Comment 13 for bug 82528

I can confirm this on current gutsy. This is very annoying, makes using encrypted partitions nearly impossible (core2duo and 500GB sata disk). With the dual-core processor the computer actually performs fine, the wait-time reported by top is 50% as only one core is being hogged, but the write performance to a dm-crypt encrypted ext3 partition is absolutely horrible (I didn't measure but the average speed seemed to be below 1MB/s). The problem has nothing to do with encryption overhead itself, the computer is idling most of the time without any cpu-load and writing to hd only occasionally. Writing to a plain unencrypted partition is going >50MB/s on the same disk.

Interestingly, write performance is fine to the encrypted partition when there is some other writing going on to a plain ext3 partition at the same time.