code review 10139043: runtime: use persistentalloc instead of mallocgc for itab

runtime: use persistentalloc instead of mallocgc for itab
Reduces heap size.

[dvyukov, 2013-06-09 17:21:08]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://dvyukov%40google.com@code.google.com/p/go/

[remyoudompheng, 2013-06-09 17:28:32]

What is the order of magnitude of the savings (number of objects, size in bytes)
?

[dvyukov, 2013-06-09 17:36:52]

On 2013/06/09 17:28:32, remyoudompheng wrote:
> What is the order of magnitude of the savings (number of objects, size in
bytes)
> ?

I am sure the savings are small (the number of interface implementations).
But aside from increasing load on GC, they also pin MSpan's in memory. I.e. if a
MSpan is unlucky to hold 1 such object, the span will never reused or returned
to OS.
And on top of that, I think it's just the right way to do it -- allocate
persistent objects with persistentalloc.

[bradfitz, 2013-06-09 17:51:20]

LGTM



On Sun, Jun 9, 2013 at 7:36 PM, <dvyukov@google.com> wrote:

> On 2013/06/09 17:28:32, remyoudompheng wrote:
>
>> What is the order of magnitude of the savings (number of objects, size
>>
> in bytes)
>
>> ?
>>
>
> I am sure the savings are small (the number of interface
> implementations).
> But aside from increasing load on GC, they also pin MSpan's in memory.
> I.e. if a MSpan is unlucky to hold 1 such object, the span will never
> reused or returned to OS.
> And on top of that, I think it's just the right way to do it -- allocate
> persistent objects with persistentalloc.
>
>
>
>
https://codereview.appspot.**com/10139043/<https://codereview.appspot.com/101...
>
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[dvyukov, 2013-06-09 17:58:53]

*** Submitted as https://code.google.com/p/go/source/detail?r=8257d3f823ee ***

runtime: use persistentalloc instead of mallocgc for itab
Reduces heap size.

R=golang-dev, remyoudompheng, bradfitz
CC=golang-dev
https://codereview.appspot.com/10139043