically close it.

If you can reproduce this bug in a maintained Fedora version (7, 8, or
rawhide), please change this bug to the respective version and change
the status to ASSIGNED. (If you're unable to change the bug's version
or status, add a comment to the bug and someone will change it for you.)

Thanks for your help, and we apologize again that we haven't handled
these issues to this point.

The process we're following is outlined here:

We will be following the process here:
http://fedoraproject.org/wiki/BugZappers/HouseKeeping to ensure this
doesn't happen again.
Comment 2 Robert Scheck 2008-04-03 16:46:03 EDT
Hum? Since when is Rawhide no longer maintained? The problem still exists in 
Comment 3 Bug Zapper 2008-05-13 22:27:12 EDT
Changing version to '9' as part of upcoming Fedora 9 GA.
More information and reason for this action is here:
Comment 4 Dave Jones 2008-06-04 15:22:07 EDT
I believe what you're seeing is the effect of the swap cache. Where something
was swapped out briefly (whilst there was memory pressure), and we keep
references to the swapped out version on disk just in case the situation
reoccurs, so that we don't have to write it out to swap a second time, we just
throw out the in-memory references.

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