Re: Java processors

From:
Lew <lewbloch@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 9 Jul 2012 16:26:42 -0700 (PDT)
Message-ID:
<4669297d-96ef-46aa-ae25-c66986453aaf@googlegroups.com>
Daniele Futtorovic wrote:

Roedy Green allegedly wrote:
Lew wrote, quoted or indirectly quoted someone who said :
&gt;&gt; They don&#39;t do that exactly. There&#39;s no restart.
&gt;&gt;
&gt;&gt; &lt;http://www.oracle.com/technetwork/java/hotspotfaq-138619.html#compiler_warmup&gt;
&gt;
&gt; &quot; HotSpot contains On Stack Replacement technology which will compile
&gt; a running (interpreted) method and replace it while it is still
&gt; running in a loop. No need to waste your applications time warming up
&gt; seemingly infinite (or very long running) loops in order to get better
&gt; application performance.&quot;
&gt;
&gt; It thus stops it is mid flight, possibly half way through a loop,
&gt; writes machine code, creates the equivalent state/register, and picks
&gt; up where it left off (what I ambiguously called restarting) but
&gt; running machine code. I can hardly believe this is possible,
&gt; especially when you think about all the optimisations on the machine
&gt; code.

Sounds to me like you could be misinterpreting that, Roedy. It says
&quot;method... running in a loop&quot;. Not: loop running in a method. I&#39;d rather
interpret that as being about a method running repeatedly in a loop.

Agree with the &quot;walk on water&quot; thing, though.


As cited upthread:
<http://www.oracle.com/technetwork/java/whitepaper-135217.html#optimizations>

Loop unrolling is one of the optimizations mentioned.

--
Lew

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