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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">Hi Michihiro,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">thanks for posting the new webrev. I think this looks much better, now.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">I don’t like the “if log_is_enabled() acquire()” code so much, but it looks correct to me. I’d prefer your OrderAccess:consume() proposal,
but I can live with it if other reviewers prefer it.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">I couldn’t find any store-load pattern which may miss ordering, but I’d highly appreciate if another reviewer double-checked that the
barriers are right this time.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">If needed, we could use memory_order_acq_rel which I’m planning to add with JDK-8202080. I guess this wouldn’t really impact performance.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">I think 6% performance gain is really worth doing this change.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">Best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">Martin<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Michihiro Horie [mailto:HORIE@jp.ibm.com]
<br>
<b>Sent:</b> Montag, 23. April 2018 12:34<br>
<b>To:</b> ppc-aix-port-dev@openjdk.java.net; hotspot-dev@openjdk.java.net; hotspot-gc-dev@openjdk.java.net<br>
<b>Cc:</b> Hiroshi H Horii <HORII@jp.ibm.com>; Gustavo Romero <gromero@linux.vnet.ibm.com>; Kazunori Ogata <OGATAK@jp.ibm.com>; shade@redhat.com; aph@redhat.com; Doerr, Martin <martin.doerr@sap.com><br>
<b>Subject:</b> RFR(M): 8154736: enhancement of cmpxchg and copy_to_survivor for ppc64<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p><span lang="EN-US" style="font-size:10.0pt">Dear all,</span><span lang="EN-US"><br>
<br>
</span><span lang="EN-US" style="font-size:10.0pt">I would like to ask reviews on 8154736 “enhancement of cmpxchg and copy_to_survivor”. The change adds options to avoid expensive syncs with compare-and-exchange. An experiment by using SPECjbb2015 showed 6%
improvement in critical-jOPS. This change focuses on ppc64 but would be potentially beneficial for aarch64.</span><span lang="EN-US"><br>
<br>
</span><span lang="EN-US" style="font-size:10.0pt">Although discussions stopped at
</span><a href="http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2016-October/002718.html"><span lang="EN-US" style="font-size:10.0pt">http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2016-October/002718.html</span></a><span lang="EN-US" style="font-size:10.0pt">,
I would like to restart the review by taking over Hiroshi's work if the discussion is still open.</span><span lang="EN-US"><br>
<br>
</span><span lang="EN-US" style="font-size:10.0pt">Bug: </span><a href="https://bugs.openjdk.java.net/browse/JDK-8154736"><span lang="EN-US" style="font-size:10.0pt">https://bugs.openjdk.java.net/browse/JDK-8154736</span></a><span lang="EN-US"><br>
</span><span lang="EN-US" style="font-size:10.0pt">Webrev: </span><a href="http://cr.openjdk.java.net/~mhorie/8154736/webrev.08/"><span lang="EN-US" style="font-size:10.0pt">http://cr.openjdk.java.net/~mhorie/8154736/webrev.08/</span></a><span lang="EN-US"><br>
<br>
</span><span lang="EN-US" style="font-size:10.0pt">Previous review had discussions on improper log output (</span><a href="http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2016-September/002672.html"><span lang="EN-US" style="font-size:10.0pt">http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2016-September/002672.html</span></a><span lang="EN-US" style="font-size:10.0pt">).
Logs can be generated properly with this change, but I would like to ask if we should use “if(log) OrderAccess:acquire()” as is in webrev or more general approach with a call to OrderAccess:consume() with empty implementation on all supported platforms.</span><span lang="EN-US"><br>
<br>
</span><span lang="EN-US" style="font-size:10.0pt">Also, there were discussions on the problem of unawareness of copied obj (</span><a href="http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2016-October/002696.html"><span lang="EN-US" style="font-size:10.0pt">http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2016-October/002696.html</span></a><span lang="EN-US" style="font-size:10.0pt">).
This change adds “release” in cmpxchg_pre_membar. This was discussed in </span><a href="http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2016-October/002698.html"><span lang="EN-US" style="font-size:10.0pt">http://mail.openjdk.java.net/pipermail/ppc-aix-port-dev/2016-October/002698.html</span></a><span lang="EN-US" style="font-size:10.0pt">.</span><span lang="EN-US"><br>
<br>
</span><span lang="EN-US" style="font-size:10.0pt">I measured SPECjbb2015 with its multi JVMs mode on a POWER8 node (for JDK11, I modified MANIFEST in specjbb2015.jar to specify locations of JAXB related libraries). As a result, critical-jOPS improved by 6%
due to this change.</span><span lang="EN-US"><br>
<br>
</span><span style="font-size:10.0pt">Best regards,</span><br>
<span style="font-size:10.0pt">--</span><br>
<span style="font-size:10.0pt">Michihiro,</span><br>
<span style="font-size:10.0pt">IBM Research - Tokyo</span><o:p></o:p></p>
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