Bug 53224 - memory stays in
memory stays in
Product: Red Hat Linux
Classification: Retired
Component: kernel (Show other bugs)
i686 Linux
medium Severity high
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Assigned To: Arjan van de Ven
Brock Organ
Depends On:
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Reported: 2001-09-05 03:32 EDT by Mike
Modified: 2008-08-01 12:22 EDT (History)
0 users

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Last Closed: 2004-09-30 11:39:10 EDT
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Description Mike 2001-09-05 03:32:54 EDT
From Bugzilla Helper:
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)

Description of problem:
the system runs mysql database and tomcat. when ONLY system starts it uses 
60 MB of 1GB RAM. after we start mysql and tomcat, the system uses 
200MB.when we shutdown mysql & tomcat it still shows 200MB as used.

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

How reproducible:

Steps to Reproduce:
1.it happens with default & new-recompiled kernel 2.4.2
2.start some memory eat processes
3.make sure it uses enough memory
4.shutdown the processes
5. make sure in top that it shows same amoung of memory as "used" 
6. reboot helps

Actual Results:  the system does not free memory. 

Expected Results:  the system started with 60MB, after running our 
processes it used 400MB,after closing our processes the system should 
unused memory.

Additional info:

i tried to put a new kernel 2.4.9 but have the same problem.
Comment 1 Arjan van de Ven 2001-09-05 03:43:33 EDT
I'm fairly convinced one of the kernel caches (such as the disk-cache) that
retains the memory in case you use it again. You can force these caches to be
cleared by typing

"dd if=/dev/zero of=/tmp/foofile bs=1M count=1024 ; rm /tmp/foofile"

if this "clears" the memoryleak you see it's the diskcache; this memory will be
freed on demand.
Comment 2 Mike 2001-09-05 03:58:49 EDT
the problem happens on RAM , not with disk space/cache.
There was a same problem with 2.2 kernel and there was a patch to make kernel 
free unused memory.
Comment 3 Arjan van de Ven 2001-09-05 04:01:56 EDT
The diskcache is in RAM. And you WANT the kernel to keep that around until you
really need the memory, as your next access to the same data on disk will be
very fast due to the cache.

The kernel will just free the memory used for caches when applications need it.
The "dd" line I gave will need memory and as a result the caches will get freed.
Comment 4 Mike 2001-09-05 04:08:41 EDT
when i start our processes again (mysql, tomcat with many java processes, 
oracle) - they are all fail with error "not enough memory". The reboot fixes it 
well and they all can be started. Even more, when i start only one of them 
(mysql) - i got the same error. maybe there is a way to signal to the kernel to 
not keep caches and clear them when process end?
please suggest.
Comment 5 Arjan van de Ven 2001-09-05 07:18:50 EDT
hmm. this sounds like programs are not releasing their shared memory.
Could you run the "ipcs" program to see if there is a lot of shared memory left
in use after the programs have existed ?
Comment 6 Mike 2001-09-05 08:50:36 EDT
OK. here is a log. The system was up and running. all our processes were up too 
(mysql, tomcat, oracle). There were 300MB of RAM used. now all process are 
down. the system shows that it still uses 300MB. the output of "ipcs" before 
processes shutdown and after is attached.

------ Shared Memory Segments --------
key       shmid     owner     perms     bytes     nattch    status      
0x00280267 0         root      644       1048576   3                     
0x00000000 32769     oracle    640       77824     14                    
0x00000000 65538     oracle    640       17825792  14                    
0x00000000 98307     oracle    640       17825792  14                    
0x00000000 131076    oracle    640       20971520  14                    
0x847fad80 163845    oracle    640       16961536  14                    

------ Semaphore Arrays --------
key       semid     owner     perms     nsems     status      
0x00280269 0         root      666       14        
0x8bedf710 131073    oracle    640       154       

------ Message Queues --------
key       msqid     owner     perms     used-bytes  messages    

------ Shared Memory Segments --------
key       shmid     owner     perms     bytes     nattch    status      
0x00280267 0         root      644       1048576   4                     

------ Semaphore Arrays --------
key       semid     owner     perms     nsems     status      
0x00280269 0         root      666       14        

------ Message Queues --------
key       msqid     owner     perms     used-bytes  messages    

please suggest
Comment 7 Bugzilla owner 2004-09-30 11:39:10 EDT
Thanks for the bug report. However, Red Hat no longer maintains this version of
the product. Please upgrade to the latest version and open a new bug if the problem

The Fedora Legacy project (http://fedoralegacy.org/) maintains some older releases, 
and if you believe this bug is interesting to them, please report the problem in
the bug tracker at: http://bugzilla.fedora.us/

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