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Quite often, one of the applications I use freezes (“does not respond”) for a while, in extreme cases for few minutes. This happens especially when when switching apps. During this time, the HDD light flashes constantly and perfmon show that HDD is used 100% of the time (OTOH, CPU isn't) and that pagefile is being read (which is to be expected when switching apps), but at a very slow rate. When I sort the disk table in perfmon by read or write, the file read and wrote the most is the pagefile, but it's still quite low rate (I don't remember the numbers).

How can I diagnose what's causing this?

I use Windows Vista, and the computer is quite ordinary two years old laptop.

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How much memory does the machine have? Hard drive size? What kind of programs are you running when you have this problem? – Mokubai May 27 '10 at 14:38
2 GB of memory, 150 GB HDD. The programs I usually run when this happens are Firefox, Winamp, Visual Studio, avast. Firefox tends to use quite a lot of memory, right now, it's at 300 MB, sometimes it's even more. – svick May 27 '10 at 17:06

Do a memory check, using a memtest86+ boot disk. Verify the size detected is correct so you know that some of your RAM isn't dead. This may take a few hours so you can run it overnight and check the results in the morning if you like. If the memory is OK, then do a hard drive diagnostic with a MHDD boot disc. Since the hard drive is 150GB I assume that it's EIDE/PATA. If so you are looking for random read times under 150ms. If you see any odd blocks with times higher than that, especially if you see any that show up in red, then you may want to invest in a new hard drive. Bad memory can cause a false bad reading on MHDD so make sure you test the RAM first.

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Do you have your pagefile set to a specific size? You should leave it on "system managed" so that it can grow as needed.

Also, if you have I/O intensive applications running on the same disk that the pagefile is on, it will cause resource contention and reads/writes will be slow for both the pagefile and the other files that are being accessed.

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Currently, it's fixed at 3 GB, but I think it happened also when it was set on “system managed”. I don't have any I/O intensive applications I know of running at the time this happens. – svick May 27 '10 at 17:09 should do it

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If I understand it correctly, I should download the tool to analyze the issue, right? But… that matches the description the best is not for Vista. And the advice there is not very good (it's along the lines of “for faster pagefile, use faster disk”). – svick May 28 '10 at 2:12

How about pagefile fragmentation? If the pagefile was at one point system managed, it would have grown according to the needs of the system. It may have become fragmented in the process. If that if the reason, there is a simple way to solve it.
First make sure you have more than enough disk space for new page file. Then defragment you hard disk. After that disable the page file in windows settings and reboot. Then delete pagefile.sys. Remember to empty the recycle bin. Now just to be safe, defragment you hard drive one more time. After that reboot and set new pagefile size to the size you want it to be. System should now allocate entire pagefile in one fragment. It may improve performance.

Also when defragmenting, use a traditional program, like the one that comes with windows. More advanced programs like MyDefrag may leave empty space after a file to let it grow. That shouldn't be a problem, but I recommend against them in this case just so that windows doesn't try to fit new pagefile into small spaces between files.

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According to MyDerag, my pagefile has currently 128 fragments. That could be better, but I'm pretty sure it would cause so much performance loss. – svick Jul 11 '10 at 9:22
Wow! I'm shocked to see that large number of fragments. I think that's your biggest issue right now. Defragment pagefile as soon as possible. I was actually expecting you to have few fragments, but 128! That's in my opinion an enormous number. – AndrejaKo Jul 11 '10 at 9:32

the pagefile is not SLOW, if the OS is reading the pagefile, its because the ram is not enough for the opened apps.

what is slow is the disk. If you defragment the pagefile, the performance improvement will be minimum. you need more ram.

also, if you can pay the upgrade, Windows 7 have a much better memory management,

btw, disable Superfetch in services, it frees a lot of memory.

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check this guide, specially tweak 21-53 – Alex Angelico Feb 14 '11 at 1:06

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