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From Harrie Hazewinkel <har...@covalent.net>
Subject Re: Scoreboard redesign
Date Fri, 18 May 2001 21:49:57 GMT
Hi all,

While checking out alpha 18. I start believing we have a problem 
in the scoreboard. I hope I am wrong, but maybe someone can 
explain it.

"Paul J. Reder" wrote:
> 
> 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.

I have conecerns that this list will grow and grow and grow and finally
will run out of the scoreboard. Even if you limit the number that
can be added the linked list does add nothing but overhead.
The scoreboard will use a memory foot print for something that can
be done with indices on an array. However, I have a bigger problem
with the portion below.

> 
> 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.

This is my real concern. After rereading this thread I did not
discover a solution here. You mention the solution already and this
is required to provide a real status of the web-server.
Since the parent can control the elements in the linked list I
beleive that the parent should indeed grab a the summary at an
higher level. If this is not done, the server will never provide a
real status.

Due to the changes in the linked list I believe that the usefullness
of  access_count and bytes_served in the worker_score is zero.
Where in the old design only a quick scan over the array would
have been enough, you now  have to walk thru a linked list.
And the linked list was introduced to avoid that for instance
mod_status had to run all the array elements in the scoreboard.

To me this is resulting in zero advantage.
Do I miss something here??

At least it looks to me that in the alpha 18 the overall
statistics will get lost after some time.



Harrie
-- 
address: Covalent Technologies, 645 Howard St, San Francisco, CA - 94105
phone: +1-415-536-5221                               fax:+1-415-536-5210
personal website: http://www.lisanza.net/

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