[lkml]   [2009]   [Apr]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH 2/8] tracing: create automated trace defines
    * Jeremy Fitzhardinge ( wrote:
    > Mathieu Desnoyers wrote:
    >> The other point I dislike about the out-of-line approach is that the
    >> tracer will suffer from a pointless supplementary function call at each
    >> event. Given how slow function calls are, at least on x86, I'd prefer
    >> leaving the handler call chain inline, unless there is a very strong
    >> reason not to do so.
    > Are they? They're generally considered to be "free", because the call
    > and return are predicted 100% accurately.

    Adding a simple function call within the tracer fast path, in LTTng, has
    a very measurable performance impact on the tbench workload. This is why
    I don't use any function call-based trace clocks in LTTng, but rather my
    own inline trace clock.


    >> I'll come up with a patch that leaves the tracepoint inline, but fixes
    >> the header dependency.
    > OK.
    > J

    Mathieu Desnoyers
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68

     \ /
      Last update: 2009-04-17 02:15    [W:0.026 / U:21.976 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site