Hi Peter, Thank you for your comment. I thought the compiler must insert memory fence at the end of object initializer, but I agree relying on it is not correct w.r.t. JMM.
Then I'll take 1) 1) Put VarHandle.fullFence() between initialization of ClassDataSlot[] and writing the reference to non-volatile dataLayout. (Webrev: http://cr.openjdk.java.net/~horii/8187033/webrev.01-fence/), as it achieved the best performance. Regards, Ogata Peter Levart <peter.lev...@gmail.com> wrote on 2017/09/04 17:06:21: > From: Peter Levart <peter.lev...@gmail.com> > To: Kazunori Ogata <oga...@jp.ibm.com>, core-libs-dev <core-libs- > d...@openjdk.java.net>, Aleksey Shipilev <sh...@redhat.com>, Hans Boehm > <hbo...@google.com> > Date: 2017/09/04 17:06 > Subject: Re: RFR: 8187033: [PPC] Imporve performance of > ObjectStreamClass.getClassDataLayout() > > Hi Ogata, > On 09/04/2017 07:20 AM, Kazunori Ogata wrote: > 4) Put reference to ClassDataSlot[] into a final field of an object, read > the final field immediately after the object creation, and store it to > non-volatile dataLayout. I think this is also correct based on the > semantics of final fields and data dependency. > Webrev: http://cr.openjdk.java.net/~horii/8187033/webrev.01-final2/ > > I'm sure others will tell you that final field semantics only works across > threads when you also read the final field in the other thread from the > thread that writes to it. Storing and reading the final field in the same > thread won't help order the write to a non final field after writes that > precede it in program order nor to order the read of a non-final field in > the other thread before reads that follow it in program order. > > Regards, Peter
