I am not sure about how the SLF4J solved that issue, but for the reference check the following link. i have copied the text below that explains how you can improve the performance by using the SLF4J.

http://www.slf4.org/faq.html#logging_performance
——————————————————————————
What is the fastest way of (not) logging?

SLF4J supports an advanced feature called parameterized logging which can significantly boost logging performance for disabled logging statement.

For some Logger logger, writing,

logger.debug(“Entry number: ” + i + ” is ” + String.valueOf(entry[i]));

incurs the cost of constructing the message parameter, that is converting both integer i and entry[i] to a String, and concatenating intermediate strings. This, regardless of whether the message will be logged or not.

One possible way to avoid the cost of parameter construction is by surrounding the log statement with a test. Here is an example.

if(logger.isDebugEnabled()) {
logger.debug(“Entry number: ” + i + ” is ” + String.valueOf(entry[i]));
}

This way you will not incur the cost of parameter construction if debugging is disabled for logger. On the other hand, if the logger is enabled for the DEBUG level, you will incur the cost of evaluating whether the logger is enabled or not, twice: once in debugEnabled and once in debug. This is an insignificant overhead because evaluating a logger takes less than 1% of the time it takes to actually log a statement.

Better yet, use parameterized messages

There exists a very convenient alternative based on message formats. Assuming entry is an object, you can write:

Object entry = new SomeObject();
logger.debug(“The entry is {}.”, entry);

After evaluating whether to log or not, and only if the decision is affirmative, will the logger implementation format the message and replace the ‘{}’ pair with the string value of entry. In other words, this form does not incur the cost of parameter construction in case the log statement is disabled.

…
…

log5j
or
http://www.slf4j.org/manual.html#typical_usage

private static final Log log = …
private static final boolean debugEnabled = log.isDebugEnabled();

/* instructions */
if(debugEnabled) {
log.debug(“hey”);
}
/* instructions */
if(debugEnabled) {
log.debug(“ho”);
}
/* instructions */
if(debugEnabled) {
log.debug(“foo”);
}