https://bz.apache.org/bugzilla/show_bug.cgi?id=64158
Bug ID: 64158
Summary: Tomcat 7 performance: remove enforcement that disable
keep-alive when busy threads go above
disable-keep-alive-percentage
Product: Tomcat 7
Version: trunk
Hardware: All
Status: NEW
Severity: normal
Priority: P2
Component: Catalina
Assignee: dev@tomcat.apache.org
Reporter: torres.y...@broadcom.com
Target Milestone: ---
Hi Tomcat,
During our performance testing, we found out another Tomcat 7 Acceptor
bottleneck, which is the Tomcat's fix to enforce busy-thread-ratio below
threshold (default appears to 75%) else disable-keep-alive. E.g.
org.apache.coyote.http11.Http11Processor#disableKeepAlive
This change was added in 2009 to lock-read worker size (in
JIoEndpoint#getCurrentThreadsBusy and later refactored to
AbstractEndpoint#getCurrentThreadsBusy).
https://github.com/apache/tomcat/commit/ecc2fb6f2ecb7f8cb51559adcfca82fa70b2bebf#diff-3253c70c8b90ec7cd422faf801dfa4f8
In Tomcat 6, there's no enforcement to disable keep alive when busy threads go
above disable-keep-alive-percentage.
In Tomcat 7, we're seeing added contention for the lock in
java.util.concurrent.ThreadPoolExecutor#mainLock. This cause more pressure on
get-pool-size which is also waiting for the same lock.
example stacktrace:
"tomcat-exec-executor-2@16852" daemon prio=5 tid=0x66 nid=NA runnable
java.lang.Thread.State: RUNNABLE
at
java.util.concurrent.ThreadPoolExecutor.getActiveCount(ThreadPoolExecutor.java:1830)
at
org.apache.catalina.core.StandardThreadExecutor.getActiveCount(StandardThreadExecutor.java:281)
at
org.apache.tomcat.util.net.AbstractEndpoint.getCurrentThreadsBusy(AbstractEndpoint.java:547)
at
org.apache.coyote.http11.Http11Processor.disableKeepAlive(Http11Processor.java:130)
at
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1096)
at
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:654)
at
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:317)
- locked <merged>(a org.apache.tomcat.util.net.SocketWrapper)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
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