A question about #become: (was: Re: [squeak-dev] [ANN] Squeak 5)

Eliot Miranda eliot.miranda at gmail.com
Wed Aug 12 18:20:04 UTC 2015

On Wed, Aug 12, 2015 at 11:09 AM, Levente Uzonyi <leves at elte.hu> wrote:

> I wonder if you're creating two forwarders in case of #become:, with
> objects of different size, or just one forwarder for the larger object
> while copying the smaller object over the larger one (when possible).

Right now it's the simplest thing that could possibly work.  I think this
is a great idea though.  It would potentially eliminate the post-become
stack scan if all objects can be becomed either by exchanging contents or
(in one-way) shortening.  Alas I don't have time for this right now.  Any
volunteers interested?

> On Tue, 11 Aug 2015, Eliot Miranda wrote:
> Hi All,
>>     who will update http://squeak.org/downloads/ to include the 5.0
>> release?
>> a) I suggest that the 5.0 all-in-one have a line in the left-hand table
>> that includes the 4.6 release and that it precede the 4.6 release in the
>> list.
>> b) the Trunk link points to TrunkImage.zip which contains a non-Spur
>> image.
>> c) Spur VMs need to be linked to by an added line in the Virtual Machines
>> list.
>> d) Spur imagers need to be included in the Image and Changes list under
>> Custom Installation
>> e) The SqueakV50.sources file also needs to be included in the Current
>> Sources list.
>> f) we could start a History list for the 5.0 line
>> So there are a few things to fix before 5.0 is freely downloadable.
>> On Tue, Aug 11, 2015 at 8:23 PM, Chris Muller <ma.chris.m at gmail.com>
>> wrote:
>>       In the 17 months since Squeak 4.5 was released, a huge development
>>       effort took place to create the next generation virtual-machine for
>>       the Squeak / Pharo / Newspeak family of programming systems.  Squeak
>>       is the modern incarnation of the Smalltalk-80 programming
>> environment
>>       originally developed at the Xerox PARC.
>>       "Squeak 5" introduces this new VM and associated new memory model,
>>       collectively referred to as "Spur".  Presented [1] by Eliot Miranda
>>       and Clément Béra at the 2015 International Symposium on Memory
>>       Management, this new VM affords Squeak applications a significant
>>       boost in performance and memory management.  Among other
>>       optimizations, the #become operation no longer requires a memory
>> scan.
>>       Object pinning and ephemerons are also now supported.  The release
>>       notes [2] provide more details.
>>       The new memory model requires a new image file format.  Although
>> this
>>       new format results in about a 15% increased memory requirement for
>> the
>>       same number of 4.x objects, a new segmented heap allows memory to be
>>       given back to the OS when its no longer needed, a great benefit for
>>       application servers.
>>       As forward compatibility is as important to the Squeak community as
>>       backward compatibility, Squeak 5 is delivers an image with identical
>>       content as the recent 4.6 release.  Although this new Squeak 5 VM
>>       cannot open images saved under the prior 4.x Cog format, objects and
>>       code can be easily exported from the 4.x image and then imported
>> into
>>       Squeak 5.  Applications whose code runs strictly above the Smalltalk
>>       meta layer will prove remarkably compatible with the new format,
>> most
>>       applications will require no changes whatsotever.
>>       Squeak 5 is the result of monumental effort by a tiny group of very
>>       talented people, but its also just the beginning of yet a new
>> effort;
>>       Spur is just a stepping stone to a more ambitious goals planned over
>>       the next five years.
>>       [1] -- A Partial Read Barrier for Efficient Support of Live
>>       Object-oriented Programming
>> http://conf.researchr.org/event/ismm-2015/ismm-2015-papers-a-partial-read-barrier-for-efficient-support-of-live-object-oriented-programming
>>       [2] -- Squeak 5 Release Notes
>>       http://wiki.squeak.org/squeak/6207
>> --
>> _,,,^..^,,,_
>> best, Eliot

best, Eliot
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