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Description of problem:
oprofile can't sample multiple events, due to what seems to be a missing kernel patch (commit 6b77df08a36d989f7dd00ccb6a026a0e96170d16).

opcontrol understand multiple events, but on el5, only one event is actually caught. The problem has been found by others, using oprofile 0.9.3 on a 2.6.18-8.1.15-kernel (http://www.nabble.com/I-can-not-sample-multiple-events-with-0.9.3-on-X86_64!!-td13579481.html).

Although I have not yet explicitly verified the patch in question on the 2.6.18-53.1.6-kernel, to me, it seems plausible that it would fix the problem.  

Version-Release number of selected component (if applicable):
kernel-2.6.18-53.1.6.el5

How reproducible:
Always


Steps to Reproduce:
1.
# opcontrol --no-vmlinux --event FLOPS:10000 --event CPU_CLK_UNHALTED

2.
# opcontrol --status
Daemon not running
Event 0: FLOPS:10000:0:1:1
Event 1: CPU_CLK_UNHALTED:100000:0:1:1
Separate options: library
vmlinux file: none
Image filter: none
Call-graph depth: 0

3.
# opcontrol --start ; sleep 10 ; opcontrol --stop
Using 2.6+ OProfile kernel interface.
Using log file /var/lib/oprofile/oprofiled.log
Daemon started.
Profiler running.
Stopping profiling.

4.
# opreport -t 1


Actual Results:
CPU: Core 2, speed 2333.42 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
CPU_CLK_UNHALT...|
  samples|      %|
------------------
    27064 35.6129 no-vmlinux
    24430 32.1469 umath.so
...

Expected Results:
# opreport -t 1
CPU: Core 2, speed 1000 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
Counted FLOPS events (number of FP computational micro-ops executed) with a unit mask of 0x00 (No unit mask) count 10000
CPU_CLK_UNHALT...|      FLOPS:10000|
  samples|      %|  samples|      %|
------------------------------------
    10292 65.4291       125 46.4684 no-vmlinux
     2432 15.4609        23  8.5502 firefox-bin
...


Additional info:
commit 6b77df08a36d989f7dd00ccb6a026a0e96170d16
Author: Arun Sharma <arun.sharma>
Date:   Fri Sep 29 02:00:01 2006 -0700

    [PATCH] oprofile: ppro: need to enable/disable all the counters
    
    Need to enable/disable all the counters instead of just counter 0.
    
    This affects all cpus with family=6, including i386/core.  Usual symptom:
    only counter 0 provides samples.  Other counters don't produce samples.
    
    Signed-off-by: Arun Sharma <arun.sharma>
    Cc: Philippe Elie <phil.el>
    Cc: John Levon <levon>
    Signed-off-by: Andrew Morton <akpm>
    Signed-off-by: Linus Torvalds <torvalds>

diff --git a/arch/i386/oprofile/op_model_ppro.c b/arch/i386/oprofile/op_model_ppro.c
index f88e05b..ca2447e 100644
--- a/arch/i386/oprofile/op_model_ppro.c
+++ b/arch/i386/oprofile/op_model_ppro.c
@@ -138,11 +138,14 @@ static int ppro_check_ctrs(struct pt_regs * const regs,
 static void ppro_start(struct op_msrs const * const msrs)
 {
  unsigned int low,high;
+ int i;
 
- if (reset_value[0]) {
- CTRL_READ(low, high, msrs, 0);
- CTRL_SET_ACTIVE(low);
- CTRL_WRITE(low, high, msrs, 0);
+ for (i = 0; i < NUM_COUNTERS; ++i) {
+ if (reset_value[i]) {
+ CTRL_READ(low, high, msrs, i);
+ CTRL_SET_ACTIVE(low);
+ CTRL_WRITE(low, high, msrs, i);
+ }
  }
 }
 
@@ -150,11 +153,14 @@ static void ppro_start(struct op_msrs const * const msrs)
 static void ppro_stop(struct op_msrs const * const msrs)
 {
  unsigned int low,high;
+ int i;
 
- if (reset_value[0]) {
- CTRL_READ(low, high, msrs, 0);
+ for (i = 0; i < NUM_COUNTERS; ++i) {
+ if (!reset_value[i])
+ continue;
+ CTRL_READ(low, high, msrs, i);
  CTRL_SET_INACTIVE(low);
- CTRL_WRITE(low, high, msrs, 0);
+ CTRL_WRITE(low, high, msrs, i);
  }
 }