On 10/09/2012 15:00, Magnus Ihse Bursie wrote:
In the new build system, fast incremental builds of Java code is
dependent on the new "smart javac", which unfortunately has still not
proven stable enough to be enabled by default, even in the
experimental build-infra forest. It is still our hope that it will
turn out to be good enough to be used as default, but I don't want to
trust hope alone.
As an interim solution, I have just created the following two
shortcuts. Both of these bypass the proper dependency detection. This
means that make will cut to the chase and recompile faster, but it
also means that you need to take over the responsibility of making
sure dependencies are correct. This is very similar to the "*-only"
(e.g. hotspot-only) targets that are current available in the new
build system.
First shortcut is to skip parts of the JDK makefile. By typing e.g.
"make jdk JDK_TARGET=classes", the JDK build will stop after building
the "classes" target (which compiles the majority of the JDK java
files). An even faster, but less safe, version is "make jdk-only
JDK_TARGET=classes-only", which will jump directly to the JDK
Makefile, and only execute the "classes" target. In this way,
absolutely no time is spent before starting to compile Java classes.
Second shortcut is to limit the classes that are recompiled by the JDK
"classes" target. Currently, *all* (more or less) Java classes in the
JDK is recompiled at once. While this speeds up things considerably at
a first time compilation, it makes all subsequent builds take the same
time. By specifying e.g. JDK_FILTER=java/nio, only files in the
java/nio package will get compiled. This is, I think, similar (but not
strictly not identical) to the effect of "sub-directory builds". It is
possible to use an even more fine-grained filter, separated by comma,
e.g. JDK_FILTER=java/nio/channels,java/nio/charset -- the smaller
number of Java files your filter includes, the faster the build will
go (more or less).
These two can of course be combined.
I would like to point out that this is hopefully a temporary solution
-- if proper dependency checking and incremental builds get fast
enough, this kind of trickery should not be needed. If this happens,
we will remove the support for these shortcuts since they do carry a
risk of improper builds.
/Magnus
I can't give you any feedback on this temporary solution without trying
it (this isn't build-infra yet, right?).
So far my experience is that touching native code and re-building is
super fast, it's on par to executing specific make files in the old
build (while wearing the appropriate amulet around one's neck of
course). Touching java classes and re-building takes a long time,
sometimes 1.5-2 minutes for me, so quite a bit slower than running
specific make files.
-Alan
