+++ This bug was initially created as a clone of Bug #1656734 +++

Steps to reproduce:

1. Run https://testdrive-archive.azurewebsites.net/performance/fishbowl/

I can reproduce the slowness on Nightly81.0a1 Windows10 if WebRender on.
Webrender : 24fps/250fishes
Direct3D 11 (Advanced Layers) : 45fps/250fishes

WebRender on:
#1 Regression window (Webrender is enabled):
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=887408ca310cdf614d5ddb6f10f012aa9f1cf003&tochange=cd2634c753b9b955aafc290d57f0cbcdf9fab688
Regressed by: Bug 1592509

#2 Regression window(but gfx.webrender.compositor=false)
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=df4d3efbfa453cf1e0da54a44df349e130731f74&tochange=a22ce6ad4e273a47c9f4481e2462efa35b17d8eb
Regressed by: Bug 1547286

WebRender Off:
#3 Regression window(WebRender disabled i.e. Direct3D 11 (Advanced Layers)
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=df4d3efbfa453cf1e0da54a44df349e130731f74&tochange=a22ce6ad4e273a47c9f4481e2462efa35b17d8eb
Regressed by: Bug 1547286

Hey Alice, can you please post your gfx hardware section from about:support? Thanks!

(In reply to Jim Mathies [:jimm] from comment #1)

Hey Alice, can you please post your gfx hardware section from about:support? Thanks!

Attached in comment#0.

Graphics

Features
Compositing: WebRender
Direct2D: true
Uses Tiling (Content): true
Off Main Thread Painting Enabled: true
Off Main Thread Painting Worker Count: 3
Target Frame Rate: 60
DirectWrite: true (10.0.18362.1016)
GPU #1
Active: Yes
Description: AMD Radeon HD 6450
Vendor ID: 0x1002
Device ID: 0x6779
Driver Version: 15.301.1901.0
Driver Date: 2-26-2016
Drivers: aticfx64 aticfx64 aticfx64 amdxc64 aticfx32 aticfx32 aticfx32 amdxc32 atiumd64 atidxx64 atidxx64 atiumdag atidxx32 atidxx32 atiumdva atiumd6a atitmm64
Subsys ID: 23111787
RAM: 1024
GPU #2
Active: No
RAM: 0
Diagnostics
AzureCanvasBackend: direct2d 1.1
AzureCanvasBackend (UI Process): skia
AzureContentBackend: skia
AzureContentBackend (UI Process): skia
AzureFallbackCanvasBackend (UI Process): none
Display0: 1920x1080@60Hz
DisplayCount: 1
GPUProcessPid: 11084
GPUProcess: Terminate GPU Process
Device Reset: Trigger Device Reset
ClearType Parameters: Gamma: 2.2 Pixel Structure: RGB ClearType Level: 100 Enhanced Contrast: 300
Decision Log
HW_COMPOSITING:
available by default
D3D11_COMPOSITING:
available by default
DIRECT2D:
available by default
D3D11_HW_ANGLE:
available by default
GPU_PROCESS:
available by default
WEBRENDER:
opt-in by default: WebRender is an opt-in feature
available by user: Qualified enabled by pref
WEBRENDER_QUALIFIED:
available by default
WEBRENDER_COMPOSITOR:
available by default
WEBRENDER_PARTIAL:
available by default
WEBRENDER_ANGLE:
opt-in by default: WebRender ANGLE is an opt-in feature
available by user: Enabled
WEBRENDER_DCOMP_PRESENT:
opt-in by default: WebRender DirectComposition is an opt-in feature
available by user: Enabled
OMTP:
available by default
ADVANCED_LAYERS:
available by default
blocked by env: Blocked from fallback candidate by WebRender usage
WEBGPU:
disabled by default: Disabled by default