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Date: Tue, 11 Feb 2003 19:05:15 -0600
From: Min Xu <mxu@cae.wisc.edu>
To: dev@httpd.apache.org
Subject: Re: Strange Behavior of Apache 2.0.43 on SPARC MP system
Message-ID: <20030212010513.GA11807@mail.cae.wisc.edu>
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On Tue, Feb 11, 2003 at 03:11:36PM -0800, David Burry wrote:
> Because the client will contend very heavily with the server for many
> system resources.  It's indeterminate which one (client or server)
> requires more resources, which one wins more, and how much more of which
> resources.

Well, I am not defending this server/client-on-one-system is better
or anything. Just want to understand this better. Isn't the clients
block when the servers can not response? From a higher level of point
of view, the system is a closed queuing system. In the steady state
there should be a balance between servers and clients, right?

> Running both on the same machine will certainly stress the
> machine pretty well, but you can't compare any measurement you get with
> what the same machine will perform if Apache doesn't have to contend
> with a client for its resources, it won't be the same result at all.

We have no intention to compare these two at all. Our goal was to
achieve a reasonable workload that runs similarly as the real world
application.

> In
> the real world apache doesn't have a client stealing its system
> resources, therefore an accurate test of how apache would behave in the
> real world can only be done if you set up a test with the same
> situation.  This could be why apache is performing better when you let
> your client sleep a little (then again, it could be something else,
> that's why I say it's "indeterminate" (unknown) how much of the
> resources the client itself is stealing away from the server).  To
> measure the effect of anything, you have to limit the number of
> variables that can influence the result.

I agree. We indeed tried other experiments to test this hypothesis.
We first used separate machines for the clients and this behavior
disappeared. But I think the reason was the network(ethernet) latency
between those server and client machines enssentially served as the
small delay time I have added in the singal machine case. On the other
hand, I have used solaris "psrset" to logically divide the 14p server
into "two" machines, and I bind the server and the client to different
processor sets. And the results shows again the small delay time have
important impact on system throughput.

How strange!

-- 
Rapid keystrokes and painless deletions often leave a writer satisfied with
work that is merely competent.
  -- "Writing Well" Donald Hall and Sven Birkerts