DuckDB UI doesn't sleep well; excessive wakeups consume energy

[jwbee]

What happens?

I noticed that my Linux PC was a little hotter and louder than usual, considering that it was just sitting there. When I investigated it appeared that an idle duckdb CLI session has spawned many threads (66, on a 32-core host) and that collectively they cause many wakeups, which prevented the machine from entering a decent sleep state. The threads seem to enter and exit futex_wait quite rapidly.

This was observed with version DuckDB v1.3.2 (Ossivalis) 0b83e5d2f6

To Reproduce

duckdb

OS:

Linux Ubuntu 25.04

DuckDB Version:

DuckDB v1.3.2 (Ossivalis) 0b83e5d2f6

DuckDB Client:

CLI

Hardware:

AMD Ryzen 9 9950X

Full Name:

Jeff Baker

Affiliation:

self

What is the latest build you tested with? If possible, we recommend testing with the latest nightly build.

I have tested with a stable release

Did you include all relevant data sets for reproducing the issue?

Yes

Did you include all code required to reproduce the issue?

• Yes, I have

Did you include all relevant configuration (e.g., CPU architecture, Python version, Linux distribution) to reproduce the issue?

• Yes, I have

[jwbee]

Observations with powertop: idle system with duckdb running: > 300 wakeups/s; without duckdb: < 100/s.

The CPU time, to the extent any is being used, is going to AttachedDatabase::~AttachedDatabase. Again, this is an idle session.

[hannes]

Thanks for filing this, this seems like a bug - if the CLI is just sitting there it should not be doing anything.

[jwbee]

Updated observations: this only happens with the UI extension.

[Tishj]

Perhaps it's better suited for https://github.com/duckdb/duckdb-ui/issues then

[jwbee]

Quite so. Thanks for moving the issue to the right repo.

[jraymakers]

Thanks for the report; we'll look into what's causing this.

My initial guess is that it could be related to the polling the UI extension does to keep up-to-date about attached databases. If so, then setting ui_polling_interval to 0 should suppress this, at the cost of the UI not being updated when the databases change. Or, to continue allowing the UI to get updates, this can be set to a longer interval, at the cost of longer latency for the updates.