Xephyr: Low FPS inside 3D accelerated games

I'm trying to use Xephyr to create a gaming multiseat setup. Inside the existing desktop environment, I'm running sudo Xephyr -softCursor -dpi 96 -screen 1440x900 -keybd evdev,,device=/dev/input/by-id/usb-Dell_Dell_USB_Keyboard-event-kbd,xkbrules=xorg,xkbmodel=evdev,xkblayout=latam -mouse evdev,,device=/dev/input/by-id/usb-0461_USB_Optical_Mouse-event-mouse :1. Then I place the Xephyr window in the second monitor in fullscreen. It used to work properly, but now for some reason I'm getting relatively low FPS inside Xephyr in 3D games. If I run them outside Xephyr they work properly. inxi -Fx relevant output: System: Host: Desktop Kernel: 4.4.39-1-MANJARO x86_64 (64 bit gcc: 6.2.1) Console: tty 2 Distro: Manjaro Linux Machine: Device: desktop System: Hewlett-Packard product: HP Compaq 8100 Elite SFF PC Mobo: Hewlett-Packard model: 304Ah BIOS: Hewlett-Packard v: 786H1 v01.05 date: 06/09/2010 CPU: Quad core Intel Core i5 760 (-MCP-) cache: 8192 KB flags: (lm nx sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx) bmips: 22353 clock speeds: max: 2933 MHz 1: 1733 MHz 2: 2933 MHz 3: 2933 MHz 4: 1733 MHz Graphics: Card: Advanced Micro Devices [AMD/ATI] RV710 [Radeon HD 4550] bus-ID: 01:00.0 Display Server: X.Org 1.18.4 driver: radeon Resolution: 1280x1024@75.02hz, 1440x900@59.90hz GLX Renderer: Gallium 0.4 on AMD RV710 (DRM 2.43.0 / 4.4.39-1-MANJARO, LLVM 3.9.0) GLX Version: 3.0 Mesa 13.0.2 Direct Rendering: Yes Running inxi -Fx inside Xephyr shows: GLX Renderer: Gallium 0.4 on llvmpipe (LLVM 3.9, 128 bits) Running glxinfo shows: Extended renderer info (GLX_MESA_query_renderer): Vendor: VMware, Inc. (0xffffffff) Device: llvmpipe (LLVM 3.9, 128 bits) (0xffffffff) Version: 13.0.2 Accelerated: no Video memory: 7923MB Unified memory: no Preferred profile: core (0x1) Max core profile version: 3.3 Max compat profile version: 3.0 Max GLES1 profile version: 1.1 Max GLES profile version: 3.0 OpenGL vendor string: VMware, Inc. OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 3.9, 128 bits) OpenGL core profile version string: 3.3 (Core Profile) Mesa 13.0.2 OpenGL core profile shading language version string: 3.30 OpenGL core profile context flags: (none) OpenGL core profile profile mask: core profile