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From "Sander Striker" <stri...@apache.org>
Subject RE: SMS usage patterns, hierarchies
Date Tue, 10 Jul 2001 22:01:50 GMT
> Thanks.  If I'm reading the graphs right, they show
> that destruction of a leaf SMS with siblings is much
> more common than destruction or reset of a non-leaf
> SMS with children.  That seems to reinforce the
> conclusion I drew from gprof data: we could get better
> performance by allocating blocks for a child from
> something that isn't the direct parent (like a per-CPU
> free list, based on Dean's recommendation).

I want to discuss this some more to be honest.  There
are several options we can try and I feel it is best
to examine more than one, even though one looks like
the way to go.  A per-CPU free list will be difficult
to implement for reasons Justin pointed out.
A per thread free list is a lot easier.  Actually, if
we use an sms like "tracking" instead of "trivial" we get
one free list.  If we then use the "threads" sms (which
I should commit (I'll wait until Davids patch is in))
as the parent sms of all the top level smss in each
thread, we get a free list per thread.  But, this
requires tweaking httpd, which right now is not really
an option.
> But stop me if I've misinterpreted the data...

Well, you could read it differently.  Look at images
233 to 259, then look at 260.  Now why are all those
destroyed individually, when one destroy, the one in
260 could take care of them all?

There are some more examples of that in there I believe.
Worth examining?

> --Brian


PS. If anyone is interested I can try and get some more
    information in there, like the number of allocations,
    the number of times it was reset.  With a bit more
    effort the file/lineno of where the call was made.

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