Android: Vsync timestamps in the future

I have a kinda experimental setup as follows:

• android-x86, with Android S (preview 1)
• android.hardware.graphics.composer@2.3-service
• Baytrail platform
• mesa-21.1.0
• drm_hwcomposer from maurossi/blueprint_pie-x86_y21_w04
• gbm_gralloc
• client composition (vendor.hwc.backend_override = client)

It works almost fine, except I noticed some minor framerate drop. When this happens, I see the following warnings in the logs:

04-28 12:36:00.667  4124  4124 W Choreographer: Frame time is 0.70768 ms in the future!  Check that graphics HAL is generating vsync timestamps using the correct timebase.