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    SubjectRe: [ANNOUNCE] ktimers subsystem
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    On Sat, 2005-09-24 at 15:56 +0200, Thomas Gleixner wrote:
    > On Sat, 2005-09-24 at 12:35 +0200, Roman Zippel wrote:
    > > Hi,
    > >
    > > On Sat, 24 Sep 2005, Ingo Molnar wrote:
    > >
    > > > > Anyway, the biggest cost is the conversion from/to the 64bit ns value
    > > > > [...]
    > > >
    > > > Where do you get that notion from? Have you personally measured the
    > > > performance and code size impact of it? If yes, would you mind to share
    > > > the resulting data with us?
    > > >
    > > > Our data is that the use of 64-bit nsec_t significantly reduces the size
    > > > of a representative piece of code (object size in bytes):
    > > >
    > > > AMD64 I386 ARM PPC32 M68K
    > > > nsec_t_ops 226 284 252 428 206
    > > > timespec_ops 412 324 448 640 342
    > > >
    > > > i.e. a ~40% size reduction when going to nsec_t on m68k, in that
    > > > particular function. Even larger, ~45% code size reduction on a true
    > > > 64-bit platform.
    > >
    > > Without any source these numbers are not verifiable. You don't even
    > > mention here what that "representative piece of code" is...

    These numbers are misleading .. Doing a total code comparison shows that
    a 2.6.14-rc2+ktimers kernel is slightly bigger than a vanilla 2.6.14-rc2
    kernel (gcc 4.0, defconfig) .. So your argument that "small is faster"
    must mean ktimers is slower, or at least not faster ..

    Making a speed argument based on code size doesn't make much sense to
    me, if it's actually faster then show that it's faster.

    Daniel


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