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jakelandis / fsync_compare

Simple little application to compare fsync time between mmap vs. channel io for sequential writes
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Fsync Compare

Writes a 1GB file to compare write strategies (mmap vs. channel io) for append.

All times are in nano seconds.

Build from source:

mvn clean package
java -Xmx1024m -Djava.io.tmpdir=<some_path_that_is_not_tmp_fs> -jar target/fsync_compare-0.1-SNAPSHOT.jar

For example (from the included binary):

wget https://github.com/jakelandis/fsync_compare/raw/master/bin/fsync_compare-0.1-SNAPSHOT.jar
java -Xmx1024m -Djava.io.tmpdir=/storage -jar fsync_compare-0.1-SNAPSHOT.jar

The code uses Java's temp directory...but if that is a mapped to a temporary filesystem, then the results will be skewed badly.

You can also pass in either channel or mmap as an argument to just run one or the other, and get timings for the single run.

For example:

/usr/bin/time -v java -Djava.io.tmpdir=/apps -jar fsync_compare-0.1-SNAPSHOT.jar mmap