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Re: [CPROG] En ordentlig timing



On Sat, 3 Nov 2001, Peter Aagaard Kristensen wrote:

>  >En løkke omkring en sammenligning med gettimeofday() (som er både
>  >hurtig og med høj præcision) er umiddelbart mit bedste bud, men stadig
>  >ikke til de tidsintervaller, du snakkede om. Du kan også se på
>  >select()/pselect(), som måske er lidt mere portable.
> Hvis gettimeofday() er nogenlunde præcis så kan den godt bruges
> til at time busywait med.

Nej, nu må det snart holde op. Der bliver snakket om at time perioder på
100ns. gettimeofday er et kernekald. At kalde kernen har formentlig et
overhead i mikrosekund området, altså en faktor 10 værre, minimum.

> 
>  >Men jeg havde forstået, at den aktuelle relevans var forsvundet?
> Hvis IO-Howto'en holder så ja. Men jeg kan ikke finde anden
> dokumentation på at der er 1ms forsinkelse på skrivning til
> IO porte.

Kan du ikke give en reference til der hvor du har læst det?

Mads

-- 
Mads Bondo Dydensborg.                               sslug@sslug
Sure, some companies might run successful businesses by making Linux easier
to use and offering technical support for the systems, but no business model
based on service and support is ever going to approach the incredible level
of profitability of a Microsoft-style 'pay us for breathing' business
                               - Pat Dorsey, Morningstar



 
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