lkml.org 
[lkml]   [2022]   [Nov]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH v2 3/4] perf build: Use libtraceevent from the system
    On Wed, Nov 30, 2022 at 11:05 AM Namhyung Kim <namhyung@kernel.org> wrote:
    >
    > On Tue, Nov 29, 2022 at 10:30 PM Ian Rogers <irogers@google.com> wrote:
    > >
    > > Remove the LIBTRACEEVENT_DYNAMIC and LIBTRACEFS_DYNAMIC. If
    > > libtraceevent isn't installed or NO_LIBTRACEEVENT=1 is passed to the
    > > build, don't compile in libtraceevent and libtracefs support. This
    > > also disables CONFIG_TRACE that controls "perf
    > > trace". CONFIG_TRACEEVENT is used to control enablement in
    > > Build/Makefiles, HAVE_LIBTRACEEVENT is used in C code. Without
    > > HAVE_LIBTRACEEVENT tracepoints are disabled and as such the commands
    > > kmem, kwork, lock, sched and timechart are removed. The majority of
    > > commands continue to work including "perf test".
    >
    > Maybe we can have a different approach. I guess the trace data
    > access is isolated then we can make dummy interfaces when there's
    > no libtraceevent. This way we don't need to touch every command
    > and let it fail when it's asked.

    Sounds like a worthwhile refactor that can land on top of this change.

    > The motivation is that we should be able to run the sub-commands
    > as much as possible. In fact, we could run 'record' part only on the
    > target machine and pass the data to the host for analysis with a
    > full-fledged perf. Also some commands like 'perf lock contention'
    > can run with or without libtraceevent (using BPF only).

    The issue here is that perf lock contention will use evsel__new_tp and
    internally that uses libtraceevent. As such it is removed without
    HAVE_LIBTRACEEVENT. Without the evsel there's not much perf lock
    contention can do, so rather than litter the code with
    HAVE_LIBTRACEEVENT and for it to be broken, I made the choice just to
    remove it from the no libtraceevent build for now.

    I think it is worth pursuing these patches in the shape they are in so
    that we can land the removal of tools/lib/traceevent and ensure the
    migration away from an out-of-date version of that library.

    Thanks,
    Ian

    > Thanks,
    > Namhyung

    \
     
     \ /
      Last update: 2022-11-30 21:18    [W:6.128 / U:1.024 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site