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!

Zhijia













On Thu, Nov 7, 2013 at 4:13 AM, Erik Brangs <erik.brangs@gmx.de> wrote:
Hi,

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 http://jira.codehaus.org/browse/RVM-919).

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
web: http://www.cs.wm.edu/caps/zzhao