[lkml]   [2008]   [Nov]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH 0/4] trace: profiling branches
    On Fri, 2008-11-21 at 02:12 -0500, Steven Rostedt wrote:
    > Ingo,
    > The following patches clean up the unlikely/likely tracer. Namely
    > it consolidates it into a single file called "profile_annotated_branch".
    > It also adds a new profiler. A true branch profiler that profiles all
    > if() statements where the conditional is not a constant. It puts
    > a bit of overhead on the system, but the results seem pretty interesting.
    > The results are placed in "profile_branch".

    I looked at the full version of this, and it looks really slow.. As I
    recall the biggest problem with the -mm version was it's cacheline
    bouncing (pointed out by Ingo), and yours doesn't _seem_ to fix that. In
    fact your version looks a lot worse..

    So really between the two if we want mainline likely profiling the -mm
    version is a better choice.. The reason that version never went into
    mainline is cause neither me or Andrew felt strongly that this was
    useful in more than just -mm ..

    If you look at the output from the profiling long enough it becomes
    clear that it's frequently misleading .. In the short term a certain
    branch might be likely, and in the long term it isn't.. So you can't
    really blindly start converting the annotation..

    I should also mention that I didn't write the -mm version alone, it was
    an effort between three people me, Andrew, and Hua Zhong (CC added)..


     \ /
      Last update: 2008-11-30 12:09    [W:0.019 / U:73.836 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site