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    SubjectRe: Performance analysis of Linux Kernel Markers 0.20 for 2.6.17
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    On Sat, 2006-09-30 at 23:42 -0400, Mathieu Desnoyers wrote:
    > * Nicholas Miell (nmiell@comcast.net) wrote:
    > >
    > > Has anyone done any performance measurements with the "regular function
    > > call replaced by a NOP" type of marker?
    > >
    >
    > Here it is (on the same setup as the other tests : Pentium 4, 3 GHz) :
    >
    > * Execute an empty loop
    >
    > - Without marker
    > NR_LOOPS : 10000000
    > time delta (cycles): 15026497
    > cycles per loop : 1.50
    >
    > - With 5 NOPs
    > NR_LOOPS : 100000
    > time delta (cycles): 300157
    > cycles per loop : 3.00
    > added cycles per loop for nops : 3.00-1.50 = 1.50
    >
    >
    > * Execute a loop of memcpy 4096 bytes
    >
    > - Without marker
    > NR_LOOPS : 10000
    > time delta (cycles): 12981555
    > cycles per loop : 1298.16
    >
    > - With 5 NOPs
    > NR_LOOPS : 10000
    > time delta (cycles): 12983925
    > cycles per loop : 1298.39
    > added cycles per loop for nops : 0.23
    >
    >
    > If we compare this approach to the jump-over-call markers (in cycles per loop) :
    >
    > NOPs Jump over call generic Jump over call optimized
    > empty loop 1.50 1.17 2.50
    > memcpy 0.23 2.12 0.07
    >
    >
    >
    > Mathieu

    What about with two NOPs (".byte 0x66, 0x66, 0x90, 0x66, 0x90" - this
    should work with everything) or one (".byte 0x0f, 0x1f, 0x44, 0x00,
    0x00" - AFAIK, this should work with P6 or newer).

    (Sorry, I should have mentioned this the first time.)

    --
    Nicholas Miell <nmiell@comcast.net>

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