Dieter Maurer wrote:

Jens Vagelpohl wrote at 2006-1-31 15:07 +0000:On 31 Jan 2006, at 15:01, Jake wrote:http://plone.org/documentation/how-to/threads-vs-cache-sizeThat article contains little information to back up the conclusions,and some of it is patently wrong. Another case of hearsay and half-thruths being propagated by well-meaning but uninformed parties.There is a convincing example (I think from Matt Kromer) what happens to "mean response time" when the number of threads is increased from 1 to 2: Assume you have 2 units of work. If you have a single thread, 1 unit is done, then the second. The mean response time is (1 + 2) / 2 = 1.5. Now assume you have two threads (but a single processor). Both threads work (quasi) parallel but have only half of the processor power. Both will take 2 time units to perform their unit of work. The mean response time is (2 + 2) / 2 = 2.

`This is specious reasoning from a statistical point of view. You never`

`have only two requests. To have a proper statistical evaluation, you`

`need a theoretical model of the distribution of requests over time. This`

`can be as simple as "a request every t". Then you have a continuous flow`

`of requests, and the two means become equal.`

`Just try it with 4 units of work and equivalent time distribution as in`

`the original example:`

- Case 1: (1+2+3+4)/4 = 2.5 - Case 2: (2+2+4+4)/4 = 3 If you generalize to n units of work, you'll get (the math is simple): - Case 1: n(n+1)/2n = n/2+0.5 - Case 2: 4((n/2)(n/2+1)/2)/n = n/2+1 Which are equivalent to n/2 when n grows. Florent -- Florent Guillaume, Nuxeo (Paris, France) Director of R&D +33 1 40 33 71 59 http://nuxeo.com [EMAIL PROTECTED] _______________________________________________ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! **

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