perf sched timehist: Add pre-migration wait time option

pre-migration wait time is the time that a task unnecessarily spends
on the runqueue of a CPU but doesn't get switched-in there. In terms
of tracepoints, it is the time between sched:sched_wakeup and
sched:sched_migrate_task.

Let's say a task woke up on CPU2, then it got migrated to CPU4 and
then it's switched-in to CPU4. So, here pre-migration wait time is
time that it was waiting on runqueue of CPU2 after it is woken up.

The general pattern for pre-migration to occur is:
sched:sched_wakeup
sched:sched_migrate_task
sched:sched_switch

The sched:sched_waking event is used to capture the wakeup time,
as it aligns with the existing code and only introduces a negligible
time difference.

pre-migrations are generally not useful and it increases migrations.
This metric would be helpful in testing patches mainly related to wakeup
and load-balancer code paths as better wakeup logic would choose an
optimal CPU where task would be switched-in and thereby reducing pre-
migrations.

The sample output(s) when -P or --pre-migrations is used:
=================
           time    cpu  task name                       wait time  sch delay   run time  pre-mig time
                        [tid/pid]                          (msec)     (msec)     (msec)     (msec)
--------------- ------  ------------------------------  ---------  ---------  ---------  ---------
   38456.720806 [0001]  schbench[28634/28574]               4.917      4.768      1.004      0.000
   38456.720810 [0001]  rcu_preempt[18]                     3.919      0.003      0.004      0.000
   38456.721800 [0006]  schbench[28779/28574]              23.465     23.465      1.999      0.000
   38456.722800 [0002]  schbench[28773/28574]              60.371     60.237      3.955     60.197
   38456.722806 [0001]  schbench[28634/28574]               0.004      0.004      1.996      0.000
   38456.722811 [0001]  rcu_preempt[18]                     1.996      0.005      0.005      0.000
   38456.723800 [0000]  schbench[28833/28574]               4.000      4.000      3.999      0.000
   38456.723800 [0004]  schbench[28762/28574]              42.951     42.839      3.999     39.867
   38456.723802 [0007]  schbench[28812/28574]              43.947     43.817      3.999     40.866
   38456.723804 [0001]  schbench[28587/28574]               7.935      7.822      0.993      0.000

Signed-off-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Link: https://lore.kernel.org/r/20241004170756.18064-1-vineethr@linux.ibm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

0 files changed, 0 insertions, 0 deletions