Big speed difference for G1 vs. parallel GC

Mon Oct 31 19:52:06 UTC 2016

Hello,
Since this is measuring a short workload after vom startup it might not be the best benchmark, but then again throughput GC is expected to be faster than G1.
In the particular case however I guess you could tune G1 a bit to that workload. Did you check the verbose GC logs, and how many CPUs does Java see/use?

Gruss
Bernd
-- 
http://bernd.eckenfels.net

On Mon, Oct 31, 2016 at 8:38 PM +0100, "Peter" <graphhopper at gmx.de> wrote:

    Hi,

    I've stumbled today* over a big speed difference for code execution
    with G1 GC vs. parallel GC also in the latest JDK8 (1.8.0_111-b14).
    Maybe you have interests to investigate this. You should be able to
    reproduce this via:

    # setup

    git clone https://github.com/graphhopper/graphhopper

    wget
    http://download.geofabrik.de/europe/germany/bayern-latest.osm.pbf

    cd graphhopper

    # run measurement

    export JAVA_OPTS="-XX:+UseParallelGC -Xmx1000m -Xms1000m"

    # the graphhopper.sh script just makes the installation of maven and
    bundling the jar a bit simpler

    # you can also execute the tests in the class Measurement.java

    ./graphhopper.sh clean

    ./graphhopper.sh measurement berlin-latest.osm.pbf

    # now a measurement-<some date>.properties is created:

    grep routing.mean measurement-XY.properties

    Now this should print a line where the value is in ms. E.g. I get
    ~450ms for the parallel GC and ~780ms for G1GC (on an old laptop).
    When I increase the Xmx for the G1 run to 1400m the results do NOT
    get closer to parallel GC!

    Let me know if you need more information!

    Regards

    Peter

    *

    https://github.com/graphhopper/graphhopper/issues/854

    -- 
GraphHopper.com - fast and flexible route planning

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