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ring-buffer: User context bit recursion checking

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Using context bit recursion checking, we can help increase the
performance of the ring buffer.

Before this patch:

 # echo function > /debug/tracing/current_tracer
 # for i in `seq 10`; do ./hackbench 50; done
Time: 10.285
Time: 10.407
Time: 10.243
Time: 10.372
Time: 10.380
Time: 10.198
Time: 10.272
Time: 10.354
Time: 10.248
Time: 10.253

(average: 10.3012)

Now we have:

 # echo function > /debug/tracing/current_tracer
 # for i in `seq 10`; do ./hackbench 50; done
Time: 9.712
Time: 9.824
Time: 9.861
Time: 9.827
Time: 9.962
Time: 9.905
Time: 9.886
Time: 10.088
Time: 9.861
Time: 9.834

(average: 9.876)

 a 4% savings!

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt
2012-11-02 18:33:05 -04:00
committed by Steven Rostedt
parent 897f68a48b
commit 567cd4da54
2 changed files with 69 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
kernel/trace/trace.h
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@@ -291,11 +291,6 @@ struct tracer {
/* Only current can touch trace_recursion */
#define trace_recursion_inc() do { (current)->trace_recursion++; } while (0)
#define trace_recursion_dec() do { (current)->trace_recursion--; } while (0)
/* Ring buffer has the 10 LSB bits to count */
#define trace_recursion_buffer() ((current)->trace_recursion & 0x3ff)
/*
* For function tracing recursion:
@@ -323,7 +318,13 @@ struct tracer {
* caller, and we can skip the current check.
*/
enum {
TRACE_FTRACE_BIT = 11,
TRACE_BUFFER_BIT,
TRACE_BUFFER_NMI_BIT,
TRACE_BUFFER_IRQ_BIT,
TRACE_BUFFER_SIRQ_BIT,
/* Start of function recursion bits */
TRACE_FTRACE_BIT,
TRACE_FTRACE_NMI_BIT,
TRACE_FTRACE_IRQ_BIT,
TRACE_FTRACE_SIRQ_BIT,