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Date: Thu, 14 May 2009 08:34:44 -0400
From: David kerber <dckerber@verizon.net>
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Subject: Peformance on socket reads
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This post is a follow-on to my "performance with many small requests" 
thread from a couple days ago.

I have been watching my app, and taking thread dumps when things seem to 
be running a bit slower than I would like.  Right now, the biggest 
bottleneck seems to be on the POST data read.  Here is the thread dump 
of interest (there are several identical ones in my full dump):

[2009-05-13 15:49:50] [info] "http-1024-Processor11"
[2009-05-13 15:49:50] [info] daemon
[2009-05-13 15:49:50] [info] prio=6 tid=0x26c97858
[2009-05-13 15:49:50] [info] nid=0xe18
[2009-05-13 15:49:50] [info] runnable
[2009-05-13 15:49:50] [info] [0x2761f000..0x2761fa64]
[2009-05-13 15:49:50] [info]     at 
java.net.SocketInputStream.socketRead0(Native Method)
[2009-05-13 15:49:50] [info]     at 
java.net.SocketInputStream.read(Unknown Source)
[2009-05-13 15:49:50] [info]     at 
org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:747)
[2009-05-13 15:49:50] [info]     at 
org.apache.coyote.http11.InternalInputBuffer$InputStreamInputBuffer.doRead(InternalInputBuffer.java:777)
[2009-05-13 15:49:50] [info]     at 
org.apache.coyote.http11.filters.IdentityInputFilter.doRead(IdentityInputFilter.java:115)
[2009-05-13 15:49:50] [info]     at 
org.apache.coyote.http11.InternalInputBuffer.doRead(InternalInputBuffer.java:712)
[2009-05-13 15:49:50] [info]     at 
org.apache.coyote.Request.doRead(Request.java:423)
[2009-05-13 15:49:50] [info]     at 
org.apache.catalina.connector.InputBuffer.realReadBytes(InputBuffer.java:283)
[2009-05-13 15:49:50] [info]     at 
org.apache.tomcat.util.buf.ByteChunk.substract(ByteChunk.java:404)
[2009-05-13 15:49:50] [info]     at 
org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:298)
[2009-05-13 15:49:50] [info]     at 
org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:192)
[2009-05-13 15:49:51] [info]     at 
eddsrv.EddRcvr.processRequest(EddRcvr.java:198)
[2009-05-13 15:49:51] [info]     at eddsrv.EddRcvr.doPost(EddRcvr.java:99)
[2009-05-13 15:49:51] [info]     at 
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
[2009-05-13 15:49:51] [info]     at 
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
[2009-05-13 15:49:51] [info]     at 
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
[2009-05-13 15:49:51] [info]     at 
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
[2009-05-13 15:49:51] [info]     at 
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
[2009-05-13 15:49:51] [info]     at 
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
[2009-05-13 15:49:51] [info]     at 
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
[2009-05-13 15:49:51] [info]     at 
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
[2009-05-13 15:49:51] [info]     at 
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
[2009-05-13 15:49:51] [info]     at 
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
[2009-05-13 15:49:51] [info]     at 
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
[2009-05-13 15:49:51] [info]     at 
org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:667)
[2009-05-13 15:49:51] [info]     at 
org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
[2009-05-13 15:49:51] [info]     at 
org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
[2009-05-13 15:49:51] [info]     at 
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
[2009-05-13 15:49:51] [info]     at java.lang.Thread.run(Unknown Source)
[2009-05-13 15:49:51] [info]


The line eddsrv.EddRcvr.processRequest(EddRcvr.java:198) points to my 
InputStream.read() line.  All these variables are declared locally in 
the method doing the work, not at the class level, so there is no 
synchronization needed on them.  This method is called from the doPost() 
method of the servlet class.

Here are a few code lines for context setting:

req is my HttpServletRequest
iStream is a ServletInputStream


Then I have:

   len = req.getContentLength();
   b = new byte[ len ];
   iStream = req.getInputStream();
    /* this is the line 198 that the above thread dump is waiting for: */
   strLen = iStream.read( b, 0, len );
   iStream.close();


And then I convert b to a string and finish processing.  Is there 
anything stupid I'm missing that would cause the .read() to be slow?  Or 
is it just that my OS tcp/ip stack and/or network infrastructure appear 
to be slow?  I did quite a bit of reading on InputStream performance, it 
couldn't find any suggestions to improve on what I've already got (the 
biggest one was to read the whole thing at once rather than 
byte-by-byte, and I'm already doing that).

Thanks!
Dave


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