RFR (S) 8147978: Remove Method::_method_data for C1
david.holmes at oracle.com
Fri Feb 5 03:10:19 UTC 2016
On 5/02/2016 12:10 PM, Chris Plummer wrote:
> Hi David,
> On 2/4/16 5:43 PM, David Holmes wrote:
>> Hi Chris,
>> On 4/02/2016 5:20 PM, Chris Plummer wrote:
>>> Please review the following for removing Method::_method_data when only
>>> supporting C1 (or more specifically, when not supporting C2 or JVMCI).
>> Does JVMCI exist with C1 only?
> My understanding is it can exists with C2 or on its own, but currently
> is not included with C1 builds.
>> The COMPILER2_OR_JVMCI conjunction makes things a bit messy. Can we
>> abstract that behind a single variable, INCLUDE_METHOD_DATA (or some
>> such) to make it cleaner?
> I'll also be using COMPILER2_OR_JVMCI with another change to that
> removes some MethodCounter fields. So yes, I can add
> INCLUDE_METHOD_DATA, but then will need another INCLUDE_XXX for the
> MethodCounter fields I'll be conditionally removing.
Okay. It is ugly though :(
>>> This will help reduce dynamic footprint usage for the minimal VM.
>>> As part of this fix, ProfileInterperter is forced to false unless C2 or
>>> JVMCI is supported. This was mainly done to avoid crashes if it is
>>> turned on and Method::_method_data has been excluded, but also because
>>> it is not useful except to C2 or JVMCI.
>> Are you saying that the information generated by ProfileInterpreter is
>> only used by C2 and JVMCI? If that is case it should really have been
>> a C2 only flag.
> That is my understanding. Coleen confirmed it for me. I believe she got
> her info from the compiler team. BTW, we need a mechanism to make these
> conditionally unsupported flags a constant value when they are not
> supported. It would help deadstrip code.
Does it work to define it only in c2_globals.hpp and jvmci_globals.hpp,
then in the shared globals.hpp define the flag as a constant "false" if
not C2 or JVMCI? (I admit the multiple layers of macros makes it hard to
see exactly how to make such a declaration.)
>> If ProfileInterpreter is forced to false then shouldn't you also be
>> checking TraceProfileInterpreter and PrintMethodData use as well
> Yes, I can add those.
Thinking more on this, forcing ProfileInterpreter off doesn't really
change anything, so I don't think you need to validate these flags are
>>> Webrev: http://cr.openjdk.java.net/~cjplummer/8147978/webrev.02/
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8147978
>>> Test with JPRT -testset hotspot.
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