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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 18.08.2010, Milan Broz wrote: 

> What is the IO scheduler for the underlying device?
> (You can try deadline or cfq with some tuning - this is
> possible to tune online).

On my system, I get the best results with these (cfq):

echo "1" > /sys/block/sda/queue/iosched/low_latency
echo "8" > /sys/block/sda/queue/iosched/slice_idle
echo "8" > /sys/block/sda/queue/iosched/quantum

On some systems, things improve with slice_idle set to 0.