M.2 NVMe PCIe boot times much slower than old SATA SSD

Question

I've used dd to clone my old SATA SSD into a new and larger NVMe model on a Dell XPS 9360 and switched the SATA Configuration from the original RAID On to AHCI to get it booting. It works, but the new disk feels a lot slower than my old SSD, especially during boot. Boot times are up in the minutes vs the ~20 seconds I had before.

I've read somewhere that for M.2 NVMe PCIe chips it would be best for performance to switch SATA to Disabled instead of AHCI. Is that the case?

If it is, how can I safely switch modes? (I tried just switching it on the BIOS but the SSD isn't recognized and I can't boot from it).

If I should stick to AHCI, how can I get faster boot times? (Already enabled Fastboot in the BIOS)

Question originally asked (but considered off-topic) here

lshw:

$ sudo lshw

## output trimmed ##
*-pci:3
     description: PCI bridge
     product: Intel Corporation
     vendor: Intel Corporation
     physical id: 1d
     bus info: pci@0000:00:1d.0
     version: f1
     width: 32 bits
     clock: 33MHz
     capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
     configuration: driver=pcieport
     resources: irq:125 memory:dc200000-dc2fffff
   *-storage
        description: Non-Volatile memory controller
        product: Toshiba America Info Systems
        vendor: Toshiba America Info Systems
        physical id: 0
        bus info: pci@0000:3c:00.0
        version: 01
        width: 64 bits
        clock: 33MHz
        capabilities: storage pm msi pciexpress msix nvm_express bus_master cap_list
        configuration: driver=nvme latency=0
        resources: irq:16 memory:dc200000-dc203fff

## output trimmed ##

fdisk:

$ sudo fdisk -l
Disk /dev/loop0: 86,6 MiB, 90828800 bytes, 177400 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop1: 86,6 MiB, 90812416 bytes, 177368 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop2: 86,6 MiB, 90759168 bytes, 177264 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/nvme0n1: 953,9 GiB, 1024209543168 bytes, 2000409264 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: A4EB683B-DB3D-49FD-AA58-67970447597C

Device           Start        End    Sectors   Size Type
/dev/nvme0n1p1    2048    1050623    1048576   512M EFI System
/dev/nvme0n1p2 1050624    1550335     499712   244M Linux filesystem
/dev/nvme0n1p3 1550336 2000409230 1998858895 953,1G Linux filesystem


Disk /dev/mapper/sda3_crypt: 953,1 GiB, 1023413657088 bytes, 1998854799 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/mint--vg-root: 951,2 GiB, 1021388521472 bytes, 1994899456 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/mint--vg-swap_1: 1,9 GiB, 2021654528 bytes, 3948544 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

hdparm:

$ sudo hdparm -Tt --direct /dev/nvme0n1

/dev/nvme0n1:
 Timing O_DIRECT cached reads:   1952 MB in  2.00 seconds = 976.68 MB/sec
 Timing O_DIRECT disk reads: 2226 MB in  3.00 seconds = 741.09 MB/sec

$ sudo hdparm -Tt /dev/nvme0n1

/dev/nvme0n1:
 Timing cached reads:   16664 MB in  1.99 seconds = 8352.90 MB/sec
 Timing buffered disk reads: 2296 MB in  3.00 seconds = 765.09 MB/sec

lsb_release:

$ lsb_release -a
LSB Version:    core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch
Distributor ID: LinuxMint
Description:    Linux Mint 18.1 Serena
Release:    18.1
Codename:   serena

uname:

$ uname -a
Linux ricardo-ssd 4.4.0-128-generic #154-Ubuntu SMP Fri May 25 14:15:18 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Answer 1

Answer was simpler than I thought. This SSD had been dd'd from another laptop that had an offboard AMD GPU.

After I uninstalled the old Radeon drivers (following these instructions) boot times went back to normal.