How to change compilation policy to trigger C2 compilation ASAP?

[Vladimir Kozlov]

I had said "if don't need profiling or inlining" :)

Of cause low threashold affects quality of generated code. Especially if 
it has branches and calls. And you should not expect that you will get 
the same inlining. So profiling result of such code should be considered 
only as approximation.

Vladimir

On 5/19/15 6:15 PM, Vitaly Davidovich wrote:
> Vladimir,
>
> Is 100 actually generally good/decent based on our conversation from the
> other day regarding lack of scaling down certain inlining thresholds?
>
> Thanks
>
> sent from my phone
>
> On May 19, 2015 9:12 PM, "Vladimir Kozlov" <vladimir.kozlov at oracle.com
> <mailto:vladimir.kozlov at oracle.com>> wrote:
>
>     If you want only C2 compilation you can disable tiered compilation
>     (since you don't want to spend to much on profiling anyway) and set
>     low CompileThreshold (you need only this one for non-tiered compile):
>
>     -XX:-TieredCompilation -XX:CompileThreshold=100
>
>     If your method is simple and don't need profiling or inlining the
>     generated code could be same quality as with long profiling.
>
>     An other approach is to set threshold per method (scale all
>     threasholds (C1, C2, interpreter) by this value). For example to
>     reduce thresholds by half:
>
>     -XX:CompileCommand=option,SomeClass.someMethod,double,CompileThresholdScaling,0.5
>
>     Vladimir
>
>     On 5/19/15 5:43 PM, Tangwei (Euler) wrote:
>
>         My goal is just to reach peak performance quickly. Following is
>         one tier
>         threshold combination I tried:
>
>         -XX:Tier0ProfilingStartPercentage=0
>
>         -XX:Tier3InvocationThreshold=3
>
>         -XX:Tier3MinInvocationThreshold=2
>
>         -XX:Tier3CompileThreshold=2
>
>         -XX:Tier4InvocationThreshold=4
>
>         -XX:Tier4MinInvocationThreshold=3
>
>         -XX:Tier4CompileThreshold=2
>
>         Regards!
>
>         wei
>
>         *From:*Vitaly Davidovich [mailto:vitalyd at gmail.com
>         <mailto:vitalyd at gmail.com>]
>         *Sent:* Tuesday, May 19, 2015 9:33 PM
>         *To:* Tangwei (Euler)
>         *Cc:* hotspot compiler
>         *Subject:* Re: How to change compilation policy to trigger C2
>         compilation ASAP?
>
>         Is your goal specifically to have C2 compile or just to reach peak
>         performance quickly? It sounds like the latter.  What values did you
>         specify for the tier thresholds? Also, it may help you to
>         -XX:+PrintCompilation to tune the flags as this will show you which
>         methods are being compiled, when, and at what tier.
>
>         sent from my phone
>
>         On May 19, 2015 9:01 AM, "Tangwei (Euler)" <tangwei6 at huawei.com
>         <mailto:tangwei6 at huawei.com>
>         <mailto:tangwei6 at huawei.com <mailto:tangwei6 at huawei.com>>> wrote:
>
>         Hi All,
>
>             I want to run a JAVA application on a performance simulator,
>         and do a
>         profiling on a hot function JITTed with C2 compiler.
>
>         In order to make C2 compiler compile hot function as early as
>         possible,
>         I hope to reduce the threshold of function invocation
>
>         count in interpreter and C1 to drive the JIT compiler
>         transitioned to
>         Level 4 (C2) ASAP. Following is the option list I try, but
>
>         failed to find a right combination to meet my requirement.
>         Anyone can
>         help to figure out what options I can use?
>
>         Thanks in advance.
>
>         -XX:Tier0ProfilingStartPercentage=0
>
>         -XX:Tier3InvocationThreshold
>
>         -XX:Tier3MinInvocationThreshold
>
>         -XX:Tier3CompileThreshold
>
>         -XX:Tier4InvocationThreshold
>
>         -XX:CompileThreshold
>
>         -XX:Tier4MinInvocationThreshold
>
>         -XX:Tier4CompileThreshold
>
>         Regards!
>
>         wei
>