maemo.org - Talk - View Single Post - How to free swap memory without rebooting?

Hacker	2013-03-21 , 16:15
Posts: 359 \| Thanked: 322 times \| Joined on Jun 2010	#6

Thanks for the responses! I have read and researched what everyone has said and here's some feedback.

Originally Posted by juiceme

Well, I don't use OC, I don't use FasterN9, and still I find the performace good all the time regardless of uptimes...
(well it's only 7 days now because I did some boot stuff back then... but generally I only boot my device when I need to change to different kernel/OS...)

I do not think you need to boot your devices regularily to have good performance. If that's required, then you have misbehaving applications or you have yourself done some tuning of the device that has turned sour.

Hmmm, given the number of users who use FasterN9, overclocking, etc., slow performance is an issue for many of us! Maybe you have an exceptional N9 or you have different expectations. :-) The problem is not misbehaving apps (I used top command and Conky to check); but rather it seems to be that swap memory is not being freed up even after the related apps are closed, so you eventually use more and more of the available swap memory, causing the N9 to slow down more and more.

The swap-related slowdown issue is discussed in this thread: http://talk.maemo.org/showthread.php?t=84007

I started this thread in hopes that an answer could be found to the swap-reset question. Once we have an answer, It can be merged in a solution thread.

Originally Posted by pichlo

I thought the whole idea of swapping is to put the less used memory blocks out of the way but have them ready when needed. Resetting the swap would mean that the next time the memory block is needed, it will have to be reinitialized again which is slower than fetching it from the swap. It is true that the swap space may become fragmented in which case a reset may help a little but you will get a better performance boost by closing applications to reduce the absolute memory usage.

Have you found this?

http://talk.maemo.org/showthread.php?t=84007

Yes, I have found that thread, and while your theory seems plausible, it clearly is not working out in real life because several users, including users in the thread that you quote, are having the same problem with swap-related issues! ;-) If the memory were behaving as expected and not causing slowdown, I suppose most of these types of threads would not exist. The problem, I think, is as I stated above: that even closing programs that caused the swap memory to be used does not free swap mem., so it is inevitably exhausted and leads to slower and slower performance.

Originally Posted by pichlo

You can reset the swap by running (as root)
Code:
swapoff -a
swapon -a
I won't recommend it though. I don't have an N9, but on my N900 this takes a LONG time (minutes) and results in some background tasks forcibly closed as they can't allocate memory while the swap is off.

This approach was discussed in the thread you quote and did not work. :-( Has anyone with an N9 used this approach successfully? I will run a confirmation study when I have a chance.

And thanks for the two swap spaces ideas and research threads. I'll check them out, but am still looking for a workable, easy swap reset approach that avoids reboot.

Mikkosssss and Lirion, I have tried Dropcache, but as discussed in the thread discussed above, it does not seem to solve the problem of freeing swap memory (though it is very useful in tracking the problem as it shows the amount of free swap memory).

Thanks again, everyone.

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