Keeps utilising CPU core at 100%, and not finished syncing even after more than one hour. [GNU/Linux]

[dreirund]

Ahoj,

I use robrix version v1.0.0-alpha.1 on GNU/Linux, using your precompiled AppImage-build.

I have it now already run for over one hour, and it keeps utilising one CPU core at 100% (in top, I see a constant load of 102 .. 108%, so maybe one thread utilises one core fully and another thread is more or less idling around).

On the terminal, there is a continuous train of messages of the following kind:

2026-05-29T11:27:58.913390Z ERROR sync_once{conn_id="room-list" pos="<123456/s12345678_123456789_123456_12345678_1234567_1234_1234567_12345678_0_12345_2_1" timeout=0}:send{request_id="REQ-5068" method=POST uri="https://matrix.yatrix.org/_matrix/client/unstable/org.matrix.simplified_msc3575/sync" request_size="291.1k" status=200 response_size="451.9k" request_duration=2.222509034s}: matrix_sdk::http_client: Error while sending request: Api(Deserialization(Json(Error("invalid type: map, expected a string", line: 1, column: 336817))))
2026-05-29T11:27:58.919262Z ERROR matrix_sdk_ui::sync_service: Error while processing room list in sync service: Some(
    RoomList(
        SlidingSync(
            Http(
                Api(
                    Deserialization(
                        Json(
                            Error("invalid type: map, expected a string", line: 1, column: 336817),
                        ),
                    ),
                ),
            ),
        ),
    ),
)
2026-05-29T11:27:58.919896Z  INFO supervisor task: matrix_sdk_ui::sync_service: Entering the offline mode
[I] src/sliding_sync.rs:3498:13 - Received a sync service state update: Offline
2026-05-29T11:27:59.026750Z  INFO supervisor task: matrix_sdk_ui::sync_service: Exiting offline mode: None
[I] src/sliding_sync.rs:3498:13 - Received a sync service state update: Running

(The numbers behind pos=" I did change manually because I don't know if it is sensitive information.)

While I have learned here that those messages are most probably related to interaction between my homeserver and the Matrix Rust SDK, the 100% CPU core utilisation still is a major issue.

Also, in that over one hour of running, I did not seem to have gotten a full initial sync: I still miss a lot of spaces I am in, for example.

My system is a Intel Celeron N4100 system with 8 GiB of RAM.

Regards!

[kevinaboos]

Thanks for the bug report! I left a comment here as well.

One question: is your homeserver a custom one or the main matrix.org homeserver? If custom/self-hosted, does it support native simplified sliding sync? Can you login to it using Element X on either Android or iOS?

Robrix requires native simplified sliding sync, so if your homeserver doesn't have that, it would explain why syncing isn't working (though i'd expect to see an error about that somewhere in the log).

Either way, I do need more log details, preferably the full log if possible.

[dreirund]

Ahoj,

On Fri, 29 May 2026 11:05:20 -0700, Kevin Boos ***@***.***> wrote: One question: is your homeserver a custom one or the main matrix.org homeserver?

It is yatrix.org, it reports as Synapse version 1.152.1. Not self hosted by me.

does it support native simplified sliding sync?

I don't know, how can I check? I use "SchildiChat Desktop" as main Client.

Can you login to it using Element X on either Android or iOS?

I have none of those operating systems, but I know that someone could login to it using Element X.

[kevinaboos]

It is yatrix.org, it reports as Synapse version 1.152.1.

Ok thanks, yes that should support native sliding sync.

So the next step would be getting a full log to see what else might be going on.