[Parallel-GS] [Sega Rally Championship (Japan)] Performance on modern Radeon graphics

Hello there,

Not that I'm into PS2 emulation, but I've been testing Sega Rally Championship (Japan) in latest git "ps2" core with Parallel-GS on AMD Ryzen 7 8700G which has Radeon 780 graphics, and it's as slow as on Intel XE graphics (ParallelGS being slow with Intel XE graphics is expected I believe?).

System information:

-GNU/Linux with 6.12.12 Debian Kernel
-RADV in latest stable MESA 25.0.0
-Latest stable labwc 0.8.3 Wayland compositor
-RetroArch and LRPS2 core built from latest GIT sources

Here's the MESA 25.0.0 configuration results in case I'm missing something obvious:

mesa 25.0.0

  Directories
    prefix                       : /usr/local
    libdir                       : lib/x86_64-linux-gnu
    includedir                   : include

  Common C and C++ arguments
    c_cpp_args                   : -mtls-dialect=gnu2

  OpenGL
    OpenGL                       : YES
    ES1                          : YES
    ES2                          : YES
    Shared glapi                 : YES
    GLVND                        : YES

  DRI
    Platform                     : drm
    Driver dir                   : /usr/local/lib/x86_64-linux-gnu/dri

  GLX
    Enabled                      : NO
    Provider                     : None

  EGL
    Enabled                      : YES
    Drivers                      : builtin:egl_dri2 builtin:egl_dri3
    Platforms                    : wayland surfaceless drm

  GBM
    Enabled                      : YES
    Backends path                : /usr/local/lib/x86_64-linux-gnu/gbm

  Vulkan
    Drivers                      : amd
    Platforms                    : wayland surfaceless drm
    ICD dir                      : share/vulkan/icd.d
    Intel Ray tracing            : NO

  Video
    Codecs                       : h264dec h265dec vc1dec
    APIs                         : va vulkan

  LLVM
    Enabled                      : YES
    Version                      : 17.0.6

  Gallium
    Enabled                      : YES
    Drivers                      : radeonsi zink
    Platforms                    : wayland surfaceless drm
    Frontends                    : mesa va
    Off-screen rendering (OSMesa): NO
    HUD lm-sensors               : NO

  Perfetto
    Enabled                      : NO

  Teflon (TensorFlow Lite delegate)
    Enabled                      : NO

  User defined options
    buildtype                    : release
    gallium-drivers              : radeonsi,zink
    glvnd                        : enabled
    glx                          : disabled
    platforms                    : wayland
    video-codecs                 : h264dec,h265dec,vc1dec
    vulkan-drivers               : amd

More on what's being used here:

~$ vulkaninfo |grep RADV
'DISPLAY' environment variable not set... skipping surface info
                GPU id = 0 (AMD Radeon Graphics (RADV PHOENIX))
GPU id : 0 (AMD Radeon Graphics (RADV PHOENIX)):
        deviceName        = AMD Radeon Graphics (RADV PHOENIX)
        driverID                                             = DRIVER_ID_MESA_RADV

So, isn't the Radeon 780m in the 8700G up to the task? It's supposed to have the same performance that an RTX2050, so it seems strange to me.

Maybe this game does something "special" that affects the Parallel-GS renderer or makes it work in a strange way?

NOTE: Initially I though this affecting all games, but only Sega Rally Championship (Japan) seems affected by this massive Parallel-GS slowdown.

Start by reproducing Sega Rally Championship (Japan) with the Parallel-GS renderer on the Radeon 780M/RADV setup described, then compare its performance with other games and graphics hardware. Done means identifying whether the slowdown is game-specific or renderer-related and documenting a measured fix or confirmed limitation.