Re: [rvm-research] How to record objects' read/write times

Hi, Eliot


On Mon, May 11, 2015 at 7:58 PM, Eliot Moss <[email protected]> wrote:
> On 5/11/2015 3:53 AM, 王晨曦 wrote:
>
>>    I want to record objects' read and write times.
>
> 1) What do you mean by "times"?  Given the heavy weight of such instrumentation,
>     wall clock time would not be very meaningful.  If you want counts, or the
>     sequence of accesses to fields, then a modified version of ElephantTracks
>     may be useful to you.


  I'm sorry for my poor English. I want to use the Write Barrier to
count  how many times the elements of the object are load/store.


>
> 2) Collecting such detailed information is fraught with a number of difficulties.
>     Benchmarks can time out, etc.
>
> 3) In a system like Jikes RVM, you have to be very careful not to instrument
>     certain parts of the system, such as the garbage collector, and whatever
>     part of the system gets invoked by your instrumentation (otherwise you get
>     infinite recursion).
>
> 4) Some deeply integral parts of at least some systems do not tolerate well
>     certain kinds of instrumentation.  See the ElephantTracks paper for some
>     discussion of doing this from the bytecode level; doing it in the JikesRVM
>     compiler may get around some of those issues, but not all.
>
> 5) Existing tools available in Eclipse, that use the JVM Tool Interface (jvmti),
>     may do what you're looking for.

I'm not dong an offline profiling job. I want to use this information
to optimize the JikesRVM's runtime. So, I want to modify the Write
Barrier and ask some details about the Write Barrier.

Thank you for your help!

>
> As we try to explain to people posing queries like this, tell us more about what
> you're really trying to accomplish, and we can probably be more helpful.  There
> may be better strategies to get at what it is you *really* want :-) ...
>
> Eliot Moss
>
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-- 
ChenXi.Wang
ICT.CAS China

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