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Posted to users@tomcat.apache.org by William Crowell <WC...@perforce.com.INVALID> on 2025/04/07 18:28:46 UTC
Headless Mode
I am running Apache Tomcat 9.0.97 on Windows Server 2022 using Oracle’s JDK 1.8.0_441-b07. Anytime I generate a thread dump I see an AWT-Windows thread. Should this thread not be there when I am specifying the JVM to run in headless mode?
-Djava.awt.headless=true
This thread sits in a loop waiting for events which would take up CPU. Maybe I am misunderstanding that JVM option?
Regards,
William Crowell
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Re: Headless Mode
Posted by William Crowell <WC...@perforce.com.INVALID>.
Chuck,
Thanks for your reply. No wonder I was not seeing this thread in dumps of newer JVMs. I wonder when that was removed?
Regards,
William Crowell
From: Chuck Caldarale <n8...@gmail.com>
Date: Monday, April 7, 2025 at 3:49 PM
To: Tomcat Users List <us...@tomcat.apache.org>
Subject: Re: Headless Mode
> On 2025 Apr 7, at 13:28, William Crowell <WC...@perforce.com.invalid> wrote:
>
> I am running Apache Tomcat 9.0.97 on Windows Server 2022 using Oracle’s JDK 1.8.0_441-b07. Anytime I generate a thread dump I see an AWT-Windows thread. Should this thread not be there when I am specifying the JVM to run in headless mode?
> -Djava.awt.headless=true
>
> This thread sits in a loop waiting for events which would take up CPU. Maybe I am misunderstanding that JVM option?
Even in headless mode, the JVM must be able to do some graphics processing (such as image processing), and the old AWT framework is still needed for that. Looks like newer levels of the JVM (I’m using 23) have removed that AWT thread, so you might want to consider upgrading someday…
- Chuck
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Re: Headless Mode
Posted by Chuck Caldarale <n8...@gmail.com>.
> On 2025 Apr 7, at 13:28, William Crowell <WC...@perforce.com.invalid> wrote:
>
> I am running Apache Tomcat 9.0.97 on Windows Server 2022 using Oracle’s JDK 1.8.0_441-b07. Anytime I generate a thread dump I see an AWT-Windows thread. Should this thread not be there when I am specifying the JVM to run in headless mode?
> -Djava.awt.headless=true
>
> This thread sits in a loop waiting for events which would take up CPU. Maybe I am misunderstanding that JVM option?
Even in headless mode, the JVM must be able to do some graphics processing (such as image processing), and the old AWT framework is still needed for that. Looks like newer levels of the JVM (I’m using 23) have removed that AWT thread, so you might want to consider upgrading someday…
- Chuck
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Re: Headless Mode
Posted by Christopher Schultz <ch...@christopherschultz.net>.
William,
On 4/7/25 2:28 PM, William Crowell wrote:
> I am running Apache Tomcat 9.0.97 on Windows Server 2022 using Oracle’s JDK 1.8.0_441-b07. Anytime I generate a thread dump I see an AWT-Windows thread. Should this thread not be there when I am specifying the JVM to run in headless mode?
> -Djava.awt.headless=true
>
> This thread sits in a loop waiting for events which would take up CPU. Maybe I am misunderstanding that JVM option?
That thread probably uses 0% CPU. IT's blocking, waiting for events and
other things that need to happen "on the AWT thread". My guess is that
those events will never actually occur, so the thread does take up some
memory but should not otherwise impact performance.
-chris
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