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tracing: Reduce latency and remove percpu trace_seq

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__print_flags() and __print_symbolic() use percpu trace_seq:

1) Its memory is allocated at compile time, it wastes memory if we don't use tracing.
2) It is percpu data and it wastes more memory for multi-cpus system.
3) It disables preemption when it executes its core routine
   "trace_seq_printf(s, "%s: ", #call);" and introduces latency.

So we move this trace_seq to struct trace_iterator.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4C078350.7090106@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Lai Jiangshan
2010-06-03 18:26:24 +08:00
committed by Steven Rostedt
parent 985023dee6
commit bc289ae98b
3 changed files with 6 additions and 14 deletions
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5
include/linux/ftrace_event.h
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@@ -11,8 +11,6 @@ struct trace_array;
struct tracer;
struct dentry;
DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);
struct trace_print_flags {
unsigned long mask;
const char *name;
@@ -58,6 +56,9 @@ struct trace_iterator {
struct ring_buffer_iter *buffer_iter[NR_CPUS];
unsigned long iter_flags;
/* trace_seq for __print_flags() and __print_symbolic() etc. */
struct trace_seq tmp_seq;
/* The below is zeroed out in pipe_read */
struct trace_seq seq;
struct trace_entry *ent;