The patch titled
Subject: tracing: move trace_handle_return() out of line
has been added to the -mm tree. Its filename is
tracing-move-trace_handle_return-out-of-line.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/tracing-move-trace_handle_return-out-of-line.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/tracing-move-trace_handle_return-out-of-line.patch
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------------------------------------------------------
From: Steven Rostedt <rostedt@xxxxxxxxxxx>
Subject: tracing: move trace_handle_return() out of line
Currently trace_handle_return() looks like this:
static inline enum print_line_t trace_handle_return(struct trace_seq *s)
{
return trace_seq_has_overflowed(s) ?
TRACE_TYPE_PARTIAL_LINE : TRACE_TYPE_HANDLED;
}
Where trace_seq_overflowed(s) is:
static inline bool trace_seq_has_overflowed(struct trace_seq *s)
{
return s->full || seq_buf_has_overflowed(&s->seq);
}
And seq_buf_has_overflowed(&s->seq) is:
static inline bool
seq_buf_has_overflowed(struct seq_buf *s)
{
return s->len > s->size;
}
Making trace_handle_return() into:
return (s->full || (s->seq->len > s->seq->size)) ?
TRACE_TYPE_PARTIAL_LINE :
TRACE_TYPE_HANDLED;
One would think this is not an issue to keep as an inline. But because
this is used in the TRACE_EVENT() macro, it is extended for every
tracepoint in the system. Taking a look at a single tracepoint
x86_irq_vector (was the first one I randomly chosen). As
trace_handle_return is used in the TRACE_EVENT() macro of
trace_raw_output_##call() we disassemble trace_raw_output_x86_irq_vector
and do a diff. I removed identical lines that were different just due to
different addresses.
The original has 22 bytes of text more than the out of line version. As
this is for every TRACE_EVENT() defined in the system, this can become
quite large.
text data bss dec hex filename
8690305 5450490 1298432 15439227 eb957b vmlinux-orig
8681725 5450490 1298432 15430647 eb73f7 vmlinux-handle
This change has a total of 8580 bytes in savings.
$ objdump -dr /tmp/vmlinux-orig | grep '^[0-9a-f]* <trace_raw_output' | wc -l
324
That's 324 tracepoints. But this does not include modules (which contain
many more tracepoints). For an allyesconfig build:
$ objdump -dr vmlinux-allyes-orig | grep '^[0-9a-f]* <trace_raw_output' | wc -l
1401
That's 1401 tracepoints giving us:
text data bss dec hex filename
137827709 140221067 53264384 331313160 13bf7008 vmlinux-allyes-handle
137920629 140221067 53264384 331406080 13c0db00 vmlinux-allyes-orig
92920 bytes in savings!!!
Link: http://lkml.kernel.org/r/20170315021431.13107-2-andi@xxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20170316113459.2366588b@xxxxxxxxxxxxxxxxxx
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Reported-by: Andi Kleen <andi@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/trace_events.h | 11 +----------
kernel/trace/trace.c | 12 ++++++++++++
2 files changed, 13 insertions(+), 10 deletions(-)
diff -puN include/linux/trace_events.h~tracing-move-trace_handle_return-out-of-line include/linux/trace_events.h
--- a/include/linux/trace_events.h~tracing-move-trace_handle_return-out-of-line
+++ a/include/linux/trace_events.h
@@ -138,16 +138,7 @@ enum print_line_t {
TRACE_TYPE_NO_CONSUME = 3 /* Handled but ask to not consume */
};
-/*
- * Several functions return TRACE_TYPE_PARTIAL_LINE if the trace_seq
- * overflowed, and TRACE_TYPE_HANDLED otherwise. This helper function
- * simplifies those functions and keeps them in sync.
- */
-static inline enum print_line_t trace_handle_return(struct trace_seq *s)
-{
- return trace_seq_has_overflowed(s) ?
- TRACE_TYPE_PARTIAL_LINE : TRACE_TYPE_HANDLED;
-}
+enum print_line_t trace_handle_return(struct trace_seq *s);
void tracing_generic_entry_update(struct trace_entry *entry,
unsigned long flags,
diff -puN kernel/trace/trace.c~tracing-move-trace_handle_return-out-of-line kernel/trace/trace.c
--- a/kernel/trace/trace.c~tracing-move-trace_handle_return-out-of-line
+++ a/kernel/trace/trace.c
@@ -1927,6 +1927,18 @@ void tracing_record_cmdline(struct task_
__this_cpu_write(trace_cmdline_save, false);
}
+/*
+ * Several functions return TRACE_TYPE_PARTIAL_LINE if the trace_seq
+ * overflowed, and TRACE_TYPE_HANDLED otherwise. This helper function
+ * simplifies those functions and keeps them in sync.
+ */
+enum print_line_t trace_handle_return(struct trace_seq *s)
+{
+ return trace_seq_has_overflowed(s) ?
+ TRACE_TYPE_PARTIAL_LINE : TRACE_TYPE_HANDLED;
+}
+EXPORT_SYMBOL_GPL(trace_handle_return);
+
void
tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
int pc)
_
Patches currently in -mm which might be from rostedt@xxxxxxxxxxx are
tracing-move-trace_handle_return-out-of-line.patch
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