• Steven Rostedt's avatar
    tracing: Move fields from event to class structure · 2e33af02
    Steven Rostedt authored
    Move the defined fields from the event to the class structure.
    Since the fields of the event are defined by the class they belong
    to, it makes sense to have the class hold the information instead
    of the individual events. The events of the same class would just
    hold duplicate information.
    After this change the size of the kernel dropped another 3K:
       text	   data	    bss	    dec	    hex	filename
    4913961	1088356	 861512	6863829	 68bbd5	vmlinux.orig
    4900252	1057412	 861512	6819176	 680d68	vmlinux.regs
    4900375	1053380	 861512	6815267	 67fe23	vmlinux.fields
    Although the text increased, this was mainly due to the C files
    having to adapt to the change. This is a constant increase, where
    new tracepoints will not increase the Text. But the big drop is
    in the data size (as well as needed allocations to hold the fields).
    This will give even more savings as more tracepoints are created.
    Note, if just TRACE_EVENT()s are used and not DECLARE_EVENT_CLASS()
    with several DEFINE_EVENT()s, then the savings will be lost. But
    we are pushing developers to consolidate events with DEFINE_EVENT()
    so this should not be an issue.
    The kprobes define a unique class to every new event, but are dynamic
    so it should not be a issue.
    The syscalls however have a single class but the fields for the individual
    events are different. The syscalls use a metadata to define the
    fields. I moved the fields list from the event to the metadata and
    added a "get_fields()" function to the class. This function is used
    to find the fields. For normal events and kprobes, get_fields() just
    returns a pointer to the fields list_head in the class. For syscall
    events, it returns the fields list_head in the metadata for the event.
    v2:  Fixed the syscall fields. The syscall metadata needs a list
         of fields for both enter and exit.
    Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Acked-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Acked-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
    Cc: Tom Zanussi <tzanussi@gmail.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
ftrace.h 20.8 KB