RFR: JDK-8146403: Windows build can be faster

[Magnus Ihse Bursie]

Hi,

In InitSupport.gmk, please restore the comment:
  # Only do this if make has not been restarted, and if we do not force it.

In jdk/make/gensrc/GensrcExceptions.gmk:
The old construct resulted in the output "Generating exceptions classes" 
(but a bit irregularly), could you please re-add it as a LogInfo?

In make/CompileTools.gmk, the copyright header says 2014, which is at 
least one year too early. :-) (In fact, all modified files should really 
get bumped to 2016).

Apart from this, it looks good to me.

/Magnus

On 2016-01-05 11:58, Erik Joelsson wrote:
> Hello,
>
> During the hotspot makefile conversion, we have been reminded of 
> inefficiencies when running make in Cygwin. We still have a pretty 
> severe performance regression in the new hotspot build compared to the 
> old on Windows in certain situations, my laptop being one such 
> situation. A recent comparison there between just the old and new 
> hotspot build:
>
> release new 00:04:30
> release old 00:03:10
> fastdebug new 00:04:59
> fastdebug old 00:03:37
>
> Much of the extra time is spent spawning various shell processes for 
> book keeping, like saving failure logs, creating header dependency 
> files etc.
>
> It also takes a very long time to do a "do nothing" rebuild when 
> nothing has changed. On my laptop, repeating "make jimages" often 
> takes as long as 40 seconds to figure out that nothing needs to be 
> rebuilt. In this case there are several culprits.
>
> I have been working on improvements in these areas to reduce the 
> overhead. The "do nothing" rebuild of jimages is down to around 25 
> seconds. A full images build is around 1-2 minutes faster from 24 to 
> 22 minutes, but fluctuates quite a bit. The new hotspot build is also 
> improved:
>
> release: 3:44
> fastdebug: 4:02
>
> Here is a list of the kinds of changes I've made:
>
> * Rewrote logger.sh to use a different construct. It drastically 
> reduces the number of bash processes being spawned. Basically you can 
> pipe like this: "> >(tee logfile) 2> >(tee logfile >&2)". I also 
> managed to reduce the extra sed/grep commands needed for the header 
> dependencies even more. A side effect of this is that the log files 
> for each native compilation unit are always saved instead of being 
> deleted on successful compilation. I see no issue with this.
>
> * Changed all recipes that contain echo for logging to instead use new 
> LogInfo macro, which in turn calls $(info ) if appropriate.
>
> * Changed all recipes that contain mkdir to instead use MakeDir macro, 
> which only executes mkdir if the directory doesn't exist.
>
> * In HotspotWrapper.gmk there is an optimization to avoid calling the 
> hotspot makefiles at all if nothing has changed. This runs a find over 
> the whole hotspot repository. I reduced this to only run over src and 
> make sub dirs to avoid the pretty large test dir (since test/closed 
> has grown quite a bit).
>
> * Split Tools.gmk into CompileTools.gmk and Tools.gmk, to avoid having 
> the buildtools compilation being reevaluated by all makefiles needing 
> the tools definitions.
>
> * Split Modules.gmk to avoid having the module deps generation being 
> reevaluated multiple times. Made the new GenerateModuleDeps.gmk an 
> explicit call from Init.gmk.
>
> Since these improvements affect much more than just the new hotspot 
> build, I intend to push this to JDK 9 directly.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8146403
> Webrev: http://cr.openjdk.java.net/~erikj/8146403/webrev.01/
>
> /Erik