Stop using precompiled headers for Linux?

[Aleksey Shipilev]

On 11/02/2018 12:14 PM, Magnus Ihse Bursie wrote:
> And here is the "winning" list (which I declared as "on or above 130, without inline"). I encourage
> everyone to try this on their own system, and report back the results!
> 
> #ifndef DONT_USE_PRECOMPILED_HEADER
> # include "classfile/classLoaderData.hpp"
> # include "classfile/javaClasses.hpp"
> # include "classfile/systemDictionary.hpp"
> # include "gc/shared/collectedHeap.hpp"
> # include "gc/shared/gcCause.hpp"
> # include "logging/log.hpp"
> # include "memory/allocation.hpp"
> # include "memory/iterator.hpp"
> # include "memory/memRegion.hpp"
> # include "memory/resourceArea.hpp"
> # include "memory/universe.hpp"
> # include "oops/instanceKlass.hpp"
> # include "oops/klass.hpp"
> # include "oops/method.hpp"
> # include "oops/objArrayKlass.hpp"
> # include "oops/objArrayOop.hpp"
> # include "oops/oop.hpp"
> # include "oops/oopsHierarchy.hpp"
> # include "runtime/atomic.hpp"
> # include "runtime/globals.hpp"
> # include "runtime/handles.hpp"
> # include "runtime/mutex.hpp"
> # include "runtime/orderAccess.hpp"
> # include "runtime/os.hpp"
> # include "runtime/thread.hpp"
> # include "runtime/timer.hpp"
> # include "services/memTracker.hpp"
> # include "utilities/align.hpp"
> # include "utilities/bitMap.hpp"
> # include "utilities/copy.hpp"
> # include "utilities/debug.hpp"
> # include "utilities/exceptions.hpp"
> # include "utilities/globalDefinitions.hpp"
> # include "utilities/growableArray.hpp"
> # include "utilities/macros.hpp"
> # include "utilities/ostream.hpp"
> # include "utilities/ticks.hpp"
> #endif // !DONT_USE_PRECOMPILED_HEADER

"make clean hotspot" times on my TR 2950X Linux x86_64 build node:

 no PCH: {134s, 135s, 135s} wall, ~59m user
old PCH: {136s, 136s, 135s} wall, ~55m user
new PCH: {111s, 108s, 108s} wall, ~45m user

I am all for shallower PCH, even knowing I would disable it for my builds anyway :)

Thanks,
-Aleksey