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тАО04-07-2011 11:35 AM
тАО04-07-2011 11:35 AM
dev 10240 5 10235 0% 0 - 1 /dev/vg00/lvol2
reserve - 8335 -8335
memory 7790 3136 4654 40%
total 18030 11476 6554 64% - 0 -
My question is why the memory usage is only at 40% and yet the swap is already used for 5MB? Something wrong here? What is your recommendation?
Solved! Go to Solution.
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тАО04-07-2011 11:40 AM
тАО04-07-2011 11:40 AM
Re: RAM is only used at 40% but swap is already kick in
(I assume that was really 5 Gb.)
Swap is reserved but not allocated. Nothing is wrong.
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тАО04-07-2011 11:43 AM
тАО04-07-2011 11:43 AM
Re: RAM is only used at 40% but swap is already kick in
Oops, I guess it was really 5 Mb. This must be the type of pages that needed to be allocated and/or was swapped out at one time.
It is the 8 Gb that I mentioned that is reserved.
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тАО04-07-2011 12:40 PM
тАО04-07-2011 12:40 PM
Solution1) You had a spike in physical memory usage earlier which isn't happening now. The system will free swap when/if a previously paged object is removed - but it doesn't bother doing it if the memory is paged back in, especially if it is unmodified [as it saves a repeat I/O if a paging opportunity reoccurs]. Hence a spike in memory load can result in swap being used even with lots of free memory post-spike when you run the tools to observe things.
2) The system is actually under physical memory pressure now. This can happen if the memory load is primarily in User space and is yet another reminder that pseudo [memory] swap is *not* RAM and you shouldn't try to conflate the swapinfo output to RAM consumption. Consider -- you have 8Gb or so of disk swap reserved. You probably have around 8Gb or so of physical memory [I don't know your OS version, so I don't know the rough percentage your memory line represents relative to RAM... just go with the example 8Gb]. Say your SYS RAM load is 512Mb, leaving 7.5Gb for user space. If that 8Gb of user space virtual faults all of it in (or at least say a 7.5Gb SGA shared memory object), you will consume all of physical memory. swapinfo will still show the same reserve, and the memory line will only reflect the locked memory of the SYS usage. But paging will occur - because you're trying to use all of RAM. Typically, you shouldn't expect to run out of swap before you run out of RAM, after all.
3) You aren't under global system pressure but could be using PRM/WLM/gWLM/whatnot which has limited a workload to a smaller amount of memory -- resulting in just that workload being under memory pressure and needing to page.
What does vmstat say? Are there page outs? What version of the OS? Do you have Glance -- and if so, what does it report for physical memory usage?
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тАО04-07-2011 01:40 PM
тАО04-07-2011 01:40 PM
Re: RAM is only used at 40% but swap is already kick in
OS version:
HP-UX dbCus B.11.31 U 9000/800 2221170520 unlimited-user license
VMSTAT:
procs memory page faults cpu
r b w avm free re at pi po fr de sr in sy cs us sy id
2 1 0 706095 59875 0 0 1 0 0 0 0 1051 6820 654 1 2 97
GLANCE MEM REPORT:
Event Current Cumulative Current Rate Cum Rate High Rate
--------------------------------------------------------------------------------
Page Faults 3378 14488 767.7 376.3 842.5
Page In 880 3343 200.0 86.8 200.0
Page Out 0 0 0.0 0.0 0.0
KB Paged In 0kb 52kb 0.0 1.3 45.7
KB Paged Out 0kb 0kb 0.0 0.0 0.0
Reactivations 0 0 0.0 0.0 0.0
Deactivations 0 0 0.0 0.0 0.0
KB Deactivated 0kb 0kb 0.0 0.0 0.0
VM Reads 0 12 0.0 0.3 1.8
VM Writes 0 0 0.0 0.0 0.0
Total VM : 4.8gb Sys Mem : 16.0tb User Mem: 18.4gb Phys Mem : 8.0gb
Active VM: 1.1gb Buf Cache: 4mb Free Mem: 229mb FileCache: 3.0gb
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тАО04-07-2011 03:41 PM
тАО04-07-2011 03:41 PM
Re: RAM is only used at 40% but swap is already kick in
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тАО04-08-2011 02:24 AM
тАО04-08-2011 02:24 AM
Re: RAM is only used at 40% but swap is already kick in
Santa Claus came early this year and only told gpm? ;-)
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тАО04-08-2011 04:59 AM
тАО04-08-2011 04:59 AM
Re: RAM is only used at 40% but swap is already kick in
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тАО04-08-2011 05:05 AM
тАО04-08-2011 05:05 AM