[lkml]   [2003]   [Oct]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [2.6 patch] add a config option for -Os compilation
    Martin J. Bligh wrote:
    > But if someone with a small cache would actually *measure* the damned
    > thing, I'd be more impressed ... I've never seen that, but perhaps
    > I just missed it.
    > Point is the same either way though ... we shouldn't unconditionally
    > optimise for *anyone's* system. If it's faster on all systems that anyone
    > can be bothered to measure, great. If it's faster on some, and slower on
    > others, a config option seems more appropriate, defaulting to the majority
    > of users.

    The thing is, that in fact kernel optimization is not that important.

    The goal of kernel is to provide framework for applications to the
    job well. I wasn't doing any kernels measurements - since kernel docs
    are saying that -O2 is the standard. And it is really hard to measure
    kernel only perfomance. (And it is rather pointless - I'm not going to
    sell linux kernel ;-)))

    But indeed I was testing my application on embedded system with 16K
    L1 cache. Results were pretty predictable: gcc 2.95.3 + -Os was giving
    some (around 2-3%) performance improvements, while 2.95.3 + -O[23] and
    3.2.3 with any optimization were giving aprox. the same times. (App is
    bloated with third-party libraries, C++ and threads. Save God I have
    killed all exceptions - they were really really really slow on target

    But on other side - since embedded systems are not that overclocked
    as high-end toys - cache miss is not that painful. As of docs, NatSemi
    Geode@266MHz cache miss costs exactly 266/66 == 4 cycles.

    Ihar 'Philips' Filipau / with best regards from Saarbruecken.
    "... and for $64000 question, could you get yourself vaguely
    familiar with the notion of on-topic posting?"
    -- Al Viro @ LKML

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 13:58    [W:0.021 / U:106.796 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site