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amit shukla 10-09-2009 05:47 AM

kernel 2.6.9-89.0.9.ELsmp related question
We are currently on the kernel version 2.6.9-89.0.9.ELsmp and we have seen cases of cache usage going very high.(almost till the level of total available memory)
To solve this issue we used the following command:

echo 3 > /proc/sys/vm/drop_caches

The result is that it drops clean caches, dentries and inodes from memory, causing that memory to become free.

The man pages on the proc displays that drop_caches is available since the kernel version 2.6.16.
refert to the url below :

However as stated earlier drop_caches works on kernel version 2.6.9-89.0.9.ELsmp as well.
How can it be confirmed if its a safe option to use drop_caches in 2.6.9-89.0.9.ELsmp or
is any other source from where this can be verified ?

Thanks in advance.

cardy 10-09-2009 05:59 AM

I would question as to why this is a problem. generally Linux will utilise free memory for caching (and other tasks) to help improve performance and responsiveness. Should an application need the memory held by the cache the kernel will release it as required.

What in your setup requires that the memory be left unused (ie. free) rather than being utilised for caching to help with overall system performance ?

AlucardZero 10-09-2009 09:00 AM

This is not a problem.

RHEL kernels may have the old numbers but they are closer to the newer kernels, really.

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