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I have a question for windows behavior. I was running a bunch of applications in my xp, they run smoothly at that moment. Then I leave my machine alone for some time, say a night, a few hrs, when I come back, the machine will be very slow (loading sth), for a few minutes, then it come smooth finally.

I would like to know why it would slow when I leave the machine idle for some time (surely not hiberate)

What does the windows scheduler do? I guess it is some of the memory allocation problem.

Thanks Kit

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up vote 3 down vote accepted

Could be power management turning your hard drives off after 30min, try experimenting with changing those settings, like making them a short time and see if the symptoms happen sooner, and try making them longer and see if the symptoms come in later. See if the symptoms match the time set there. I can't guarantee that that causes that symptom but perhaps it does. You'd find out if you try that test though.

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It might be easier to just set it to turn the drives off “Never” and then see if the delay still happens. – Synetech Feb 24 '12 at 3:05
If turning off the harddisk, why it would slow the windows? Cause i think that all my application running should be still in my RAM... – Kit Ho Feb 24 '12 at 3:08
Yes, but when you start using the computer again, the hard-drive is very likely to need to be used, so if Windows turned it off to save power, then it has to turn back on. This can take ~10 seconds for it to spin up and re-initialize. – Synetech Feb 24 '12 at 3:19
@KitHo besides (I suppose as mentioned) time for them to spin up.. it's also some may be in virtual memory(so on hard drive) if you have a lot open. Infact, here's kind of a theory not so relevant perhaps, but maybe if apps aren't used for a while they could get sent into virtual memory. – barlop Feb 24 '12 at 3:36

It sounds like the system is indeed defragmenting the drive while it’s idle. Once you press a key or mouse button, it may take Windows a moment or two to stop defragging. If it bothers you or is problematic, you can turn it off.

In Windows XP, you can edit the registry or just use TweakUI:

enter image description here

(In Windows Vista and up, you need to delete the task or uncheck the Run on schedule option in the Defrag program.)

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what does the defragging mean? – Kit Ho Feb 24 '12 at 3:05
The disk can become fragmented, so is set to automatically defragment the disk when the system is not being used to make the drive perform better. – Synetech Feb 24 '12 at 3:17
Yes! I found that the hard-disk LED will turn on when i return to the system? What are they acutally do? only defragmentation? – Kit Ho Mar 2 '12 at 17:20
Yes, it definitely sounds like Windows is defragmenting the system while it is idle (not doing anything / not being used). That’s usually a good thing because it gives better performance and makes data-recovery easier. If it bothers you though, you can turn it off. I’ll add steps in the answer. – Synetech Mar 2 '12 at 21:10

I would like to know why it would slow when I leave the machine idle for some time (surely not hiberate)

It is because the system was idle for a while, so Windows paged out the memory of most of your programs to disk. As a result, when you start using them again, it has to page all of that back into RAM which means that for a while (a few seconds to a few minutes depending on how much memory needs to be read and the speed of the disk and location of the swapfile), it will be slow and sluggish. Once the memory is read back into RAM from disk, the system should start getting more responsive again.

What does the windows scheduler do? I guess it is some of the memory allocation problem

The Task Scheduler is exactly what its name implies: it lets you schedule programs to be run at specific times or under specific circumstances, and then runs them. It has nothing to do with your issue.

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The only exact way to know is to view the task manager panel's process tab, sorted by CPU usage. Most likely a full disk scan by your virus checker is chugging along and takes a few seconds to shutdown.

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i don't have a virus check or disk scan. the application running should be the same. I want to know the behaviour of window schedulder a bit. would they put some of the appliction from RAM to disk?? – Kit Ho Feb 24 '12 at 2:39
The windows task scheduler has some things marrked to run at idle. If you check the task manager's process list, it will identify which one is running. That higher cpu task does need to shutdown, release its ram useage. If you don't have a virus checker, you might have some other issues, like some unwelcome trojan monitoring keystrokes. – jdh Feb 24 '12 at 2:46

The Windows task scheduler will run what ever you schedul it to run when you schedule it to run, it sounds to me like you are just wondering: IF windows is running something while you are away rather than: windows IS running something while you are away

Or atleast that is how I read your question, to answer my interpretation I don't believe there is anything that windows is doing; obviously the computer will go into some what of a 'sleep' state or "System Idle Process" if you will were it just sits there and twiddles it's thumbs.

My theory on the return to active duty delay (which most of us probably encounter) is that windows has to figure out where it left off especially if you left programs running and if they are 'heavy' programs at that it has to check all the RAM data and the exe's read HD's figure out graphics settings as it changes over from screen saver to the UI; your probably entering your password for user login so it has to check all that,

The list goes on, simply saying that even though all these sound simple (especially for a computer that has electrons flowing at the speed of light) however it still takes time; plus as the system sits idle it builds up heat heat slows the system down and so on.

Well that's my two cents worth, no official knowledge behind this one just a theory.

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