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From Mark Thomas <ma...@apache.org>
Subject Re: tomcat thread incurring CPU load
Date Mon, 18 Nov 2019 14:14:55 GMT
On 18/11/2019 12:06, M. Manna wrote:
> Mark and others,
> 
> On Mon, 18 Nov 2019 at 12:01, Mark Thomas <markt@apache.org> wrote:
> 
>> OK, it looks like I can reproduce this.
>>
>> Steps to reproduce:
>>
>> - Windows 2016 Server fully patched
>> - Java 1.8.0u144
>> - Install Tomcat 8.5.45 from windows installer
>> - Add tcnative-1.dll (64-bit) from Tomcat Native 1.2.23
>> - Modify server.xml to use Http11AprProtocol on port 8080
>> - Make a single request
>>
>> I then see 1 core running at 100% until the connection times out after
>> 20s. Make another request and a core goes back up to 100% for 20s (the
>> default keep-alive time out).
>>
> 
>  I have also successfully reproduced this with making a single request
> (sorry for not replying in the weekend). Not sure how your graph looked
> like, but the Jvisualvm showed me a Sinusoidal modulation curve as soon as
> the request hit the server. and it didn't go down at all.

I see similar behaviour on Windows 7 but the the CPU usage drops after ~5s.

A binary search indicates that the issue was introduced with this commit:

https://github.com/apache/tomcat/commit/fffb08790e642e03f00c5f96a3a61ee09a2c8342

(this is for 9.0.x - 8.5.x and 7.0.x had similar commits)

However, that code was removed when APR was switched to a single poll
set. Also, that the issue does not happens on all platforms (I can't
repeat this on Linux) suggests the issue may not be in Java code.

More research required...

Mark

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