Conemu: Windows 10 build 15002: high CPU usage in conhost.exe instances

[nta]

Versions

ConEmu build: 161206 x64
OS version: Windows 10 15002 x64
Used shell version (Far Manager, git-bash, cmd, powershell, cygwin, whatever): cmd w/ clink

Problem description

High CPU usage for conhost.exe instances running under ConEmu control (accumulating to a single core at 100%).

Steps to reproduce

1. Run Windows 10 Insider Preview 15002.
2. Open a console window while ConHostV2 is enabled (default).
3. Observe CPU usage in Task Manager.

Actual results

High CPU usage, mainly during processing of paint window messages (according to ETW trace).

Expected results

No idle CPU usage in conhost.exe instances.

Additional files

conemu.xml.txt

[Maximus5]

Conhost.exe is closed source Microsoft application. So I can't fix conhost's bugs.
@miniksa can you take a look at this? It's rather strange that conhost tries to paint anything utilizing CPU even its window is invisible!

Perhaps related: CPU and I/O consumption

[miniksa]

Hey @nta, @Maximus5,

I have an active bug right now related to the console trying to paint when it's been set to SW_HIDE with ShowWindow (or via the STARTUPINFO structures that set hidden/shown). It's MSFT: 10248233 and set for the Creators Update release. If this window is hidden with SW_HIDE, then I'm already working on a fix. But I'll check down our other shown/hidden code paths as well when I go through this bug in case it's getting triggered another route.

It will probably be a few weeks before this makes it out in an Insider build. I'll try to bump this thread when I get the fix checked in and it starts percolating up the source tree to main.

Thank you very much for the report!

--Michael

[miniksa]

Hi guys, I'm pretty sure this bug ended up being MSFT: 10243950 which was an issue with a runaway WM_PAINT message with ValidateRect in the console paint loop. That bug's fix is almost out to the insider branch (probably in the next week or so) which should resolve this issue.

Thanks,
--Michael

[miniksa]

This didn't make 15014. It should be in next week's build.

[gavin19]

It was still present in 15014 but it's fixed in 15019 on my machine.

This wasn't limited to ConEmu either. I had the same problem with other programs that spawned/used the Console Window Host process, like Photoshop/Visual Studio.

[alex17pat]

This worked for me and I want to share that.
step 1 – open service manager
step 2 – Now, click on services & applications and then click on services under it in the left menu.Scroll down and find superfetch in the right side.
Step 3- double click and stop the service and also choose startup type as disabled.
Source: http://merabheja.com/windows-10-high-cpu-and-ram-usage-problem-fix/