RFR 8194085: Obsolete the deprecated SafepointSynchronize flags and remove related code

[Daniel D. Daugherty]

On 2/21/18 1:31 PM, harold seigel wrote:
> Hi,
>
> Please review this JDK-11 change to obsolete the 
> SafepointSpinBeforeYield, DeferThrSuspendLoopCount, and 
> DeferPollingPageLoopCount options and related code.  With this change, 
> these options are still accepted on the command line but have no 
> affect other than to generate these warning messages:
>
>    Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option
>    SafepointSpinBeforeYield; support was removed in 11.0
>    Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option
>    DeferThrSuspendLoopCount; support was removed in 11.0
>    Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option
>    DeferPollingPageLoopCount; support was removed in 11.0
>
> Open Webrev: 
> http://cr.openjdk.java.net/~hseigel/bug_8194085/webrev/index.html

src/hotspot/share/runtime/globals.hpp
     No comments.

src/hotspot/share/runtime/safepoint.hpp
     L110 - Any particular reason for adding the extra blank line?

src/hotspot/share/runtime/safepoint.cpp
     L81: int SafepointSynchronize::_defer_thr_suspend_loop_count = 4000;

         In safepoint.hpp:

             L211:   static void set_throughput_mode() {
             L212:     _defer_thr_suspend_loop_count = 1;

         And in arguments.cpp:

             L2947:     } else if (match_option(option, "-Xconcurrentio")) {
             L2954: SafepointSynchronize::set_throughput_mode();

         So before we had the ability to tune the DeferThrSuspendLoopCount
         value when the "-Xconcurrentio" option was specified. Now we use
         the setting of "1" when the "-Xconcurrentio" option is specified
         with no way to override that value. Okay.

         So in this bug:

             8191327 Deprecate DeferThrSuspendLoopCount

         the option was deprecated, but there's no real explanation for
         why this is okay. I understand the need to simplify the safepoint
         code, but there isn't any rationale for why this won't impact
         customers other than the fact that this option has been
         advertised as:

             product(intx, DeferThrSuspendLoopCount,     4000, \
                     "(Unstable, Deprecated) "

         Okay, I'm done mulling here. Since I've never heard of the
         "-Xconcurrentio" option before today, I'm not going to stress
         over the tuneablity of an unstable option when -Xconcurrentio"
         is used.

src/hotspot/share/runtime/arguments.cpp
     No further comments.

Thumbs up!

Dan


>
> JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8194085
>
> The change was tested with Mach5 tiers 1 and 2 on all Mach5 platforms 
> and tiers 3-5 in Linux-X64.
>
> Thanks, Harold