RFR: JDK-8150736: Excessive disk space used by build system

Erik Joelsson erik.joelsson at oracle.com
Mon Oct 3 08:22:26 UTC 2016


On 2016-10-01 14:13, David Holmes wrote:
> Hi Erik,
> This is a big change that is hard to digest. I assume the actual 
> images themselves are unaffected by this change?
I understand that and I have been working on this for some time in the 
background. Yes, I have done quite extensive comparisons during this 
work so there should not be any relevant differences in the images. 
There are some, for example jexec and jspawnhelper are now stripped 
while the old strip logic missed them. I consider that fixing a bug.

I was about to leave this patch for another release but since the 
schedule was moved, and Magnus is available to review things again, I 
thought it was worth trying to get it in. I believe it will add 
significant value.
> An initial nit - why use "product-" in the target names? "images-jdk" 
> etc seems perfectly sufficient, and "product" may be a misnomer.
A while back when we started introducing other images (test-image, 
docs-image, symbols-image) we also renamed the old images target to 
product-images. We left the alias images though since it's fairly well 
established, and introduced the all-images target to build all of them. 
To me it was then natural to create sub targets of product-images rather 
than images for jdk and jre. I do think the new targets are too long 
however and because of that will likely not see much use. Perhaps we can 
add aliases for them too as you suggest.

> Thanks,
> David
> On 30/09/2016 8:17 PM, Erik Joelsson wrote:
>> Here is a rather large patch which should make life better for most
>> people building and developing OpenJDK. The main goal of this patch is
>> to reduce unnecessary space used by the build. A side goal also become
>> to figure out a better general strategy for handling native debug info
>> during the build since that was a large part of the wasted space. These
>> are the high level changes:
>> 1. Removed the dist step in the hotspot build (and the corresponding
>>    import step in the jdk build) and linking libjvm directly into
>>    support/modules_libs. This removes 2 extra copies of all the hotspot
>>    native libraries.
>> 2. Made many files in the exploded image ($(OUTPUT_DIR)/jdk) symlinks
>>    into support/modules_*. Note that binaries and libraries cannot be
>>    symlinks since the image won't run then. Debug symbols and other
>>    files seem to work fine though.
>> 3. Introduced separate top level targets for building the jdk, jre (and
>>    serverjre) images. A developer can run "make product-images-jdk" and
>>    skip the others. The test targets now depend on just the jdk image
>>    to avoid building extra images that aren't needed for tests.
>> 4. Changed SetupNativeCompilation to strip binaries by default unless
>>    told not to, and removed the separate strip build step. This lets us
>>    get rid of modules_*-stripped.
>> 5. Build debug symbols into the OUTPUT_DIR in SetupNativeCompilation
>>    (instead of OBJECT_DIR and then copy to OUTPUT_DIR). For normal jdk
>>    and hotspot libraries, this means the debug symbols end up directly
>>    in support/modules_libs/$MODULE/... and there is only one copy of 
>> them.
>> 6. If zipping debug symbols, this will also leave the unzipped
>>    debugsymbols in OUTPUT_DIR, where we wouldn't do so before. This
>>    also means that the exploded image will get symlinks to the unzipped
>>    debug symbols regardless of if we are asked to zip them or not. This
>>    in turn means that debugging the exploded image will just work. This
>>    change is space neutral since we were already keeping a copy of the
>>    unzipped debugsymbols in the OBJECT_DIR before, they have just been
>>    moved to a more useful place.
>> 7. Stop copying debug symbols from test native binaries since we aren't
>>    stripping them anyway. Better to just leave debug information in the
>>    test binaries.
>> The reduction in size of course varies a lot depending on OS and
>> configuration, but as an example, on my 64bit Linux workstation
>> (debug-symbols=zipped) the size of the build directory has gone from
>> 5.8GB when building "make images" before to 3.8GB when building "make
>> product-images-jdk". The biggest gain is from only building the jdk
>> image when only that is needed. A fairer comparison is "make images
>> test-image" which has gone from 7.3GB to 5.4GB, much due to not
>> duplicating debug information in test binaries. On Solaris the gain is
>> generally bigger.
>> Another nice effect of this is that the exploded image now has debug
>> information for all native libraries by default, and that handling of
>> dSYM directories on Macosx should now work properly.
>> The only significant changes detected by comparison builds is that some
>> binaries that previously weren't stripped, now are, which they also
>> should be.
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8150736
>> Webrev: http://cr.openjdk.java.net/~erikj/8150736/webrev.01/
>> /Erik

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