Thanks Adrian and Mariano for this interesting discussion.
Alexandre
On 29 Mar 2010, at 16:23, Mariano Martinez Peck wrote:
On Mon, Mar 29, 2010 at 5:12 PM, Adrian Lienhard <[email protected]>
wrote:
On Mar 29, 2010, at 21:52 , Mariano Martinez Peck wrote:
> 2010/3/29 John M McIntosh <[email protected]>
>
>> Also this week I will ship a 4.2.4b1 VM which is the result of
some Squeak
>> 4.0 base VM merge processing and contains the fix to enable the
loading of
>> old image segments used I guess by squeakmap?
>>
>>
>
> I am not sure. ImageSegment is a full of c...and maybe it will be
even
> removed. It was not working since a lot of time and nobody says
anything.
Mariano, I know you know image segments, but I think this is may be
confusing for others. So I like to say something ;)
Image segments work very well; both from a reliability and
performance point of view. We are using them for hundreds of
customers. DabbleDB uses images segments as well AFAIK.
There are two parts, the primitives implemented by the VM in C and
the image-side code. The code in the image consists of support code
to load and store a segment and on top of this there is code for
swapping in/out classes, projects etc. Especially the latter is a
mess and we already started cleaning it. As images segments are not
used by core code we also consider moving it into a separate,
external package (of course, the primitives should stay in the VM).
Thanks for the remark Adrian :) I know you know more for
ImageSegments than all of us.
As you said, it works pretty well for a piece of the domain. For
example, in your case, you just export the segment, but did you try
to swap them out (but letting the segment inside) and load it
again ? it was broken. Exporting a segment, and bring them back
again but where classes were modified or removed in the image, was
broken also. If you load segments from older versions, it was broken
too (this was what they fixed now). The symbols, you explained me
that problem. In your case it works perfect because, as you say,
almost only use the primitives, no more. But that's a very limited
piece of ImageSegment. That piece, in that way, it works.
For big segments, I am not sure if it works well neither. The
segment allocates more than 2 times what needed. In DabbleDB I read
they had that problem. The segments were too big, that having to
allocate 2 or 3 times, crash everything.
Cheers
Mariano
> We
> even started to remove part of it in Pharo. And SqueakMap was
completely
> removed.
Yes, SqueakMap is not relevant anymore for Pharo. Hence, this VM fix
is not critical for us.
Cheers,
Adrian
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