Version is 1.1.1-4, latest from the maven.

I am using this version of your lib in android-project. Time of single calling org.slf4j.Logger.info method is about 4 milliseconds, appender seems like:

<appender name="trace" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${LOG_DIR}/trace.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
        <fileNamePattern>${LOG_DIR}/trace.log.%i.zip</fileNamePattern>
        <minIndex>1</minIndex>
        <maxIndex>10</maxIndex>
    </rollingPolicy>

    <triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
        <maxFileSize>1MB</maxFileSize>
    </triggeringPolicy>

    <encoder>
        <pattern>-------------------%n%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %msg%n-------------------%n%n</pattern>

        <immediateFlush>false</immediateFlush>
    </encoder>
</appender>

There is many calls of this method in performance-sensitive method, and sum of calling it taking about 20% of time of method execution. I guess, it happens cause there is synchronous method of writing, this is not surprising. In manual i found immediateFlush flag for encoder, i am tried to add it, but on the average there is no change in performance.

I guess the difference is must be here, isn't it? Maybe you can add some options for this flag, which can set the moment when deferred writing is happening?

PS: asynchronous method is not match for my situation, cause worker thread for this asynchronous writing is taking processor time, so asynchronous method works even slowly than synchronous one.