Re: How to track down abysmal performance ata - raid1 - crypto -vg/lv - xfs

From: Mikael Abrahamsson
Date: Wed Aug 04 2010 - 07:53:17 EST

On Wed, 4 Aug 2010, Christoph Hellwig wrote:

The good news is that you have it tracked down, the bad news is that I know very little about dm-crypt. Maybe the issue is the single threaded decryption in dm-crypt? Can you check how much CPU time the dm crypt kernel thread uses?

I'm not sure it's that. I have a Core i5 with AES-NI and that didn't significantly increase my overall performance, as it's not there the bottleneck is (at least in my system).

I earlier sent out an email wondering if someone could shed some light on how scheduling, block caching and read-ahead works together when one does disks->md->crypto->lvm->fs, becase that's a lot of layers and potentially a lot of unneeded buffering, readahead and scheduling magic?

Mikael Abrahamsson email: swmike@xxxxxxxxx
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