**System Information**
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: GeForce GTX 660 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.87
**Blender Version**
Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-07-10 20:07, hash: `rBd2b910fafec6`
Same issue with blender-2.90.0-731d9f0bfa40-windows64 and 2.83.2 release
**Short description of error**
1. Grab brush do not use dyntopo even in dyntopo mode as you know. But it start to work very slow with dyntopo.
2. After I switch off dyntopo back, all brushes start to work very slow.
So to reproduce:
1. Zoom to heavy mesh.
2. Check speed of brushes on it.
3. Switch to dyntopo, use grab a little.
4. Switch back, check performance again.
{F8711884}