Used Memory Not Clearing Down On Redhat Machines.

[Tolga Evren]

Hi ,

Look at my memifo pls:

        total:    used:    free:  shared: buffers:  cached:
Mem:  8490827776 8118534144 372293632        0 252133376 4320608256
Swap: 25165725696 113704960 25052020736
MemTotal:      8291824 kB
MemFree:        363568 kB
MemShared:           0 kB
Buffers:        246224 kB
Cached:        4215008 kB
SwapCached:       4336 kB
Active:        2952512 kB
Inact_dirty:   2277600 kB
Inact_clean:    211712 kB
Inact_target:  1088352 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:      8291824 kB
LowFree:        363568 kB
SwapTotal:    24575904 kB
SwapFree:     24464864 kB
Committed_AS: 621197056 kB
HugePages_Total:     0
HugePages_Free:      0
Hugepagesize:    262144 kB


The inact_dirty is 2277600 kB .  

> http://www.redhat.com/magazine/001nov04/features/vm/
> Pages in the inactive dirty state ought to be getting flushed 
> out to disk, but it looks like this isn't happening.
> 
> I'm no kernel expert, but it seems to me that something is 
> causing the kernel not to properly launder the inactive dirty 
> memory.  This could be a kernel bug, so if you are sure you 
> don't have any hung processes that could be holding the 
> memory open, you should check to see if there is a newer 
> kernel available for your system.


How can i be sure that this is a bug?

Kind Regards,
Tolga Evren




-----Original Message-----
From: redhat-list-bounces at redhat.com
[mailto:redhat-list-bounces at redhat.com] On Behalf Of Smith, Albert
Sent: Thursday, September 15, 2005 8:35 PM
To: General Red Hat Linux discussion list
Subject: RE: Used Memory Not Clearing Down On Redhat Machines.

> -----Original Message-----
> From: redhat-list-bounces at redhat.com 
> [mailto:redhat-list-bounces at redhat.com] On Behalf Of Eris Caffee
> Sent: Friday, August 12, 2005 11:17 AM
> To: General Red Hat Linux discussion list
> Subject: Re: Used Memory Not Clearing Down On Redhat Machines.
> 
> > 15:20:33  up 14 days,  2:16,  1 user,  load average: 0.00, 
> 0.00, 0.00
> > 49 processes: 48 sleeping, 1 running, 0 zombie, 0 stopped
> > CPU states:  cpu    user    nice  system    irq  softirq  
> iowait    idle
> >            total    0.8%    0.0%    0.2%   0.0%     0.6%    
> 0.0%  198.4%
> >            cpu00    0.0%    0.0%    0.0%   0.0%     0.0%    
> 0.0%  100.0%
> >            cpu01    0.8%    0.0%    0.2%   0.0%     0.6%    
> 0.0%   98.4%
> > Mem:  3599032k av, 2926964k used,  672068k free,       0k 
> shrd,   82052k
> > buff
> >                     469844k actv, 1731916k in_d,   54940k in_c
> > Swap: 2044072k av,       0k used, 2044072k free             
>     2614264k
> > cached
> 
> You have an awful lot of memory in the in_d state.  That is 
> "Inactive Dirty".  There's a description of it and the other 
> memory states (for 2.4 kernels at least) here:
> http://www.redhat.com/magazine/001nov04/features/vm/
> Pages in the inactive dirty state ought to be getting flushed 
> out to disk, but it looks like this isn't happening.
> 
> I'm no kernel expert, but it seems to me that something is 
> causing the kernel not to properly launder the inactive dirty 
> memory.  This could be a kernel bug, so if you are sure you 
> don't have any hung processes that could be holding the 
> memory open, you should check to see if there is a newer 
> kernel available for your system.
> 
> Of course, you should also double check to make sure there 
> really isn't some process from the analysis job still running 
> and holding all of this memory open.
> 
> Eris Caffee
> 
> 
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> 
> 

I did some investigation with RH EL4 and it looks like this memory
problem is addressed with 2.6.x line of kernel. I am currently compiling
2.6.13 manually on my EL3 to see the results.

I will keep you posted.

Albert Smith
Sr. Unix Systems Administrator
HPCSA, RHCT  
Genex Services
440 E. Swedesford Rd.
Wayne, PA 19087
albert.smith at genexservices.com
(610) 964-5154



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