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Original cryptd thread implementation has scalability issue, this
patch solve the issue with a per-CPU thread implementation.

struct cryptd_queue is defined to be a per-CPU queue, which holds one
struct cryptd_cpu_queue for each CPU. In struct cryptd_cpu_queue, a
struct crypto_queue holds all requests for the CPU, a struct
work_struct is used to run all requests for the CPU.

Testing based on dm-crypt on an Intel Core 2 E6400 (two cores) machine
shows 19.2% performance gain. The testing script is as follow:

-------------------- script begin ---------------------------
#!/bin/sh

dmc_create()
{
        # Create a crypt device using dmsetup
        dmsetup create $2 --table "0 `blockdev --getsize $1` crypt cbc(aes-asm)?cryptd?plain:plain babebabebabebabebabebabebabebabe 0 $1 0"
}

dmsetup remove crypt0
dmsetup remove crypt1

dd if=/dev/zero of=/dev/ram0 bs=1M count=4 >& /dev/null
dd if=/dev/zero of=/dev/ram1 bs=1M count=4 >& /dev/null

dmc...