Linux-kernel mailing list archive 1999-41,: Re: More on bigger kdev_t

# Re: More on bigger kdev_t

Jeff Garzik (jgarzik@pobox.com)
Sun, 10 Oct 1999 16:35:37 -0400

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Martin Dalecki wrote:
> I have tryed the direct approach to kdev_t several years ago out.
> The lost in speed caused by introducing the strcut was really noticable
> in the overall device system's performance.
>
> It was about scary several percents. Sorry I'm not quite
> sure if my memmory leaves me, but it was about as much as 3% on a
> 486/66MHz (Yes It was that long ago...)
> And this after only folding the arrays indexed by MINOR(dev) into a
> single
> array of corresponding structs.

Just to be clear, you replaced kdev_t with a struct, or a ptr to a
struct?

And what did you do with the arrays indexed by MINOR(dev)? Andries
pointed out that a linear search for a major/minor could be ugly and
slow, potentially causing the slowdown you mention.

Regards,

Jeff

    --
    Custom driver development	|    Never worry about theory as long
    Open source programming		|    as the machinery does what it's
    				|    supposed to do.  -- R. A. Heinlein

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