Cost of having try-catch statements?

Tue Aug 10 17:03:00 GMT 2004

Andrew Haley wrote:
> Martin Egholm Nielsen writes:
> > > > I was wondering: Is there any significant cost in having "unused" 
> > > > try-catches in my code?
> > > > That is, I have a method that 99.99% of the times invoked never throws a 
> > > > given exception. However, in case it does, I need to log it...
> > > The only cost is the unwinder tables, (which are not read into memory
> > > unless your exception is thrown) and the handler itself, which may
> > > cause some instruction cache presure.
> > So practically no overhead?
>> That's the idea. Really, if there is any significant overhead for an
> unused handler that would be a bug.

Being curious, I tried a micro benchmark (Main.java, attached).
The code just calls a method on an instance of class Main that then 
proceeds to call another method (that will never throw an exception, it 
simply increments a member to be not completely empty). In the first 
case there is nothing happening besides the second function being 
called, in the second case I have wrapped a try/catch around the call.
The time given is how long it takes to execute 10,000,000 calls in a for 
loop. Each test is repeated twice before any measurement takes place.
Here is the output (and what I did to compile the code):
----------------------------------------------------------------
C:\work\workspace-c++\MixAndMatch>gcj -o Main.exe -O2 Main.java --main=Main
C:\work\workspace-c++\MixAndMatch>Main.exe
without try/catch 250ms
with try/catch 1332ms
without try/catch 261ms
with try/catch 1322ms
C:\work\workspace-c++\MixAndMatch>javac Main.java
C:\work\workspace-c++\MixAndMatch>java -classpath . Main
without try/catch 80ms
with try/catch 321ms
without try/catch 70ms
with try/catch 320ms
C:\work\workspace-c++\MixAndMatch>gcj -o Main2.exe -O2 Main.class 
--main=Main
C:\work\workspace-c++\MixAndMatch>Main2.exe
without try/catch 311ms
with try/catch 1352ms
without try/catch 310ms
with try/catch 1342ms
----------------------------------------------------------------
This seems to indicate that in both gcj and J2SDK1.4.2_04 on Windows 
there is significant overhead. (And that the Sun JVM seems to be 4 times 
faster at this contrived "benchmark").
Harald
PS: I ran this on a 1GHz Centrino Notebook with 512mb Ram, CPU speed 
locked at 1GHz
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