On 02/09/2011 06:13 PM, john wrote:
> I'll also add that after all users log out memory usage remains high.
> Once users have logged off and processes have ended, I would expect
> memory to be freed.

Cache, which is what the bulk of your memory is used for, is not
directly related to running processes so in general I would not expect
to see much memory freed when everyone logs out.

Don't worry about it though.  Having memory used for cache is a good
thing.  It puts otherwise wasted free memory to use speeding up your system.

>> Thanks for the good news. However, the the additional bit that I
>> should have mentioned is that once the memory usage shows
>> that I am nearly "out" of ram , TOP shows that the disk will start
>> using SWAP. I thought that what should happen is that as memory
>> demands grow the CPU
>>  should move stale data from buffers to disk and free more memory for
>> applications and that swapping was a sign that it was digging into the
>> disk for VM.
>>  Am I just not understanding how this all works?

I suspect you are not understanding how this all works, but then kernel
memory management is not a simple thing.  Suffice it to say the kernel
it is probably doing the right thing.  If it is using a moderate amount
of swap it is probably because the kernel decided the system would be
better off removing some rarely used code from RAM instead of removing
cache.  If you want some control over how readily stuff is swapped out
you can google swappiness.

However, like I said above, cache is a good thing and in general you
should not be trying to prevent your system from using it.  Think of
cache as a dynamic SSD but much faster.  Who wouldn't want that?

Jeff

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