Btrfs + dm-crypt using only one CPU core

BlueFusion · Guru Joined: 08 Mar 2006 Posts: 371

I am running 4 hard drives and 1 SSD in my desktop with an i7-940 CPU. All of them are formatted with LUKS/dm-crypt with btrfs on top of them. There are 3 separate btrfs filesystems.

Running a btrfs scrub today, I noticed that the drives are only reading at about 30MB/sec. Looking into it, further, I discovered that there are multiple kworker threads running, but only one CPU core is being used for all of them, limiting the dm-crypt speed significantly.

Is there a way to have kworker utilize more than one CPU core? Or atleast different filesystems/disks per CPU?

I just upgraded today to kernel 3.18.0.

I am not upgrading to a CPU with AES-NI yet.
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i7-940 2.93Ghz | ASUS P6T Deluxe (v.1) | 24GB Triple Channel RAM | nVidia GTX660
4x 4TB Seagate NAS HDD (Btrfs raid5) | 2x 120GB Samsung 850 EVO SSD (Btrfs raid1)

BlueFusion · Guru Joined: 08 Mar 2006 Posts: 371

I should also mention that it seems to only be LUKS/dm-crypt causing the issue. A cat /dev/sda > /dev/null even during the scrub process allows full SATA-II speeds.
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i7-940 2.93Ghz | ASUS P6T Deluxe (v.1) | 24GB Triple Channel RAM | nVidia GTX660
4x 4TB Seagate NAS HDD (Btrfs raid5) | 2x 120GB Samsung 850 EVO SSD (Btrfs raid1)

BlueFusion · Guru Joined: 08 Mar 2006 Posts: 371

Bump. Anything I'm missing or do I just have to upgrade before Skylake comes out?
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i7-940 2.93Ghz | ASUS P6T Deluxe (v.1) | 24GB Triple Channel RAM | nVidia GTX660
4x 4TB Seagate NAS HDD (Btrfs raid5) | 2x 120GB Samsung 850 EVO SSD (Btrfs raid1)