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From: Heinz Diehl <htd@fancy-poultry.org>
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Subject: Re: [dm-crypt] dm-crypt flush-to-disk freezes
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On 17.08.2010, Arno Wagner wrote: 

> What is the current take on this problem? Any fix 
> known or expected for the near future?

I don't know, and I'm not a VM proff either. That said, 
does it improve things when you write e.g. the following in your
sysctl.conf:

 vm.dirty_ratio = 10
 vm.dirty_background_ratio = 5

Or you could go even lower using

 vm.dirty_background_bytes = 134217728
 vm.dirty_bytes = 268435456

(but then without setting vm.dirty_ratio and vm.dirty_background).
It causes pdflush to write data more frequently and in smaller amounts,
thus reducing blocking via disk i/o.