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From "David Cassidy" <david.cass...@db.com>
Subject Re: java Date related classes synchronization bottlenecks
Date Fri, 11 Jul 2003 08:59:03 GMT

I've done some tests with the below code
hope this helps

David

10 Processor Sun Sparc 2i 400Mhz (Solaris 2.8) jdk 1.4.0-b92

time java TestDatePerf  1 10000 real    0m2.096s user    0m1.901s sys     0m0.142s
time java TestDatePerf  2 10000 real    0m4.848s user    0m4.240s sys     0m1.372s
time java TestDatePerf  3 10000 real    0m7.449s user    0m6.530s sys     0m3.312s
time java TestDatePerf  4 10000 real    0m11.140s user   0m8.661s sys     0m4.543s
time java TestDatePerf  5 10000 real    0m13.194s user   0m11.001s sys     0m7.182s
time java TestDatePerf  6 10000 real    0m17.981s user   0m12.381s sys     0m8.602s
time java TestDatePerf  7 10000 real    0m20.659s user   0m15.271s sys     0m10.102s
time java TestDatePerf  8 10000 real    0m22.540s user   0m17.501s sys     0m13.603s
time java TestDatePerf  9 10000 real    0m26.457s user   0m19.991s sys     0m14.793s
time java TestDatePerf 10 10000 real    0m32.006s user   0m22.451s sys     0m15.923s
time java TestDatePerf 20 10000 real    0m57.951s user   0m43.660s sys     0m37.772s
time java TestDatePerf 30 10000 real    1m23.016s user   1m6.050s  sys     0m56.952s
time java TestDatePerf 40 10000 real    1m52.507s user   1m28.651s sys     1m15.832s
time java TestDatePerf 50 10000 real    2m21.881s user   1m49.161s sys     1m35.772s

linux dual 2.8Ghz P4  (kernel 2.4.19 ) jdk1.4.1_03-b02

time java TestDatePerf  1 10000  real    0m0.453s user    0m0.410s sys     0m0.020s
time java TestDatePerf  2 10000  real    0m1.411s user    0m1.390s sys     0m0.410s
time java TestDatePerf  3 10000  real    0m3.119s user    0m2.890s sys     0m1.610s
time java TestDatePerf  4 10000  real    0m3.690s user    0m3.040s sys     0m1.780s
time java TestDatePerf  5 10000  real    0m4.630s user    0m3.330s sys     0m2.360s
time java TestDatePerf  6 10000  real    0m5.410s user    0m4.530s sys     0m2.480s
time java TestDatePerf  7 10000  real    0m6.310s user    0m5.030s sys     0m3.000s
time java TestDatePerf  8 10000  real    0m7.330s user    0m5.510s sys     0m3.590s
time java TestDatePerf  9 10000  real    0m8.682s user    0m6.970s sys     0m4.060s
time java TestDatePerf 10 10000  real    0m9.648s user    0m7.730s sys     0m4.760s
time java TestDatePerf 20 10000  real    0m19.270s user    0m15.500s sys     0m9.210s
time java TestDatePerf 30 10000  real    0m32.570s user    0m26.940s sys     0m14.740s
time java TestDatePerf 40 10000  real    0m42.492s user    0m35.130s sys     0m20.560s
time java TestDatePerf 50 10000  real    0m57.209s user    0m47.040s sys     0m25.330s




                                                                                         
                                                                             
                      David Rees                                                         
                                                                             
                      <dbr@greenhydrant        To:       Tomcat Developers List <tomcat-dev@jakarta.apache.org>
                                                       
                      .com>                    cc:                                    
                                                                                
                                               Subject:  Re: java Date related classes synchronization
bottlenecks                                                     
                      11/07/2003 02:52                                                   
                                                                             
                      Please respond to                                                  
                                                                             
                      "Tomcat                                                            
                                                                             
                      Developers List"                                                   
                                                                             
                                                                                         
                                                                             
                                                                                         
                                                                             




On Thu, Jul 10, 2003 at 05:46:06PM -0500, Glenn Nielsen wrote:
>
> Now use jar to unarchive the src.jar file in your java SDK.
> Take a look at the java.sql.Timestamp.toString() method which the FileLogger
> above uses.
>
> To verify this look at the source for java.util.Date.getField().

Yes, that looks bad (looking at 1.4.2 src)!  It appears that avoiding calls to the
Timestamp.toString() is really to be avoided if possible.

> And there are many other synchronization bottlenecks in the following Date
> related classes:
>
> java.util.Calendar.getInstance()
> java.util.Date
> java.util.TimeZone.getDefault()
> java.sql.Date
> java.sql.Time
> java.sql.Timestamp

I took a look at some of these, these don't appear to be as bad as the
Timestamp.toString().

I did a quick google of Date performance issues and didn't find
anything.  Is this a well known bottleneck in multi-threaded
applications?

>   > Does a simple test case which simply starts up a number of threads which
>   > all use one of the classes shown below display the problem nicely?
>
> I am sure it would, I haven't had time to write one up yet.

I wrote a simple multithreaded program which makes calls to
Timestamp.toString() and varied the number of threads running and the
number of calls.  On a single CPU system (a Duron 600), scaling from
1-20 threads performed as I expected, with the 20 thread iteration
taking only slightly longer than the single thread iteration.

However, when running this on a dual-cpu system (PIII 500), going from
1 to 2 treads took over twice as long for the same overall number of
calls to Timestamp.toString().  From 4-20 threads overall time
slightly increased most likely due to the overhead of scheduling
multiple threads.

You must be running on a multiple-CPU system as it doesn't appear to be
a bottle-neck (except for the fact that it's a slow operation) on a
single-cpu machine and only one multi-cpu machines.

Given that this is the case, a temporary fix in your case would be to
run as many Tomcat's as you have processors on that particular machine
(assuming you have enough memory)

-Dave


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The following file(s) have been deleted by: David Cassidy on 11/07/2003 09:55:57

TestDatePerf.java
ATT1GXC9





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