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    SubjectRe: [PATCH 00/10][RFC] tracing: Lowering the footprint of TRACE_EVENTs
    Steven Rostedt wrote:
    > This is an RFC patch set that also affects kprobes and perf.
    > At the Linux Collaboration Summit, I talked with Mathieu and others about
    > lowering the footprint of trace events. I spent all of last week
    > trying to get the size as small as I could.
    > Currently, each TRACE_EVENT() macro adds 1 - 5K per tracepoint. I got various
    > results by adding a TRACE_EVENT() with the compiler, depending on
    > config options that did not seem related. The new tracepoint I added
    > would add between 1 and 5K, but I did not investigate enough to
    > see what the true size was.
    > What was consistent, was the DEFINE_EVENT(). Currently, it adds
    > a little over 700 bytes per DEFINE_EVENT().
    > This patch series does not seem to affect TRACE_EVENT() much (had
    > the same various sizes), but consistently brings DEFINE_EVENT()s
    > down from 700 bytes to 250 bytes per DEFINE_EVENT(). Since syscalls
    > use one "class" and are equivalent to DEFINE_EVENT() this can
    > be a significant savings.
    > With events and syscalls (82 events and 616 syscalls), before this
    > patch series, the size of vmlinux was: 16161794, and afterward: 16058182.
    > That is 103,612 bytes in savings! (over 100K)
    > Without tracing syscalls (82 events), it brought the size of vmlinux
    > down from 1591046 to 15999394.
    > 22,071 bytes in savings.
    > This is just an RFC (for now), to get peoples opinions on the changes.
    > It does a bit of rewriting of the CPP macros, just to warning you ;-)

    Hm, at least for kprobe tracer, this change is ok,
    even though it isn't much worth as for tracepoints.
    I think, if we have ftrace_event_ops, it will help reducing
    the size of dynamic events a bit (not so much).

    Thank you,

    Masami Hiramatsu

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