Hello, dm-crypt in 2.6.38 changed to per-CPU workqueues to increase it's performance by parallelizing encryption to multiple CPUs. This modification seems to cause (massive) performance drops for multiple parallel dm-crypt instances... I'm running a 4-disk RAID0 on top of 4 independent dm-crypt(aes-xts) devices on a Core2Quad 3GHz. This setup did overcome the single-CPU limitation from previous versions and utilized all 4 cores for encryption. The throughput of this array drops from 282MB/s sustained read (dd, single process) with 2.6.37.3 down to 133MB/s with 2.6.38-rc8 (which nearly equals to single-disk throughput of 128MB/s - just in case this matters). This indicates way less parallelization now with 2.6.38 than before. I don't think this was intentional :) The dm-crypt per-CPU workqueues got introduced in 2.6.38 with c029772125594e31eb1a5ad9e0913724ed9891f2 Reverting dm-crypt.c to the version before this commit re-gains the same throughput as with 2.6.37. Submitters/Signers of c029772125594e31eb1a5ad9e0913724ed9891f2 CC:ed. Thanks for your work & regards Mario -- There are two major products that come from Berkeley: LSD and UNIX. We don't believe this to be a coincidence. -- Jeremy S. Anderson
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