• Hiraku Toyooka's avatar
    tracing: Make a snapshot feature available from userspace · debdd57f
    Hiraku Toyooka authored
    Ftrace has a snapshot feature available from kernel space and
    latency tracers (e.g. irqsoff) are using it. This patch enables
    user applictions to take a snapshot via debugfs.
    Add "snapshot" debugfs file in "tracing" directory.
        This is used to take a snapshot and to read the output of the
         # echo 1 > snapshot
        This will allocate the spare buffer for snapshot (if it is
        not allocated), and take a snapshot.
         # cat snapshot
        This will show contents of the snapshot.
         # echo 0 > snapshot
        This will free the snapshot if it is allocated.
        Any other positive values will clear the snapshot contents if
        the snapshot is allocated, or return EINVAL if it is not allocated.
    Link: http://lkml.kernel.org/r/20121226025300.3252.86850.stgit@liselsia
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: David Sharp <dhsharp@google.com>
    Signed-off-by: default avatarHiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
       Fixed irqsoff selftest and also a conflict with a change
       that fixes the update_max_tr.
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
trace.h 26.7 KB