https://issues.apache.org/bugzilla/show_bug.cgi?id=44938
Summary: the thread http-80-SendFile-0 consumes 100% of CPU and
slow tomcat responses
Product: Tomcat 6
Version: 6.0.14
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: Connectors
AssignedTo: [EMAIL PROTECTED]
ReportedBy: [EMAIL PROTECTED]
Created an attachment (id=21924)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=21924)
stack when the CPU is at 100%
Hi,
Tomcat version is: 6.0.14
APR: installed via RPM apr-1.2.8-6
Apache Tomcat Native library 1.1.10
APR capabilities: IPv6 [true], sendfile [true], accept filters [false], random
[true].
Linux version: 2.6.23.1-10.fc7 #1 SMP i686
JVM version: Java HotSpot(TM) Server VM (build 1.5.0_15-b04, mixed mode)
VM Options: -server -Djava.net.preferIPv4Stack=true -Xmn300m -Xms1280m
-Xmx1280m
i'm getting for weeks a problem, the tomcat consumes 100% of CPU for several
minutes and tomcat responses is too slow and sometimes blocking, i cant figure
what the problem until today, i manage to configure JConsole, to get that the
thread that consumes all my CPU for this long period is the http-80-SendFile-0.
i put a tcpdump capture, that capture all traffic in production and JConsole to
get exact time that the problem occurs, then on wireshark i see many TCP
checksum errors, i found a way to avoid checksum errors that is explained at:
http://wiki.wireshark.org/TCP_checksum_offload
since i think that the checksum isnt the real problem, because disabling the
checksum made by ethernet board, dont solved the problem, i do more research
and find something about TCP Window Scale Option explained on RFC 1323, and
something about a problem at http://groups.apu.edu/awg/node/101 with that
problems i run the follow command at Linux console:
sysctl -w net.ipv4.tcp_window_scaling=0
whit this appears that the APR dont consumes all CPU anymore, then my question
is, exists any know problem with APR and window scaling? or i'm get a wrong
idea of what is the real problem?
attached is the full stack when the CPU is consumed 100% by the
http-80-SendFile-0, the thread Stack is:
org.apache.tomcat.jni.Poll.poll(Native Method)
org.apache.tomcat.util.net.AprEndpoint$Sendfile.run(AprEndpoint.java:1748)
java.lang.Thread.run(Thread.java:595)
all errors "Error occurred during stack walking:" in the attached stack is:
java.lang.NullPointerException
at sun.jvm.hotspot.runtime.Frame.addressOfStackSlot(Frame.java:214)
at
sun.jvm.hotspot.runtime.x86.X86Frame.getEntryFrameCallWrapper(X86Frame.java:452)
at sun.jvm.hotspot.runtime.Frame.entryFrameIsFirst(Frame.java:379)
at sun.jvm.hotspot.runtime.Frame.isFirstFrame(Frame.java:154)
at sun.jvm.hotspot.runtime.VFrame.sender(VFrame.java:109)
at sun.jvm.hotspot.runtime.VFrame.javaSender(VFrame.java:134)
at sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:50)
at sun.jvm.hotspot.tools.JStack.run(JStack.java:41)
at sun.jvm.hotspot.tools.Tool.start(Tool.java:204)
at sun.jvm.hotspot.tools.JStack.main(JStack.java:58)
i really dont know if this is a tomcat BUG, or a problem with Linux/Firewalls
and routers, but i wish to share here what i found and how much time this
consumes to get a workaround.
KR
Clóvis
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