Is log4net much slower than System.Diagnostics.Trace?

Question

I'm investigating the differences between using log4net and System.Diagnostics.Trace for logging, and I'm curious about the performance differences I've observed.

I created a test application to compare the performance of both logging methods in several scenarios, and I'm finding that log4net is significantly slower than the Trace class. For example, in a scenario where I log 1,000 messages with no string formatting, log4net's mean execution time over 1,000 trials is 9.00ms. Trace executes with a mean of 1.13ms. A lot of my test cases have a relatively large amount of variance in the log4net execution times; the periodic nature of outlier long executions seems to suggest GC interference. Poking around with CLR Profiler confirms there are a large amount of collections for a ton of log4net.Core.LoggingEvent objects that are generated (to be fair, it looks like Trace generates a ton of Char[] objects as well, but it doesn't display the large variance that log4net does.)

One thing I'm keeping in mind here are that even though log4net seems roughly 9 times slower than Trace, the difference is 8ms over 1,000 iterations; this isn't exactly a significant performance drain. Still, some of my expected use cases might be calling methods that are logging things hundreds of thousands of times, and these numbers are from my fast machine. On a slower machine more typical of our users' configurations the difference is 170ms to 11ms which is a tiny bit more alarming.

Is this performance typical of log4net, or are there some gotchas that can significantly increase log4net's performance?

(NOTE: I am aware that string formatting can alter the execution time; I am trying to compare apples to apples and I have test cases with no formatting and test cases with formatting; log4net stays as proportionally slow whether string formatting is used or not.)

The story so far:

• Robert Gould has the best answer to the question; I was mainly curious if it was typical to see log4net perform much slower than the Trace class.
• Alex Shnayder's answer is interesting information but doesn't really fall under the scope of the question. Half of the intent for introducing this logging is to assist in debugging both logical and performance problems on live systems; our customers put our products in many exotic scenarios that are often difficult to reproduce without expensive and large-scale hardware configurations. My main concern is that a large timing difference between "not logging" and "logging" could affect the system in such a way that bugs don't happen. In the end, the scale of the performance decrease is large but the magnitude is small, so I'm hoping it won't be a problem.

Answer 1

yes log4xxx is slower than trace, since trace is normally a near kernel tool, while log4xxx is a much more powerful tool. Personally I prefer log4xxx because of it's fexibility, but if you want something that doesn't impact as much, and you don't really need logs for production,say in debug only trace should be enough.

Note: I use log4xxx because the exact same applies to all languages with a log4 library not just .Net

Answer 2

you might be interested in the Common.Logging library. It's a thin abstraction wrapper over existing logging implementations and allows you to plug in any logging framework you like at runtime. Also it is much faster then System.Diagnostics.Trace as described in my blog post about performance.

hth, Erich

Answer 3

From my experience log4net performance isn't an issue in most cases. The real question is, why would you even need to "logging things hundreds of thousands of times" in a production system.
As I see it, in production you should log only bare minimum (info nd may be warning level), and only if need to (debugging an issue on site) should activate debugging at debug level.

Answer 4

If you want the best of both worlds, log4net will allow you to log to the aspnet tracer as well. I turn this option on when I want to get performance stats that are tied in to specific events in my logging.