Why is exception handling expensive

The fix is to use [ Int The above tests are microbenchmarks. We started with an issue where we have data that we need to parse. The data contains some user input that is not parse-able for a variety of reasons. Each exception has some costs. We needed to find a way to handle this data without involving exceptions. TryParse turns out to be a method designed to solve our problem.

We ran some benchmarks to prove it. Check this: stackoverflow. If stacktrace is not important for you than you could try your idea but this could make debugging very hard if not impossible in some cases. Pshemo I don't plan to actually do this in code, I'm asking about the performance, and using this absurdity as an example where it could make a difference. MartinCarney I've added an answer to your last paragraph ie would caching an Exception have a performance gain.

If it's useful I can add the code, if not I can delete the answer. Show 1 more comment. Active Oldest Votes. Improve this answer. Mikhail Kholodkov The point here is that the statement "exceptions are expensive" is not really correct. A more correct statement is that exceptions 'can' be expensive. Honestly, I think saying only use exceptions for "truly exceptional cases" as in the article is too strongly worded.

They are perfect for pretty much anything outside the normal return flow and it's hard to detect the performance impact of using them this way in a real application. It might be worth it to quantify the overhead of exceptions.

Even in the very worst case reported in this rather exhaustive article throwing and catching a dynamic exception with a stacktrace that is actually queried, stack frames deep , takes 80 micro seconds. That can be significant if your system needs to process thousands of exceptions per second, but otherwise is not worth worrying about.

And that's the worst case; if your stacktraces are a little saner, or you don't query them stacktrace, we can process nearly a million exceptions per second. I emphasize this because many people, upon reading that exceptions are "expensive", never stop to ask "expensive compared to what", but assume that they are "expensive part of their program", which they very rarely are.

There is one part that is not mentioned here: the potential cost in preventing optimizations from being applied. For compiled methods real stack traces are reconstructed from virtual stack frame table stored as metadata. Show 2 more comments. Link to the constructor: docs. Add a comment. Theres a good write up on Exceptions here.

We can then use this to see what sort of costs different scenarios have The following are timings for Object creation alone. Time to create million String objects: Depth WriteStack ms! In both cases stack unwinding takes a large portion of the overall time. You can peek at the bytecode using javap javap -c -v -constants JavaException. Full Benchmark Code and Results. Up front I want to be clear that nothing in this post is meant to contradict the best-practices outlined in the.

Here are the full, raw results:. In the following graphs, shallow stack traces are in blue bars , medium in orange and deep stacks are shown in green. So we clearly see there is an extra cost for exception handling that increases the deeper the stack trace goes.

This is because when an exception is thrown the runtime needs to search up the stack until it hits a method than can handle it. The main cost is hidden in native fillInStackTrace method which walks through the call stack and collects all required information to build a stack trace: classes, method names, line numbers etc. Is throwing exceptions expensive C? Costs of Throwing Exceptions The first cost comes from simply having those extra constructs in your code: try and catch.

There is also the cost of cleaning up after the exception is thrown. While these costs aren't high because C is managed, they aren't free. Another cost comes from actually throwing the exception. What is try catch finally in C? The catch keyword indicates the catching of an exception. Are exceptions slow? Exceptions have a little bit overhead as long as they are never thrown.

As you see, the exceptions are really slow. Do not use them if they are thrown frequently. Do exceptions slow down code? Catching exceptions will slow down your code a lot, so it's very important to have a clear understanding of your error-handling strategy.