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    SubjectRe: [patch 10/10] Scheduler profiling - Use immediate values
    On Sat, Jul 07, 2007 at 07:20:12PM +0200, Willy Tarreau wrote:
    > On Sat, Jul 07, 2007 at 07:01:57PM +0200, Adrian Bunk wrote:
    > > On Sat, Jul 07, 2007 at 11:45:20AM -0400, Frank Ch. Eigler wrote:
    >...
    > > You always have to decide between some debug code and some small bit of
    > > performance. There's a reason why options to disable things like BUG()
    > > or printk() are in the kernel config menus hidden behind CONFIG_EMBEDDED
    > > although they obviously have some performance impact.
    >
    > It is not for the CPU performance they can be disabled, but for the code
    > size which is a real problem on embedded system. While you often have
    > mem/cpu_mhz ratios around 1GB/1GHz on servers and desktops, you more often
    > have ratios like 16MB/500MHz which is 1:32 of the former. That's why you
    > optimize for size at the expense of speed on such systems.

    The latter is not true for my two examples.

    CONFIG_PRINTK=n, CONFIG_BUG=n will obviously make the kernel both
    smaller and faster. [1]

    > Regards,
    > Willy

    cu
    Adrian

    [1] faster due to less code to execute and positive cache effects due to
    the smaller code [2]
    [2] whether the "faster" is big enough that it is in any way measurable
    is a different question

    --

    "Is there not promise of rain?" Ling Tan asked suddenly out
    of the darkness. There had been need of rain for many days.
    "Only a promise," Lao Er said.
    Pearl S. Buck - Dragon Seed

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