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тАО02-02-2010 01:15 PM
тАО02-02-2010 01:15 PM
Below is the swapinfo output.
# swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 8192 2634 5558 32% 0 - 1 /dev/vg00/lvol2
dev 16384 2635 13749 16% 0 - 1 /dev/vg00/lvol10
dev 8192 2634 5558 32% 0 - 1 /dev/vg00/lvol11
reserve - 15251 -15251
memory 15555 4296 11259 28%
total 48323 27450 20873 57% - 0 -
This is in V3 system in which pseudo swap is enabled by default. But the above swapinfo out put shows that using swap space. How to instruct my system to use physical memory? This is oracle database system.
Thanks
Davis Paul.
Solved! Go to Solution.
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тАО02-02-2010 01:56 PM
тАО02-02-2010 01:56 PM
Re: swap usage in V3
You need to add more RAM or reduce the load. Reducing the load may be on the user side (did you set the SGA too large? Running too many DB connections?) or may be on the kernel side (what's filecache_min / filecache_max? Are you using direct I/O for the oracle transactions [in which case, the filecache is less important and should be reduced]? Are you using VxFS and have you checked the value of vx_ninode (see such links as http://docs.hp.com/en/5992-3364/apbs02.html )?
Your memory line does indicate not that much of this should be kernel dynamic memory [so the vx_ninode may be a factor, but not enough of one]. Those allocations will be considered locked and hence borrow from memory swap. With only 4296Mb of memory swap consumed, it isn't 7Gb of kernel consumption that's your problem -- so you should check file cache and user space loads first (and likely the latter -- too big of an SGA or too many clients).
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тАО02-02-2010 06:19 PM
тАО02-02-2010 06:19 PM
Re: swap usage in V3
It is better to have everything in primary swap and yours is into 24 gb of 2ndary swap. Not good. However, 8GB is a lot of primary swap. You can play around with this formula and see if changing maxswapchunk helps.
Use this formula for to determine primary swap.
MaxSwap=maxswapchunks*1024*swchunk
Let say I increased maxswapchunk to 2048. BTW swchunk is set at 2048 (no need to change this). With that..
(2048*1024*2048)/1024=4194304 KB
ie 4096MB So the max amount of swap I can configure is 4GB.
vxinnode is not the problem here, his RAM is 16 GB. The forumla provided is for 3 GB.
More than likely your application, is this SAP, has set up a huge amount of cache within the SGA and it needs to be reduced.
I would look at the application being uses and see about reducing its cache, sga, shared memory consumption.
What is po in vmstat? Is is above 0? If so then you are certainly paging.
Adding more memory would make this a faster box if you can't reduce your 2ndary swap.
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тАО02-02-2010 06:38 PM
тАО02-02-2010 06:38 PM
Re: swap usage in V3
My personal opinion --- Baloney!
It does not matter HOW you lay out swap. If you start paging out to any significant degree, performance will SUCK!
To paraphrase A. Clay Stephenson: Worrying about swap layout is like rearranging the deck chair on the Titanic. It's basically pointless.
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тАО02-02-2010 10:13 PM
тАО02-02-2010 10:13 PM
Re: swap usage in V3
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тАО02-02-2010 10:42 PM
тАО02-02-2010 10:42 PM
Re: swap usage in V3
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тАО02-03-2010 12:48 AM
тАО02-03-2010 12:48 AM
Re: swap usage in V3
That's exactly Clay's and Patrick's points. You don't want to swap at all. By the time it decides to use primary or secondary swap, it is already orders of magnitude too slow.
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тАО02-03-2010 05:39 AM
тАО02-03-2010 05:39 AM
Re: swap usage in V3
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тАО02-03-2010 06:17 AM
тАО02-03-2010 06:17 AM
Re: swap usage in V3
No, the subject is "swap usage in V3."
The main question is: "How to instruct my system to use physical memory?" Which has been answered.
Unless you're reading something different than I am.
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тАО02-03-2010 06:59 AM
тАО02-03-2010 06:59 AM
Re: swap usage in V3
Of course, disk speeds are meaningless if you are not using swap space except for reservation. You don't want processes to ever be paged out if performance is a important.
Now that said, you might have a database engine that fits nicely into RAM but there are 500 interactive users all around the world. They type some data into the system every few minutes but their programs are idle (waiting to do something) for at least 50% of the workday. In that case, those programs can indeed be paged out and then recalled when necessary. There is a slight delay (a second or two) as each program is brought back but no delay while it is in use.
Bill Hassell, sysadmin