[patch] oom: add verbose_oom sysctl to dump tasklist

[patch] oom: add verbose_oom sysctl to dump tasklist

[David Rientjes]

Adds 'verbose_oom' sysctl to dump the tasklist and pertinent memory usage
information on an OOM killing.  Information included is pid, uid, tgid,
VM size, RSS, last cpu, oom_adj score, and name.

Cc: Andrea Arcangeli <andrea@suse.de>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 Applied on top of the OOM killer patchset posted to linux-mm by
 Andrea Arcangeli on August 22, 2007.

 Documentation/sysctl/vm.txt |   13 +++++++++++++
 include/linux/sysctl.h      |    1 +
 kernel/sysctl.c             |    9 +++++++++
 mm/oom_kill.c               |   26 ++++++++++++++++++++++++++
 4 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -31,6 +31,7 @@ Currently, these files are in /proc/sys/vm:
 - min_unmapped_ratio
 - min_slab_ratio
 - panic_on_oom
+- verbose_oom
 - mmap_min_address
 - numa_zonelist_order
 
@@ -222,6 +223,18 @@ according to your policy of failover.
 
 ==============================================================
 
+verbose_oom
+
+This enables or disables extra verbosity of the OOM killer.
+
+If this is set to non-zero, the tasklist will be printed along with
+various information about each task such as pid, uid, tgid, VM size, RSS,
+last cpu, oom_adj score, and its name.
+
+The default value is 0.
+
+==============================================================
+
 mmap_min_addr
 
 This file indicates the amount of address space  which a user process will
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -207,6 +207,7 @@ enum
 	VM_PANIC_ON_OOM=33,	/* panic at out-of-memory */
 	VM_VDSO_ENABLED=34,	/* map VDSO into new processes? */
 	VM_MIN_SLAB=35,		 /* Percent pages ignored by zone reclaim */
+	VM_VERBOSE_OOM=36,	/* OOM killer verbosity */
 
 	/* s390 vm cmm sysctls */
 	VM_CMM_PAGES=1111,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -63,6 +63,7 @@ extern int print_fatal_signals;
 extern int sysctl_overcommit_memory;
 extern int sysctl_overcommit_ratio;
 extern int sysctl_panic_on_oom;
+extern int sysctl_verbose_oom;
 extern int max_threads;
 extern int core_uses_pid;
 extern int suid_dumpable;
@@ -790,6 +791,14 @@ static ctl_table vm_table[] = {
 		.proc_handler	= &proc_dointvec,
 	},
 	{
+		.ctl_name	= VM_VERBOSE_OOM,
+		.procname	= "verbose_oom",
+		.data		= &sysctl_verbose_oom,
+		.maxlen		= sizeof(sysctl_verbose_oom),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+	{
 		.ctl_name	= VM_OVERCOMMIT_RATIO,
 		.procname	= "overcommit_ratio",
 		.data		= &sysctl_overcommit_ratio,
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -27,6 +27,7 @@
 #include <linux/notifier.h>
 
 int sysctl_panic_on_oom;
+int sysctl_verbose_oom;
 /* #define DEBUG */
 
 unsigned long VM_is_OOM;
@@ -146,6 +147,29 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
 	return points;
 }
 
+static inline void dump_tasks(void)
+{
+	struct task_struct *g, *p;
+
+	printk(KERN_INFO "[ pid ]   uid  tgid total_vm      rss cpu oom_adj name\n");
+	do_each_thread(g, p) {
+		/*
+		 * total_vm and rss sizes do not exist for tasks with a
+		 * detached mm so there's no need to report them.  They are
+		 * not eligible for OOM killing anyway.
+		 */
+		if (!p->mm)
+			continue;
+
+		task_lock(p);
+		printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d     %3d %s\n",
+		       p->pid, p->uid, p->tgid, p->mm->total_vm,
+		       get_mm_rss(p->mm), (int)task_cpu(p), p->oomkilladj,
+		       p->comm);
+		task_unlock(p);
+	} while_each_thread(g, p);
+}
+
 /*
  * Types of limitations to the nodes from which allocations may occur
  */
@@ -250,6 +274,8 @@ static void __oom_kill_task(struct task_struct *p, int verbose)
 		return;
 	}
 
+	if (sysctl_verbose_oom)
+		dump_tasks();
 	if (verbose)
 		printk(KERN_ERR "Killed process %d (%s)\n", p->pid, p->comm);
 

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Re: [patch] oom: add verbose_oom sysctl to dump tasklist

[Andrew Morton]

On Fri, 7 Sep 2007 01:17:27 -0700 (PDT)
David Rientjes <rientjes@google.com> wrote:

> Adds 'verbose_oom' sysctl to dump the tasklist and pertinent memory usage
> information on an OOM killing.  Information included is pid, uid, tgid,
> VM size, RSS, last cpu, oom_adj score, and name.

Would be useful to have some description of why this is needed, how we will
use it to fix stuff, etc.  IOW: what value does it bring??

And if it _is_ valuable, how come it's tunable offable?  I guess the
tasklist dump will be pretty huge..

We should be dumping more stuff at oom-time.  I thought we were dumping the
sysrq-m-style output but that patch which did that got lost years ago.


> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -207,6 +207,7 @@ enum
>  	VM_PANIC_ON_OOM=33,	/* panic at out-of-memory */
>  	VM_VDSO_ENABLED=34,	/* map VDSO into new processes? */
>  	VM_MIN_SLAB=35,		 /* Percent pages ignored by zone reclaim */
> +	VM_VERBOSE_OOM=36,	/* OOM killer verbosity */
>  
>  	/* s390 vm cmm sysctls */
>  	VM_CMM_PAGES=1111,
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -63,6 +63,7 @@ extern int print_fatal_signals;
>  extern int sysctl_overcommit_memory;
>  extern int sysctl_overcommit_ratio;
>  extern int sysctl_panic_on_oom;
> +extern int sysctl_verbose_oom;
>  extern int max_threads;
>  extern int core_uses_pid;
>  extern int suid_dumpable;
> @@ -790,6 +791,14 @@ static ctl_table vm_table[] = {
>  		.proc_handler	= &proc_dointvec,
>  	},
>  	{
> +		.ctl_name	= VM_VERBOSE_OOM,

We've stopped adding new sysctl numbers: this should use CTL_UNNUMBERED. 
See the nice comment at the end of this array...

> +		.procname	= "verbose_oom",
> +		.data		= &sysctl_verbose_oom,
> +		.maxlen		= sizeof(sysctl_verbose_oom),
> +		.mode		= 0644,
> +		.proc_handler	= &proc_dointvec,
> +	},
> +	{
>  		.ctl_name	= VM_OVERCOMMIT_RATIO,
>  		.procname	= "overcommit_ratio",
>  		.data		= &sysctl_overcommit_ratio,
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -27,6 +27,7 @@
>  #include <linux/notifier.h>
>  
>  int sysctl_panic_on_oom;
> +int sysctl_verbose_oom;
>  /* #define DEBUG */
>  
>  unsigned long VM_is_OOM;
> @@ -146,6 +147,29 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
>  	return points;
>  }
>  
> +static inline void dump_tasks(void)
> +{
> +	struct task_struct *g, *p;
> +
> +	printk(KERN_INFO "[ pid ]   uid  tgid total_vm      rss cpu oom_adj name\n");
> +	do_each_thread(g, p) {
> +		/*
> +		 * total_vm and rss sizes do not exist for tasks with a
> +		 * detached mm so there's no need to report them.  They are
> +		 * not eligible for OOM killing anyway.
> +		 */
> +		if (!p->mm)
> +			continue;
> +
> +		task_lock(p);
> +		printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d     %3d %s\n",
> +		       p->pid, p->uid, p->tgid, p->mm->total_vm,
> +		       get_mm_rss(p->mm), (int)task_cpu(p), p->oomkilladj,
> +		       p->comm);
> +		task_unlock(p);
> +	} while_each_thread(g, p);
> +}

There's no need to inline this.

Also, it appears to be 100% generic and useful, so perhaps it should be put
into kernel/something.c and made available to other code.  Probably there's
already code out there which should be converted to a call to this
function?


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Re: [patch] oom: add verbose_oom sysctl to dump tasklist

[David Rientjes]

On Thu, 13 Sep 2007, Andrew Morton wrote:

> > Adds 'verbose_oom' sysctl to dump the tasklist and pertinent memory usage
> > information on an OOM killing.  Information included is pid, uid, tgid,
> > VM size, RSS, last cpu, oom_adj score, and name.
> 
> Would be useful to have some description of why this is needed, how we will
> use it to fix stuff, etc.  IOW: what value does it bring??
> 

I don't think we would use it to fix anything, I think the end user would 
use it to figure out why his or her system was OOM.

Obviously this is also possible to do from userspace, but with more 
trouble in collecting all the information presented here.

> And if it _is_ valuable, how come it's tunable offable?  I guess the
> tasklist dump will be pretty huge..
> 

As a courtesy to SGI and friends who already have enough trouble scanning 
the tasklist because of their super huge machines.

> We should be dumping more stuff at oom-time.  I thought we were dumping the
> sysrq-m-style output but that patch which did that got lost years ago.
> 

I've wondered about a notifier hook to userspace so if the user had 
specified an OOM handling script to be executed before the actual killer 
was invoked, you could collect this information on your own or anything 
else you found pertinent.

> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > --- a/mm/oom_kill.c
> > +++ b/mm/oom_kill.c
> > @@ -27,6 +27,7 @@
> >  #include <linux/notifier.h>
> >  
> >  int sysctl_panic_on_oom;
> > +int sysctl_verbose_oom;
> >  /* #define DEBUG */
> >  
> >  unsigned long VM_is_OOM;
> > @@ -146,6 +147,29 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
> >  	return points;
> >  }
> >  
> > +static inline void dump_tasks(void)
> > +{
> > +	struct task_struct *g, *p;
> > +
> > +	printk(KERN_INFO "[ pid ]   uid  tgid total_vm      rss cpu oom_adj name\n");
> > +	do_each_thread(g, p) {
> > +		/*
> > +		 * total_vm and rss sizes do not exist for tasks with a
> > +		 * detached mm so there's no need to report them.  They are
> > +		 * not eligible for OOM killing anyway.
> > +		 */
> > +		if (!p->mm)
> > +			continue;
> > +
> > +		task_lock(p);
> > +		printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d     %3d %s\n",
> > +		       p->pid, p->uid, p->tgid, p->mm->total_vm,
> > +		       get_mm_rss(p->mm), (int)task_cpu(p), p->oomkilladj,
> > +		       p->comm);
> > +		task_unlock(p);
> > +	} while_each_thread(g, p);
> > +}
> 
> There's no need to inline this.
> 

Ah, gotcha.

> Also, it appears to be 100% generic and useful, so perhaps it should be put
> into kernel/something.c and made available to other code.  Probably there's
> already code out there which should be converted to a call to this
> function?
> 

I'll look into it, thanks for the review.

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