Re: [rvm-research] Jikes Code Cache Management

Continuing to the previous mail,

if USE_CODE_SPACE is true and the space allocated for the code is full,
then how the jikes rvm replaces the existing code.?

Thanks

Pushparaj

On Sun, May 12, 2013 at 6:23 AM, Pushparaj Motamari
<[email protected]>wrote:

> Hi,
>
> Thank you for your replies, I am looking for space management.
>
> Thank you
>
> Pushparaj
>
> On Thu, May 9, 2013 at 3:40 AM, David P Grove <[email protected]> wrote:
>
>> Michael Bond <[email protected]> wrote on 05/08/2013 04:53:32
>> PM:
>>
>>
>> >
>> > By default, USE_CODE_SPACE is true, and (machine) code is allocated
>> into
>> > special code spaces that are non-moving spaces. However, if
>> > USE_CODE_SPACE is false, then it looks like code is allocated into the
>> > default space, which could be a moving space. Assuming that's right,
>> > then I'm not entirely sure how pointers to code are updated. At least
>> > some calls are indirect: they go through TIBs (virtual dispatch) or the
>> > JTOC (static methods), so just updating these tables is sufficient. Are
>> > all calls indirect, or are there direct calls in the code that need to
>> > be updated by updating pointers in the code itself? I suspect that all
>> > calls are performed indirectly rather than having absolute hard-coded
>> > callee addresses in the code.
>> >
>>
>> Independent of USE_CODE_SPACE, all calls in Jikes RVM are indirect. (even
>> static calls indirect through the JTOC).  On the plus side, this makes
>> adaptive recompilation very simple (install a new version of the code
>> simply by updating a TIB/JTOC pointer).  On the minus side, we are likely
>> losing at least some performance by indirecting on every call.
>>
>> I'd started working on implementing support for direct (pc-relative)
>> calls back at OOPSLA'07 in Montreal, but never completed it.  I still have
>> a patch set kicking around if anyone wants to take another run at it.  I
>> figured it was going to take me a month +/- of solid work to make all the
>> needed changes (pc relative calls on both platforms, still supporting GC of
>> code, adaptive recompilation, etc).
>>
>> --dave
>>
>>
>>
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