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

[Mikael Abrahamsson <swmike swm pp se>]

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 swm pp se