Hello all,
I am doing some more porting and hitting some trouble spots - no real surprise
that they exist. However, I am struck by a strong belief that Dolphin has a
lot of things right, and startup and shutdown is very high on that list.
No offense to Nicolas, who has been quite helpful, let's consider a somewhat
extrmeme example. Suppose a server is using an ORB to do SSL protected
communications with various servers and clients, some Seaside work, and has a
few database connections open. Are we content with having to close and reopen
all of that just to save the image? I submit that this is a flawed design.
Worst case, the vm knows when it loads an image and could tell the image that
it happened. From there, a lot of extra work could be dumped.
Nicolas is quite right that step (2) below must be done carefully, but it has
been handled nicely in Dolphin by registering potential offenders in the
startup triggers and doing the cleanup at that time. External resources are
released on a shutdown trigger, but not image save. This will strike again
with native windows, as the current approach would (stop me if this is a
fallacy) have everything released and reopened on image save, which would be
very inefficient.
I have code that expects a class called SessionManager, and I am seriously
thinking of creating it. It would trigger events for starup and shutdown, help
with logging, etc. Can it be donw without hacking the vm?
Bill
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[Pharo-project] Save and quit vs. Save - a clue to performance???
Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Thu Jul 16 22:48:34 CEST 2009
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Current policy is to cleanup before saving, and reconnect after saving
as if a fresh startup occured
As you seem to suggest, a possible alternative without using fork would be to:
1) distinguish whether this is a newly restarted image (primSnapshot
returning true or false...)
2) perform all the clean-ups at startup if newly restarted image
3) rely on the process exit() to perform required resource clean-up in
case we quit (or let a self aboutToQuit do some)
Step 2) would deserve great care, any unprotected access to an
uninitialized pointer of the old image would crash or trash memory...
Nicolas
2009/7/16 Schwab,Wilhelm K <bschwab at anest.ufl.edu>:
> Nicolas,
>
> One thing I forgot to mention: thread safety??? IIRC, Dolphin triggers
> startup events, and all external resources clear pointers then (though they
> will release on shutdown, not image saving) to force a lazy connection.
>
> I see why, absent help from the vm, the image does not know when it starts
> and stops. What I do not get is why the vm does not tell it. If it did, I
> _think_ we could clean all of this up. Sometimes the truth hurts though, so
> please find any faults in my logic (or lack thereof).
>
> Bill
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