[patch -mm 1/2] mm, oom: add description of struct oom_control

[patch -mm 1/2] mm, oom: add description of struct oom_control

[David Rientjes]

Describe the purpose of struct oom_control and what each member does.

Also make gfp_mask and order const since they are never manipulated or
passed to functions that discard the qualifier.

Signed-off-by: David Rientjes <rientjes@google.com>
---
 include/linux/oom.h | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/include/linux/oom.h b/include/linux/oom.h
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -12,11 +12,25 @@ struct notifier_block;
 struct mem_cgroup;
 struct task_struct;
 
+/*
+ * Details of the page allocation that triggered the oom killer that are used to
+ * determine what should be killed.
+ */
 struct oom_control {
+	/* Used to determine cpuset */
 	struct zonelist *zonelist;
-	nodemask_t	*nodemask;
-	gfp_t		gfp_mask;
-	int		order;
+
+	/* Used to determine mempolicy */
+	nodemask_t *nodemask;
+
+	/* Used to determine cpuset and node locality requirement */
+	const gfp_t gfp_mask;
+
+	/*
+	 * order == -1 means the oom kill is required by sysrq, otherwise only
+	 * for display purposes.
+	 */
+	const int order;
 };
 
 /*

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[patch -mm 2/2] mm, oom: remove unnecessary variable

[David Rientjes]

The "killed" variable in out_of_memory() can be removed since the call to
oom_kill_process() where we should block to allow the process time to
exit is obvious.

Signed-off-by: David Rientjes <rientjes@google.com>
---
 mm/oom_kill.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -645,7 +645,6 @@ bool out_of_memory(struct oom_control *oc)
 	unsigned long freed = 0;
 	unsigned int uninitialized_var(points);
 	enum oom_constraint constraint = CONSTRAINT_NONE;
-	int killed = 0;
 
 	if (oom_killer_disabled)
 		return false;
@@ -653,7 +652,7 @@ bool out_of_memory(struct oom_control *oc)
 	blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
 	if (freed > 0)
 		/* Got some memory back in the last second. */
-		goto out;
+		return true;
 
 	/*
 	 * If current has a pending SIGKILL or is exiting, then automatically
@@ -666,7 +665,7 @@ bool out_of_memory(struct oom_control *oc)
 	if (current->mm &&
 	    (fatal_signal_pending(current) || task_will_free_mem(current))) {
 		mark_oom_victim(current);
-		goto out;
+		return true;
 	}
 
 	/*
@@ -684,7 +683,7 @@ bool out_of_memory(struct oom_control *oc)
 		get_task_struct(current);
 		oom_kill_process(oc, current, 0, totalpages, NULL,
 				 "Out of memory (oom_kill_allocating_task)");
-		goto out;
+		return true;
 	}
 
 	p = select_bad_process(oc, &points, totalpages);
@@ -696,16 +695,12 @@ bool out_of_memory(struct oom_control *oc)
 	if (p && p != (void *)-1UL) {
 		oom_kill_process(oc, p, points, totalpages, NULL,
 				 "Out of memory");
-		killed = 1;
-	}
-out:
-	/*
-	 * Give the killed threads a good chance of exiting before trying to
-	 * allocate memory again.
-	 */
-	if (killed)
+		/*
+		 * Give the killed process a good chance to exit before trying
+		 * to allocate memory again.
+		 */
 		schedule_timeout_killable(1);
-
+	}
 	return true;
 }
 

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Re: [patch -mm 2/2] mm, oom: remove unnecessary variable

[Michal Hocko]

On Tue 14-07-15 16:45:13, David Rientjes wrote:
> The "killed" variable in out_of_memory() can be removed since the call to
> oom_kill_process() where we should block to allow the process time to
> exit is obvious.
> 
> Signed-off-by: David Rientjes <rientjes@google.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  mm/oom_kill.c | 21 ++++++++-------------
>  1 file changed, 8 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -645,7 +645,6 @@ bool out_of_memory(struct oom_control *oc)
>  	unsigned long freed = 0;
>  	unsigned int uninitialized_var(points);
>  	enum oom_constraint constraint = CONSTRAINT_NONE;
> -	int killed = 0;
>  
>  	if (oom_killer_disabled)
>  		return false;
> @@ -653,7 +652,7 @@ bool out_of_memory(struct oom_control *oc)
>  	blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
>  	if (freed > 0)
>  		/* Got some memory back in the last second. */
> -		goto out;
> +		return true;
>  
>  	/*
>  	 * If current has a pending SIGKILL or is exiting, then automatically
> @@ -666,7 +665,7 @@ bool out_of_memory(struct oom_control *oc)
>  	if (current->mm &&
>  	    (fatal_signal_pending(current) || task_will_free_mem(current))) {
>  		mark_oom_victim(current);
> -		goto out;
> +		return true;
>  	}
>  
>  	/*
> @@ -684,7 +683,7 @@ bool out_of_memory(struct oom_control *oc)
>  		get_task_struct(current);
>  		oom_kill_process(oc, current, 0, totalpages, NULL,
>  				 "Out of memory (oom_kill_allocating_task)");
> -		goto out;
> +		return true;
>  	}
>  
>  	p = select_bad_process(oc, &points, totalpages);
> @@ -696,16 +695,12 @@ bool out_of_memory(struct oom_control *oc)
>  	if (p && p != (void *)-1UL) {
>  		oom_kill_process(oc, p, points, totalpages, NULL,
>  				 "Out of memory");
> -		killed = 1;
> -	}
> -out:
> -	/*
> -	 * Give the killed threads a good chance of exiting before trying to
> -	 * allocate memory again.
> -	 */
> -	if (killed)
> +		/*
> +		 * Give the killed process a good chance to exit before trying
> +		 * to allocate memory again.
> +		 */
>  		schedule_timeout_killable(1);
> -
> +	}
>  	return true;
>  }
>  
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-- 
Michal Hocko
SUSE Labs

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