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tracepoint: add tracepoints for debugging oom_score_adj

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oom_score_adj is used for guarding processes from OOM-Killer.  One of
problem is that it's inherited at fork().  When a daemon set oom_score_adj
and make children, it's hard to know where the value is set.

This patch adds some tracepoints useful for debugging. This patch adds
3 trace points.
  - creating new task
  - renaming a task (exec)
  - set oom_score_adj

To debug, users need to enable some trace pointer. Maybe filtering is useful as

# EVENT=/sys/kernel/debug/tracing/events/task/
# echo "oom_score_adj != 0" > $EVENT/task_newtask/filter
# echo "oom_score_adj != 0" > $EVENT/task_rename/filter
# echo 1 > $EVENT/enable
# EVENT=/sys/kernel/debug/tracing/events/oom/
# echo 1 > $EVENT/enable

output will be like this.
# grep oom /sys/kernel/debug/tracing/trace
bash-7699  [007] d..3  5140.744510: oom_score_adj_update: pid=7699 comm=bash oom_score_adj=-1000
bash-7699  [007] ...1  5151.818022: task_newtask: pid=7729 comm=bash clone_flags=1200011 oom_score_adj=-1000
ls-7729  [003] ...2  5151.818504: task_rename: pid=7729 oldcomm=bash newcomm=ls oom_score_adj=-1000
bash-7699  [002] ...1  5175.701468: task_newtask: pid=7730 comm=bash clone_flags=1200011 oom_score_adj=-1000
grep-7730  [007] ...2  5175.701993: task_rename: pid=7730 oldcomm=bash newcomm=grep oom_score_adj=-1000

Signed-off-by: KAMEZAWA Hiroyuki <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Acked-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
KAMEZAWA Hiroyuki 2012-01-10 15:08:09 -08:00 • committed by Linus Torvalds
commit 43d2b11324
6 changed files with 113 additions and 0 deletions
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4
fs/exec.c
View file

@ -59,6 +59,8 @@
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
#include <trace/events/task.h>
#include "internal.h"
int core_uses_pid;
@ -1054,6 +1056,8 @@ void set_task_comm(struct task_struct *tsk, char *buf)
{
task_lock(tsk);
trace_task_rename(tsk, buf);
/*
* Threads may access current->comm without holding
* the task lock, so write the string carefully.

3
fs/proc/base.c
View file

@ -86,6 +86,7 @@
#ifdef CONFIG_HARDWALL
#include <asm/hardwall.h>
#endif
#include <trace/events/oom.h>
#include "internal.h"
/* NOTE:
@ -1010,6 +1011,7 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
else
task->signal->oom_score_adj = (oom_adjust * OOM_SCORE_ADJ_MAX) /
-OOM_DISABLE;
trace_oom_score_adj_update(task);
err_sighand:
unlock_task_sighand(task, &flags);
err_task_lock:
@ -1097,6 +1099,7 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
task->signal->oom_score_adj = oom_score_adj;
if (has_capability_noaudit(current, CAP_SYS_RESOURCE))
task->signal->oom_score_adj_min = oom_score_adj;
trace_oom_score_adj_update(task);
/*
* Scale /proc/pid/oom_adj appropriately ensuring that OOM_DISABLE is
* always attainable.