Cannot seem to get good latency numbers!

Do "sudo dmesg | grep -i drm", you should get the driver used in plenty of lines

"lspci -vv" will list all your PCI devices and for each one, the last output line will give you the which kernel it's using

BTW, on this machine I have a Radeon RX550, it's using amdgpu driver. I assume it's just the name they use for the newest graphics cards they are selling. I don't think it's the privative module, here is a quote from wikipedia:

"AMDgpu is AMD's fully open source unified kernel driver for its GPUs on Linux. It takes the form of an in-tree kernel module."



About these latency spikes, I see you are using a 5.X kernel, I suggest to you to stick to the stable LCNC distro until you get more experience.

BTW, the huge increase in latency you got with that radeon card probably has something to do with power management. I just got an HD 6570 which ipso facto increased my latency on that system from 12 usec to 60+; using kernel boot parameter radeon.dpm=0, latency was again reduced to about 3 usec in a 15 minute test

Here are the results:
sudo dmesg | grep -i drm

sudo dmesg | grep -i drm
[    2.117990] ACPI: bus type drm_connector registered
[    2.739345] [drm] radeon kernel modesetting enabled.
[    2.740369] [drm] initializing kernel modesetting (RS780 0x1002:0x9616 0x1043:0x8388 0x00).
[    2.741881] [drm] Detected VRAM RAM=256M, BAR=256M
[    2.741882] [drm] RAM width 32bits DDR
[    2.741907] [drm] radeon: 256M of VRAM memory ready
[    2.741908] [drm] radeon: 512M of GTT memory ready.
[    2.741917] [drm] Loading RS780 Microcode
[    2.742020] [drm] radeon: power management initialized
[    2.742022] [drm] GART: num cpu pages 131072, num gpu pages 131072
[    2.753284] [drm] PCIE GART of 512M enabled (table at 0x00000000C0040000).
[    2.753511] [drm] radeon: irq initialized.
[    2.785511] [drm] ring test on 0 succeeded in 1 usecs
[    2.785798] [drm] ib test on ring 0 succeeded in 0 usecs
[    2.786256] [drm] Radeon Display Connectors
[    2.786257] [drm] Connector 0:
[    2.786258] [drm]   VGA-1
[    2.786259] [drm]   DDC: 0x7e40 0x7e40 0x7e44 0x7e44 0x7e48 0x7e48 0x7e4c 0x7e4c
[    2.786261] [drm]   Encoders:
[    2.786262] [drm]     CRT1: INTERNAL_KLDSCP_DAC1
[    2.786263] [drm] Connector 1:
[    2.786264] [drm]   DVI-D-1
[    2.786264] [drm]   HPD1
[    2.786265] [drm]   DDC: 0x7e50 0x7e50 0x7e54 0x7e54 0x7e58 0x7e58 0x7e5c 0x7e5c
[    2.786267] [drm]   Encoders:
[    2.786267] [drm]     DFP3: INTERNAL_KLDSCP_LVTMA
[    2.847315] [drm] fb mappable at 0xD0141000
[    2.847317] [drm] vram apper at 0xD0000000
[    2.847317] [drm] size 7299072
[    2.847318] [drm] fb depth is 24
[    2.847319] [drm]    pitch is 6912
[    2.847457] fbcon: radeondrmfb (fb0) is primary device
[    2.897196] radeon 0000:01:05.0: [drm] fb0: radeondrmfb frame buffer device
[    2.914709] [drm] Initialized radeon 2.50.0 20080528 for 0000:01:05.0 on minor 0
[    3.186363] [drm] amdgpu kernel modesetting enabled.
[    5.320147] systemd[1]: Starting Load Kernel Module drm...
[    5.338732] systemd[1]: This email address is being protected from spambots. You need JavaScript enabled to view it.: Deactivated successfully.
[    5.339011] systemd[1]: Finished Load Kernel Module drm.

lspci -vv

1:05.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RS780L [Radeon 3000] (prog-if 00 [VGA controller])
    Subsystem: ASUSTeK Computer Inc. RS780L [Radeon 3000]
    Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
    Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 0, Cache Line Size: 64 bytes
    Interrupt: pin A routed to IRQ 18
    NUMA node: 0
    Region 0: Memory at d0000000 (32-bit, prefetchable) [size=256M]
    Region 1: I/O ports at d000
    Region 2: Memory at feaf0000 (32-bit, non-prefetchable) [size=64K]
    Region 5: Memory at fe900000 (32-bit, non-prefetchable) [size=1M]
    Expansion ROM at 000c0000 [virtual] [disabled] [size=128K]
    Capabilities: <access denied>
    Kernel driver in use: radeon
    Kernel modules: radeon, amdgpu

So it appears that the current video card (onboard) is using the "radeon" driver. Is there an easy way to switch to another driver? I don't plan to mess with this video card but if I install the Radeon card and want to try a different driver it would be nice to know how. Will also be trying some kernel boot parameters as well.

Thanks

Hmmm. RS780L [Radeon 3000]. This is the integrated card, it isn't?

In that case, it could be that it needs the "radeon" module. Not sure about it. As I understand it, "amdgpu" is for the newest AMD graphic cards. But, since lspci -vv says it could work with both, you can give it a try. I guess your integrated card must be pretty new too, or amdgpu module couldn't drive it.

See, you'll find there is a package xserver-xorg-video-radeon and another package xserver-xorg-video-amdgpu. Uninstall xserver-xorg-video-radeon, this will make amdgpu the only module available in your system for your card, and it should use it automatically. Then see if it still works OK. If not, install it again and uninstall xserver-xorg-video-amdgpu.

I think this is the easiest way for you.

Yeah, it looks good. I'd love to know which motherboard it has

Hi
Could somebody please see the figures and guide me about my system latency :

Max Jitter for Servo Thread (1ms): is 332463
Max Jitter for Base Thread (25us): is 346784

Histogram is

Is it good , bad or ugly to use this computer. 

also set isolcpus=2,3 in your boot options. The 2.9 iso has grub-customizer included to simplify this

Can you please elaborate the process for a novice like me.
Thankyou