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From "Paul J. Reder" <rede...@raleigh.ibm.com>
Subject Re: Scoreboard redesign
Date Thu, 17 May 2001 15:42:58 GMT
rbb@covalent.net wrote:
> > hmmm...more thought, code reading, and whiteboard doodling is called
> > for.  Off the top of my head, I would think one of the config hooks in
> > mod_status could allocate a big chuck of shmem for its use on every
> > restart.  Then the new worker processes would see the Right Stuff as far
> 
> You can't allocate on every restart, because if you do, the information
> won't survive a restart.  Imagine the pathological case, where a single
> request is very long-lived, and it happens to survive multiple restarts.
> If we reallocate during each restart, we will lose the status of that
> request.
> 
> > as pointers.  The core should also allocate a new chunk of shmem to
> > represent the processes at restart time, so we can get rid of the
> > HARD_SERVER_LIMIT stuff (it's a PITA...think of admins in big shops who
> 
> Again, you can't do that, for the same reason as the one listed above.
> 
> > want to use binaries).  Getting rid of the shmem for the previous
> > generation might be the most challenging problem.

If your concern is one of losing track of scoreboard entries for long
lived requests this is handled by having the process_score structures
linked together. New ones are added to the head of the list, old ones
are left at the tail. A long lived request would be represented by its
process_score and corresponding worker_score elements linked at the end
of the list until the request is finished. This, of course, assumes that
elements from one shared allocation can point to elements from another.

If your concern is one of lost information after the request finishes and
is finally cleaned up, then perhaps we need to think about combining the 
totals up to a higher level before the element is cleaned up.

Getting rid of the HARD_SERVER_LIMIT is *not* one of my main goals here.
If the design allows its removal then I consider it a benefit. If it
cannot be removed then I don't care. Worrying about trying to make that
happen, especially if it makes the design unreasonable, is a red herring.

-- 
Paul J. Reder
-----------------------------------------------------------
"The strength of the Constitution lies entirely in the determination of each
citizen to defend it.  Only if every single citizen feels duty bound to do
his share in this defense are the constitutional rights secure."
-- Albert Einstein

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