<br><br><div class="gmail_quote">On Fri, May 4, 2012 at 8:48 AM, Xin Tong <span dir="ltr"><<a href="mailto:xerox.time.tech@gmail.com" target="_blank">xerox.time.tech@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On Thu, May 3, 2012 at 8:45 PM, Xin Tong <<a href="mailto:xerox.time.tech@gmail.com">xerox.time.tech@gmail.com</a>> wrote:<br>
> On Thu, May 3, 2012 at 8:29 PM, Krystal Mok <<a href="mailto:rednaxelafx@gmail.com">rednaxelafx@gmail.com</a>> wrote:<br>
>> On 2012-5-4, at 8:16, Xin Tong <<a href="mailto:xerox.time.tech@gmail.com">xerox.time.tech@gmail.com</a>> wrote:<br>
>><br>
>>> i would like to know how to debug in hotspot, what are some of the<br>
>>> standard procedures ? Lets say, the hotspot fails to run a Java<br>
>>> program. a few steps to triage the problem.<br>
>>><br>
>>> 1. disable JIT compilers. hotspot has 2 compilers c1 and c2. they are<br>
>>> both used if TieredCompilation is enabled. How do I disable both of<br>
>>> them.<br>
>><br>
>> It's there in the globals.hpp file: -XX:-UseCompiler<br></div></blockquote><div><br></div><div>I forgot to mention there's a shorter (and better supported) equivalent to this: -Xint</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">
>><br>
>>> 2. if the Java program passes after the JIT is disabled. There is a<br>
>>> good chance that the problem is cause by the JIT. I want to narrow<br>
>>> down to a specific method, I can use PrintCompilation to find out all<br>
>>> the method compiled, but how can I disable one specific method from<br>
>>> being compiled.<br>
>><br>
>> -XX:CompileCommand='exclude,your/class,yourMethod'<br>
>> Or an equivalent .hotspot_compiler configuration file.<br>
>> Read this thread for example (in Chinese): <a href="http://hllvm.group.iteye.com/group/topic/28201" target="_blank">http://hllvm.group.iteye.com/group/topic/28201</a><br>
<br>
</div>By the way, one thing we can do here is to force c1 to compile a<br>
method. i.e. c2 is more likely to fail than c1 as it does more<br>
optimizations. how do i force c1 to compile a method ?</blockquote><div><br></div><div>What platform and version of JDK are you using?</div><div>If there's a Client VM for your platform, use that;</div><div>If you're using JDK7 or JDK8, try -XX:+TieredCompilation -XX:TieredStopAtLevel=1, which effectively disables C2 in tiered mode.</div>
<div>Otherwise, if you have to use the Server VM (for instance, on amd64 where Oracle doesn't provide a Client VM build), and you're using an old version of JDK6, I'm not sure if there's a way to force compilation with C1.</div>
<div>And, there's no way (yet) to force compilation with C1/C2 on a per-method granularity.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">and how do i<br>
know which compiler is used to compile a method in the<br>
PrintCompilation log or through any other options ?<br></blockquote><div><br></div><div>Please refer to this note: <a href="https://gist.github.com/1165804#file_notes.md">https://gist.github.com/1165804#file_notes.md</a></div>
<div>I was supposed to put this up in the HotSpotInternals wiki, but somehow I haven't done it yet...oops.</div><div><br></div><div>- Kris</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="HOEnZb"><div class="h5"><br>
>><br>
>>> 3. if i am able to limit down to a specific method, i want to start<br>
>>> disabling optimizations, is there an option to disable all<br>
>>> optimizations in the c1 and c2 compilers, or i need to do it manually<br>
>>> ?<br>
>>><br>
>><br>
>> I don't think there's an all-in-one flag to turn all optimizations off. At least not for now.<br>
>> See c1_globals.hpp and c2_globals.hpp to get an idea of what optimizations you can turn off.<br>
>><br>
>> - Kris<br>
>><br>
>>> Thanks<br>
><br>
> Thank you very much Kris. This is very helpful.<br>
</div></div></blockquote></div><br>