Severe Lag When Dragging Chrome/Warp-Terminal Windows with Mujoco Simulate Viewer Open, Possibly Related to Rendering or V-Sync

[tqolf]

Intro

Severe Lag and high CPU load

My setup

MuJoCo 2.3.3, Python
amd64, Linux/Ubuntu 22.04

What's happening? What did you expect?

1. When running the simulation with no other actions, CPU usage stays around 2-10%, and dragging the built-in Ubuntu terminal is still very smooth.
2. With the simulation running under default settings, dragging Chrome or Warp-Terminal results in CPU usage spiking to 80-100%, with severe lag. perf shows sched_yield accounting for over 80% of the CPU time.
3. When running the simulation with Vertical Sync disabled, CPU usage reaches 100%, but the lag when dragging Chrome/Warp-Terminal improves significantly, though there is still noticeable lag at the beginning of the drag.

Steps for reproduction

See

Minimal model for reproduction

Maybe unrelated to the model.

Code required for reproduction

Maybe unrelated.

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.

[yuvaltassa]

You are using a very old version. Does this also happen with latest MuJoCo?

[tqolf]

Yeah, there is a plan to upgrade, but we are still working on migration. Currently, we want to first understand what is causing this phenomenon.

[tqolf]

You are using a very old version. Does this also happen with latest MuJoCo?

I tried to upgrade, but the new code is very slow, elasped_time > 0.008

import mujoco
import mujoco.viewer

m = mujoco.MjModel.from_xml_path(xx)
d = mujoco.MjData(m)

viewer = viewer.launch_passive(m, d)
viewer.sync()

while viewer.is_running():
       last_time = time.time()
      # ...
      mujoco.mj_step(m, d)
      viewer.sync()

     elasped_time = time.time() - last_time
     if elasped_time < 0.001:
           await asyncio.sleep(0.001 - elasped_time)

[tqolf]

You are using a very old version. Does this also happen with latest MuJoCo?

And I have tried the latest MuJoCo, Severe Lag still exists when I draging Chrome/Warp-Terminal.

[yuvaltassa]

Can you please post a video of what you're seeing?

[tqolf]

Screencast.from.2024.10.14.21.30.15.webm

Can you please post a video of what you're seeing?

[tqolf]

You are using a very old version. Does this also happen with latest MuJoCo?

I tried to upgrade, but the new code is very slow, elasped_time > 0.008

import mujoco
import mujoco.viewer

m = mujoco.MjModel.from_xml_path(xx)
d = mujoco.MjData(m)

viewer = viewer.launch_passive(m, d)
viewer.sync()

while viewer.is_running():
       last_time = time.time()
      # ...
      mujoco.mj_step(m, d)
      viewer.sync()

     elasped_time = time.time() - last_time
     if elasped_time < 0.001:
           await asyncio.sleep(0.001 - elasped_time)

@yuvaltassa And How about this? When I use the old version, it's no need to call view.sync(). Also, the C++ version didn't require it and ran smoothly. Does python sync API synchronize all the data for rendering? Are there any alternative optimization methods?

[tqolf]

Screencast.from.2024.10.14.21.30.15.webm

Can you please post a video of what you're seeing?

And I use perf to analyze performance, sched_yield accounting for over 80% of the CPU time.

[yuvaltassa]

@saran-t might be able to help

[saran-t]

What GPU are you using?

[tqolf]

What GPU are you using?

CPU: 13th Gen Intel(R) Core(TM) i7-13700K
GPU: NVIDIA GeForce RTX 4060

And I think GPU is not releated to this problem, 'cause sched_yield too frequently and GPU usage is very slow