[Bug 1316] New: bootstrap builds compile too much

[bugzilla-daemon at icedtea.classpath.org]

http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=1316

            Bug ID: 1316
           Summary: bootstrap builds compile too much
    Classification: Unclassified
           Product: IcedTea
           Version: 6-hg
          Hardware: all
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Bootstrapping
          Assignee: gnu.andrew at redhat.com
          Reporter: stefan at complang.tuwien.ac.at
                CC: unassigned at icedtea.classpath.org

At some point in time I noticed that in icedtea6 builds without
--disable-bootstrap, almost all intermediate javac invocations during the first
phase (the build of openjdk.build-ecj) started taking much longer than what I
was used to. This was especially noticeable on my SheevaPlug when a normal
build (with --disable-bootstrap) took less then 5 hours, whereas a bootstrap
build took more than 4 days.

I just decided to investigate a bit further and dug out an old version of
icedtea6 (it says 1.11pre), and tracked a specific compilation step, comparing
run time and output files. Below are 3 such configurations for comparison. The
measurements were done on a quad core x86_64 server and with --enable-cacao.
With Hotspot builds, the behavior stays the same though. The exact commands
used were obtained from the respective build logs. Details below.

1: recent (f6a0a42bf443), --disable-bootstrap: 10 cpu secs, 976 output files
2: recent (f6a0a42bf443), --enable-bootstrap: 24 cpu secs, 6415 output files
3: ancient (fc898988b053), --enable-bootstrap: 4 cpu secs, 36 output files

I noticed that the recent builds use the system Java (Hotspot) for running
javac, while the ancient one uses gij/ecj.

The 1000 output files with javac vs. 36 with ecj don't bother me that much.
These builds complete in an acceptable amount of time. But with the >6400
output files case, something just doesn't seem right. These compile steps take
around 35 mins on the SheevaPlug (Fedora 17) because they use the
system-supplied OpenJDK Zero to drive javac.

The slow builds are also noticeable in icedtea7, but I did not experiment with
this configuration as comprehensively.

Details:

Build 1:
$ pushd icedtea6/openjdk/corba/make/sun/rmi/rmic
$ touch now
$ time /home/sr/staging/staging-build/icedtea6/bootstrap/jdk1.6.0/bin/java
-Xmx896m -Xms128m -XX:PermSize=32m -XX:MaxPermSize=160m
-Xbootclasspath/p:/home/sr/staging/staging-build/icedtea6/openjdk.build/langtools/dist/bootstrap/lib/javac.jar
-jar
/home/sr/staging/staging-build/icedtea6/openjdk.build/langtools/dist/bootstrap/lib/javac.jar
-g -XDignore.symbol.file=true -source 1.5 -target 5 -encoding ascii -classpath
/home/sr/staging/staging-build/icedtea6/bootstrap/jdk1.6.0/lib/tools.jar
-Xprefer:source -sourcepath
/home/sr/staging/staging-build/icedtea6/openjdk.build/corba/gensrc:../../../../src/solaris/classes:../../../../src/share/classes
-d /home/sr/staging/staging-build/icedtea6/openjdk.build/corba/classes
@/home/sr/staging/staging-build/icedtea6/openjdk.build/corba/tmp/sun/sun.rmi.rmic/.classes.list
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

real    0m3.558s
user    0m9.660s
sys     0m0.353s

$ find ../../../../../../openjdk.build/corba/classes -type f -newer now |wc -l
976

Build 2:
$ pushd icedtea6/openjdk/corba/make/sun/rmi/rmic
$ touch now
$ time /home/sr/staging/staging-build/icedtea6/bootstrap/jdk1.6.0/bin/javac
-J-XX:ThreadStackSize=2048 -J-Xmx896m -J-Xms128m -J-XX:PermSize=32m
-J-XX:MaxPermSize=160m -g -XDignore.symbol.file=true -source 1.5 -target 5
-encoding ascii -classpath
/home/sr/staging/staging-build/icedtea6/openjdk.build-ecj/langtools/dist/lib/classes.jar
-Xprefer:source -sourcepath
/home/sr/staging/staging-build/icedtea6/generated.build:../../../../src/share/classes:/home/sr/staging/staging-build/icedtea6/openjdk-ecj/jdk/src/share/classes:/home/sr/staging/staging-build/icedtea6/openjdk-ecj/jdk/src/solaris/classes
-d /home/sr/staging/staging-build/icedtea6/openjdk.build-ecj/corba/classes
@/home/sr/staging/staging-build/icedtea6/openjdk.build-ecj/corba/tmp/sun/sun.rmi.rmic/.classes.list
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

real    0m11.952s
user    0m24.692s
sys     0m1.366s

$ find ../../../../../../openjdk.build-ecj/corba/classes -type f -newer now |wc
-l
6415

Build 3:
$ pushd icedtea6/openjdk/corba/make/sun/rmi/rmic
$ touch now
$ time /home/sr/staging/staging-build/icedtea6/bootstrap/jdk1.6.0/bin/javac
-J-XX:ThreadStackSize=2048 -J-Xmx896m -J-Xms128m -J-XX:PermSize=32m
-J-XX:MaxPermSize=160m -g -XDignore.symbol.file=true -source 1.5 -target 5
-encoding ascii -classpath
/home/sr/staging/staging-build/icedtea6/bootstrap/jdk1.6.0/lib/tools.jar
-bootclasspath
/home/sr/staging/staging-build/icedtea6/bootstrap/jdk1.6.0/jre/lib/rt.jar:/home/sr/staging/staging-build/icedtea6/openjdk.build-ecj/corba/classes
-sourcepath
/home/sr/staging/staging-build/icedtea6/generated:../../../../src/share/classes
-d /home/sr/staging/staging-build/icedtea6/openjdk.build-ecj/corba/classes
@/home/sr/staging/staging-build/icedtea6/openjdk.build-ecj/corba/tmp/sun/sun.rmi.rmic/.classes.list
real    0m4.010s
user    0m3.935s
sys     0m0.082s

$ find ../../../../../../openjdk.build-ecj/corba/classes -type f -newer now |wc
-l
36

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