Thanks, Erik. Very nice answer!
So it seems there are two ways to determine whether a method is hot or not: one is sampling-based, the other is (invocation) counter-based.
The former prefers methods with longer accumulated execution time, while the later prefers methods with more invocations so far, right?

May I have a further question?

I tested the command line arguments you suggested: "-X:aos:printOptions", 
from which I found two interesting options as below:

method_sample_size             = 3
counter_based_sample_interval  = 1000

It seems the first one is the threshold (# of samples a method got) to determine a method is "hot" or not,
and the second one is the sampling rate (in the default setting, it is taking 1 sample every 1000 msecs). 

Is my understanding correct?

I observed the changing of method_sample_size affects the # of methods opt-compiled. 
However, I did not see counter_based_sample_interval affect the  # of methods opt-compiled at all.
Did I miss anything?

Thanks again!


On Thu, Nov 7, 2013 at 4:13 AM, Erik Brangs <> wrote:

On 07.11.2013 00:04, Zhijia Zhao wrote:
> I tried to test the effects of "invocation_count_threshold" with the following command.
> rvm -X:vm:measureCompilation=true -X:aos:invocation_count_threshold=1 -jar dacapo-2006-10-MR2.jar -s small eclipse

Invocation counters are disabled by default. You will need to enable them first by adding "-X:base:invocation_counters=true" as a command line argument. You will need to fix bugs if you want to use invocation counters (see

To see the default values of command line arguments for AOS or the baseline compiler, use "rvm -X:aos:printOptions" and "rvm -X:base:printOptions" respectively.

Kind regards,

Erik Brangs

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Zhijia Zhao
PhD Student
Computer Science Dept., The College of William & Mary, USA