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

Erik Joelsson erik.joelsson at oracle.com
Tue Oct 4 11:20:17 UTC 2016

New webrev: http://cr.openjdk.java.net/~erikj/8150736/webrev.02/

On 2016-10-04 11:03, Magnus Ihse Bursie wrote:
> On 2016-10-03 10:22, Erik Joelsson wrote:
>> Hello,
>> 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.
> I believe so too. :-) It's great to see this cleared up!
> Overall, I think your patch looks good. A few things:
> * In hotspot/make/GensrcJvmti.gmk, you have added out-commented code. :-)
Created bug JDK-8167078 to track this issue and referred to it in the 
comments, both in GensrcJvmti.gmk and Copy-java.base.gmk. I don't want 
to throw away the build logic for these header files since I believe the 
correct fix is to get the files from hotspot.
> * You have missed updating copyright year overall.
> * I'm wondering a bit about this comment about hotspot, that is now 
> removed:
>     # NOTE: The old build did not strip binaries on macosx.
> As far as I can see, we are now stripping libjvm.dylib. Is this 
> something that has changed, or was the old comment incorrect?
The old comment was correct for the hotspot build, but then the images 
build did a second round of strips. This is how the JDK libraries used 
to get stripped. Since I now let SetupNativeCompilation do the 
stripping, the secondary strip logic is removed and macosx libjvm must 
be stripped like all the others.
> * In jdk/make/Import.gmk, we did a lot of special handling for 
> libjsig, e.g. handle STATIC_BUILD separately, or selecting different 
> versions depending on if client or server was built (which even seemed 
> to be OS dependent). While the old logic looked really suspicios, I'm 
> not sure how to match that to the new code in CompileLibjsig.gmk. Are 
> the end result really the same? If not, can you specify how things 
> have changed and reassure me that it is correct? :-)
Short answer: The end result is the same.

STATIC_BUILD disabled building and importing of libjsig and still does.

What the old logic basically did was creating symlinks from each variant 
subdir like this:

lib/amd64/server/libjsig.so -> ../libjsig.so

For the library that was trivial, but it also did the same for the 
symbol files, and zipped the link if zipping symbols. On macosx, with 
the dSYM dirs, this got even more complicated, which is the reason for 
platform checks (as well as libjsig not being built on windows).

The only difference is this. When --with-native-debug-symbols=zipped is 
set, we end up with both zipped and non zipped debug symbols in the 
modules_libs/<module> dir. Because of this, both the zipped and non 
zipped symlink are created, where before, only the zipped one would be.
>>> 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.
> I agree that product-images-jdk is not a very good name. But I also 
> agree with Erik's reasoning. :-) However, I have a suggestion that I 
> think will suit you both. :)
> I suggest that we call the new, fine-grained, targets "jdk-image", 
> "jre-image" and "symbols-image". This is in line with the singular 
> form of "docs-image" and "test-image". The actual reason that "images" 
> (and hence, "product-images") was using the plural form was that it 
> consisted of these several individual images. So, if we have:
> # Define product images
> product-images: jdk-image jre-image symbols-image
> # Add a common alias
> images: product-images
> In fact, we almost already does something like this:
> # This target builds the product images, e.g. the JRE and JDK image
> # (and possibly other, more specific versions)
> product-images: product-images-jdk product-images-jre 
> product-images-symbols \
>     zip-security exploded-image
This is so simple and obvious, fixed.
> ... which got me wondering if "zip-security" is actually correctly 
> placed. I assume it should be a dependency to product-images-jdk (or 
> rather "jdk-image" :)), instead.
zip-security is a bit of an oddity. Right now is not a good time to sort 
it out however. I have other work in progress where it will be. Added a 
comment about it.

> /Magnus
>> /Erik
>>> 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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