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Subject[PATCH 00/10 final] tracing: Lowering the footprint of TRACE_EVENTs

[ Final final version! ]


This 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 two weeks
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 618 syscalls), before this
patch series, the size of vmlinux was: 6863829, and afterward: 6768675.

That is 95,154 bytes in savings! (over 92K)

Note: I did this series with disabling KERNEL_DEBUG and that made
the effect of savings smaller. The original numbers with KERNEL_DEBUG
options enabled was: orinal-16161794, new-16058182, savings-103612
which was over 100K) This may still be true with KERNEL_DEBUG enabled
but I only tried it this time with it disabled.

But if I go by percentage, this series saves 1.38% where the
KERNEL_DEBUG series only saved 0.64% of the total vmlinux image.

Config for this run can be found here:

Without tracing syscalls (82 events), it brought the size of vmlinux
down from 6617121 to 659870.

18,421 bytes in savings.

Note: Original numbers with KERNEL_DEBUG options enabled:
original-1591046, new-15888394, savings-22071

Final final changes:

o Fixed trace_event.c self tests to use the probe field in the
structure to determine if the event should be tested.
(old regfunc no longer exists)

o Fixed missing ';' in static struct in macro.

o Fixed the trace register functions in net drop monitor to conform
with the new API.

Final changes:

o Updated the change logs to reflect the sizes with KERNEL_DEBUG

o Added Mathieu Desnoyers's Acked-by to the change logs.

Changes in v3:

o Ported to latest tip/tracing/core

o Fixed typo in change log that a comment in LWN noticed:
Wrote: 15999394 when it should have been 15888394.
(Note: these numbers are from the original posting. I need to
redo them again before posting officially).

o Added Mathieu Desnoyers's check_trace patch that will check
the callback to make sure it matches what DECLARE_TRACE() expects

o Added the check_trace to the ftrace and perf callback probes.
Note, kprobes and syscalls do not use the register tracepoint
so they are not affected.

o Moved the define of DECLARE_TRACE() and DECLARE_TRACE_NOARGS()
out of the #ifdef CONFIG_TRACEPOINTS, since they were the same
whether or not CONFIG_TRACEPOINTS was enabled. The internal
__DECLARE_TRACE() changed.

Changes in v2:

o Ported to latest tip/tracing/core

o Removed DECLARE_TRACE_DATA() and made DECLARE_TRACE() have
the ability to pass a data parameter. This makes DECLARE_TRACE()
not work with no args. A new DECLARE_TRACE_NOARGS() has been created
that also allows data to be passed, but does is for tracepoint(void).

o Made the callbacks be "proto, void *data" and typecast the data
within the function.

Please pull the latest tip/tracing/core tree, which can be found at:


Mathieu Desnoyers (1):
tracepoints: Add check trace callback type

Steven Rostedt (9):
tracing: Create class struct for events
tracing: Let tracepoints have data passed to tracepoint callbacks
tracing: Remove per event trace registering
tracing: Move fields from event to class structure
tracing: Move raw_init from events to class
tracing: Allow events to share their print functions
tracing: Move print functions into event class
tracing: Remove duplicate id information in event structure
tracing: Combine event filter_active and enable into single flags field

include/linux/ftrace_event.h | 73 ++++++--
include/linux/syscalls.h | 57 ++----
include/linux/tracepoint.h | 98 ++++++++---
include/trace/ftrace.h | 237 +++++++++---------------
include/trace/syscall.h | 10 +-
kernel/trace/blktrace.c | 138 ++++++++------
kernel/trace/ftrace.c | 7 +-
kernel/trace/kmemtrace.c | 70 +++++---
kernel/trace/trace.c | 9 +-
kernel/trace/trace.h | 5 +-
kernel/trace/trace_event_perf.c | 17 ++-
kernel/trace/trace_events.c | 137 +++++++++-----
kernel/trace/trace_events_filter.c | 28 ++--
kernel/trace/trace_export.c | 16 +-
kernel/trace/trace_functions_graph.c | 13 +-
kernel/trace/trace_kprobe.c | 104 +++++++----
kernel/trace/trace_output.c | 137 +++++++++-----
kernel/trace/trace_output.h | 2 +-
kernel/trace/trace_sched_switch.c | 23 ++-
kernel/trace/trace_sched_wakeup.c | 27 ++--
kernel/trace/trace_syscalls.c | 137 ++++++++++++---
kernel/trace/trace_workqueue.c | 26 ++-
kernel/tracepoint.c | 91 +++++----
net/core/drop_monitor.c | 12 +-
samples/tracepoints/tp-samples-trace.h | 4 +-
samples/tracepoints/tracepoint-probe-sample.c | 13 +-
samples/tracepoints/tracepoint-probe-sample2.c | 7 +-
27 files changed, 890 insertions(+), 608 deletions(-)

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