[haiku-appserver] Re: Shared Memory Allocation

  • From: "DarkWyrm" <bpmagic@xxxxxxxxxxxxxxx>
  • To: haiku-appserver@xxxxxxxxxxxxx
  • Date: Sat, 04 Sep 2004 12:29:31 -0400 EDT

> "DarkWyrm" <bpmagic@xxxxxxxxxxxxxxx> wrote:
> > I just changed our pool allocator from a bunch of C code (and ugly 
> > at 
> > that) to a class so we can have multiple pool managers in the same 
> > application without conflicts. We are going the same route as R5 
> > and 
> > setting up a general application area. We will eventually be moving 
> > BBitmap storage to this shared area to prevent a bad app from 
> > overwriting BBitmap data in another app, but one question still 
> > remains: how should we send over a large object? Should we create a 
> > new 
> > area, dump it there, and tell the server to look there, or should 
> > the 
> > client ask the app_server for a memory chunk to write to, write to 
> > it, 
> > and then send the message? I'm kinda concerned about overhead and I 
> > wondered what the rest of you gentlemen thought.
> 
> You can create the area in the client, send its area_id to the 
> server, 
> clone it there, and delete the area in the client, if you don't need 
> to 
> access it anymore from there.
> Does that fit to what you need?
That was already part of the plan. The problem is how to manage 
allocating and deleting memory from this shared space. We already have 
a working pool allocator to handle the actual management, but what 
would be the best route to go to allow both sides to do this. Perhaps I 
can illustrate better with an example. Let's say that we have someone 
who is incredibly stupid or incredibly evil (or both) who wants to 
approximate a particular strange BShape using a BPolygon object and 
does so by storing literally each and every point in the thing and, as 
a result, the thing occupies 2MB of space. Ouch. Then he tries to draw 
it using StrokePolygon. Somehow that data needs to get to the server. 
The only problem is that AFAIK there isn't a way for that much data to 
fit through a port. Ideally, I'd like to have some way to put the whole 
AS_STROKE_POLYGON message into an area, and then tell the server where 
it is. Then, the server only has to look in the area to read the whole 
thing in -- or perhaps make the call directly from the data in the area 
to avoid another copy -- and then delete the whole mess so that the 
memory is freed. How could something like this be coordinated? Is there 
a better way that I haven't yet thought of?

--DW

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