[lkml]   [2010]   [Apr]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
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

 \ /
  Last update: 2010-04-28 16:51    [W:0.140 / U:2.152 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site