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тАО02-13-2009 05:57 AM
тАО02-13-2009 05:57 AM
Linux kernel free mem usage clarification
Red Hat Enterprise Linux AS release 3 (Taroon Update 9)
Linux hostname 2.4.21-53.ELsmp #1 SMP Wed Nov 14 03:54:12 EST 2007 i686 i686 i386 GNU/Linux
# free -mt
total used free shared buffers cached
Mem: 10024 10004 19 0 61 8540
-/+ buffers/cache: 1401 8622
Swap: 4095 218 3877
Total: 14120 10223 3897
getting following messages while doing "service nfd start". nfsd is failed to start.
Feb 12 17:14:56 shdbl2p nfs: Starting NFS services: succeeded
Feb 12 17:14:56 shdbl2p nfs: rpc.rquotad startup succeeded
Feb 12 17:14:56 shdbl2p nfsd[16431]: nfssvc: Cannot allocate memory
Feb 12 17:14:56 shdbl2p nfs: rpc.nfsd startup failed
Feb 12 17:14:56 shdbl2p nfs: rpc.mountd startup succeeded
This memory error looks contradictory my understanding on the LINUX free memmory (MEM free=free+ cached)calculation. As of now i hav 8GB under cached.
Could some one explain? OR is understaning wrong free mem?
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тАО02-13-2009 06:19 AM
тАО02-13-2009 06:19 AM
Re: Linux kernel free mem usage clarification
Maybe, some kernel parameter or shell limit is in place.
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тАО02-13-2009 06:29 AM
тАО02-13-2009 06:29 AM
Re: Linux kernel free mem usage clarification
nfslock service may not be running. That could cause this problem.
You have sufficient memory.
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тАО02-13-2009 06:59 AM
тАО02-13-2009 06:59 AM
Re: Linux kernel free mem usage clarification
- the design limit of 32-bit Linux memory management: the standard maximum userspace size without any highmem workarounds is "1 GB minus all memory-mapped hardware (like VideoRAM of the display adapter)".
- a 32-bit processor simply cannot directly access more than 4 GB: it does not have enough bits on its address bus for that. A workaround is PAE, which is essentially a form of bank-switching.
The side effect of the combination of these workarounds is that all memory is not equal. The first 1 GB or so of the memory is considered "low" memory. The rest is "high" memory. For some purposes (like I/O buffers), high memory is not usable: low memory must be used.
(For example, to transfer data from one segment of high memory to another, the system may need to copy it from the source location to low memory, then switch high memory banks and copy the data from low memory to the target segment.)
It is possible to run out of low memory while still having plenty of high memory. I have a suspicion this is happening in your case.
Please run:
egrep 'High|Low' /proc/meminfo
to see your high/low memory situation.
If your workload demands more than 1 GB of low memory, I'm afraid the only solution is to upgrade to a 64-bit version of the OS.
For quite a while, I've been following this policy: if a new server is installed with more than 2 GB of memory or it seems likely that its memory will be expanded beyond that limit in the foreseeable future, I'd strongly recommend installing a 64-bit version of the OS from the beginning.
MK
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тАО02-13-2009 07:53 AM
тАО02-13-2009 07:53 AM
Re: Linux kernel free mem usage clarification
# egrep 'High|Low' /proc/meminfo
HighTotal: 9567024 kB
HighFree: 18976 kB
LowTotal: 697836 kB
LowFree: 22064 kB
How can i check the cpu is 32bit?Just curious. I know my linux kernel is 32bit
Does nfsd uses high or low memory? In my case free is low on both cases.
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тАО02-13-2009 10:12 AM
тАО02-13-2009 10:12 AM
Re: Linux kernel free mem usage clarification
http://kerneltrap.org/node/2450
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тАО02-16-2009 01:27 AM
тАО02-16-2009 01:27 AM
Re: Linux kernel free mem usage clarification
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тАО02-17-2009 11:16 PM
тАО02-17-2009 11:16 PM
Re: Linux kernel free mem usage clarification
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тАО02-18-2009 01:56 AM
тАО02-18-2009 01:56 AM
Re: Linux kernel free mem usage clarification
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тАО02-18-2009 07:00 AM
тАО02-18-2009 07:00 AM
Re: Linux kernel free mem usage clarification
Linux hostname 2.4.21-53.ELsmp #1 SMP