Try/Catch performance overhead

JavaScript performance comparison

Test case created by Marco Rogers

Info

Using try/catch inside of functions that allocate lots of variables introduces significant overhead. See this discussion related to node.js https://groups.google.com/forum/#!topic/nodejs-dev/E-Re9KDDo5w

Interestingly, other js engines don't have this overhead. All test runs have pretty uniform performance. But they are also significantly slower than the v8 control case.

Preparation code

<script>
  var tries = 10000;
 
  function test1() {
   function test(j) {
    var s = 0;
    for (var i = 0; i < j; i++) s = i;
    for (var i = 0; i < j; i++) s = i;
    for (var i = 0; i < j; i++) s = i;
    for (var i = 0; i < j; i++) s = i;
    return s;
   }
 
   test(tries);
  }
 
  function test2() {
   function test(j) {
    try {
     var s = 0;
     for (var i = 0; i < j; i++) s = i;
     for (var i = 0; i < j; i++) s = i;
     for (var i = 0; i < j; i++) s = i;
     for (var i = 0; i < j; i++) s = i;
     return s;
    }
    catch (ex) {}
   }
 
   test(tries);
  }
 
  function test3() {
   function test(j) {
    var s = 0;
    for (var i = 0; i < j; i++) s = i;
    for (var i = 0; i < j; i++) s = i;
    for (var i = 0; i < j; i++) s = i;
    for (var i = 0; i < j; i++) s = i;
    return s;
   }
 
   try {
    test(tries);
   }
   catch (ex) {}
  }
</script>

Test runner

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Testing in unknown unknown
Test Ops/sec
control - no try/catch
test1();
pending…
try/catch inside function
test2();
pending…
try/catch outside function
test3();
pending…

Compare results of other browsers

Revisions

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3 comments

DzungPro commented :

I see almost the testcases when using try-catch outside the function end up with higher speed. Does this mean using try-catch could speedup my code? Unreasonable!

sp8472 commented :

Flawed microbenchmark is flawed.

sanjay commented :

How is this possible. Try catch is never going to optimize the performance.

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