Re: [PATCH 24 of 24] add oom_kill_asking_task flag

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 22 Aug 2007 14:49:11 +0200 Andrea Arcangeli <andrea@suse.de> wrote:

> # HG changeset patch
> # User David Rientjes <rientjes@google.com>
> # Date 1187778125 -7200
> # Node ID 96b5899e730ecaa2078883f75e86765fa1a36431
> # Parent  a3d679df54ebb1f977b97ab6b3e501134bf9e7ef
> add oom_kill_asking_task flag
> 
> Adds an oom_kill_asking_task flag to cpusets.  If unset (by default), we
> iterate through the task list via select_bad_process() during a
> cpuset-constrained OOM to find the best candidate task to kill.  If set,
> we simply kill current to avoid the overhead which is needed for some
> customers with a large number of threads or heavy workload.
> 

another sgi prod, please.

> 
> diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
> --- a/Documentation/cpusets.txt
> +++ b/Documentation/cpusets.txt
> @@ -181,6 +181,9 @@ containing the following files describin
>   - tasks: list of tasks (by pid) attached to that cpuset
>   - notify_on_release flag: run /sbin/cpuset_release_agent on exit?
>   - memory_pressure: measure of how much paging pressure in cpuset
> + - oom_kill_asking_task flag: when this cpuset OOM's, should we kill
> +	the task that asked for the memory or should we iterate through
> +	the task list to find the best task to kill (can be expensive)?
>  
>  In addition, the root cpuset only has the following file:
>   - memory_pressure_enabled flag: compute memory_pressure?
> diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
> --- a/include/linux/cpuset.h
> +++ b/include/linux/cpuset.h
> @@ -52,6 +52,7 @@ extern void cpuset_set_last_tif_memdie(s
>  				       unsigned long last_tif_memdie);
>  extern int cpuset_set_oom(struct task_struct *task);
>  extern void cpuset_clear_oom(struct task_struct *task);
> +extern int cpuset_oom_kill_asking_task(struct task_struct *task);
>  
>  #define cpuset_memory_pressure_bump() 				\
>  	do {							\
> @@ -136,6 +137,10 @@ static inline int cpuset_set_oom(struct 
>  	return 0;
>  }
>  static inline void cpuset_clear_oom(struct task_struct *task) {}
> +static inline int cpuset_oom_kill_asking_task(struct task_struct *task)
> +{
> +	return 0;
> +}
>  
>  static inline void cpuset_memory_pressure_bump(void) {}
>  
> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> --- a/kernel/cpuset.c
> +++ b/kernel/cpuset.c
> @@ -116,6 +116,7 @@ typedef enum {
>  	CS_SPREAD_PAGE,
>  	CS_SPREAD_SLAB,
>  	CS_OOM,
> +	CS_OOM_KILL_ASKING_TASK,
>  } cpuset_flagbits_t;
>  
>  /* convenient tests for these bits */
> @@ -157,6 +158,11 @@ static inline int is_oom(const struct cp
>  static inline int is_oom(const struct cpuset *cs)
>  {
>  	return test_bit(CS_OOM, &cs->flags);
> +}
> +
> +static inline int is_oom_kill_asking_task(const struct cpuset *cs)
> +{
> +	return test_bit(CS_OOM_KILL_ASKING_TASK, &cs->flags);
>  }
>  
>  /*
> @@ -1068,7 +1074,8 @@ static int update_memory_pressure_enable
>   * update_flag - read a 0 or a 1 in a file and update associated flag
>   * bit:	the bit to update (CS_CPU_EXCLUSIVE, CS_MEM_EXCLUSIVE,
>   *				CS_NOTIFY_ON_RELEASE, CS_MEMORY_MIGRATE,
> - *				CS_SPREAD_PAGE, CS_SPREAD_SLAB)
> + *				CS_SPREAD_PAGE, CS_SPREAD_SLAB,
> + *				CS_OOM_KILL_ASKING_TASK)
>   * cs:	the cpuset to update
>   * buf:	the buffer where we read the 0 or 1
>   *
> @@ -1320,6 +1327,7 @@ typedef enum {
>  	FILE_NOTIFY_ON_RELEASE,
>  	FILE_MEMORY_PRESSURE_ENABLED,
>  	FILE_MEMORY_PRESSURE,
> +	FILE_OOM_KILL_ASKING_TASK,
>  	FILE_SPREAD_PAGE,
>  	FILE_SPREAD_SLAB,
>  	FILE_TASKLIST,
> @@ -1382,6 +1390,9 @@ static ssize_t cpuset_common_file_write(
>  	case FILE_MEMORY_PRESSURE:
>  		retval = -EACCES;
>  		break;
> +	case FILE_OOM_KILL_ASKING_TASK:
> +		retval = update_flag(CS_OOM_KILL_ASKING_TASK, cs, buffer);
> +		break;
>  	case FILE_SPREAD_PAGE:
>  		retval = update_flag(CS_SPREAD_PAGE, cs, buffer);
>  		cs->mems_generation = cpuset_mems_generation++;
> @@ -1499,6 +1510,9 @@ static ssize_t cpuset_common_file_read(s
>  	case FILE_MEMORY_PRESSURE:
>  		s += sprintf(s, "%d", fmeter_getrate(&cs->fmeter));
>  		break;
> +	case FILE_OOM_KILL_ASKING_TASK:
> +		*s++ = is_oom_kill_asking_task(cs) ? '1' : '0';
> +		break;
>  	case FILE_SPREAD_PAGE:
>  		*s++ = is_spread_page(cs) ? '1' : '0';
>  		break;
> @@ -1861,6 +1875,11 @@ static struct cftype cft_memory_pressure
>  static struct cftype cft_memory_pressure = {
>  	.name = "memory_pressure",
>  	.private = FILE_MEMORY_PRESSURE,
> +};
> +
> +static struct cftype cft_oom_kill_asking_task = {
> +	.name = "oom_kill_asking_task",
> +	.private = FILE_OOM_KILL_ASKING_TASK,
>  };
>  
>  static struct cftype cft_spread_page = {
> @@ -1891,6 +1910,8 @@ static int cpuset_populate_dir(struct de
>  		return err;
>  	if ((err = cpuset_add_file(cs_dentry, &cft_memory_pressure)) < 0)
>  		return err;
> +	if ((err = cpuset_add_file(cs_dentry, &cft_oom_kill_asking_task)) < 0)
> +		return err;
>  	if ((err = cpuset_add_file(cs_dentry, &cft_spread_page)) < 0)
>  		return err;
>  	if ((err = cpuset_add_file(cs_dentry, &cft_spread_slab)) < 0)
> @@ -1923,6 +1944,8 @@ static long cpuset_create(struct cpuset 
>  	cs->flags = 0;
>  	if (notify_on_release(parent))
>  		set_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);
> +	if (is_oom_kill_asking_task(parent))
> +		set_bit(CS_OOM_KILL_ASKING_TASK, &cs->flags);
>  	if (is_spread_page(parent))
>  		set_bit(CS_SPREAD_PAGE, &cs->flags);
>  	if (is_spread_slab(parent))
> @@ -2661,6 +2684,20 @@ void cpuset_clear_oom(struct task_struct
>  }
>  
>  /*
> + * Returns 1 if current should simply be killed when a cpuset-constrained OOM
> + * occurs.  Otherwise, we iterate through the task list and select the best
> + * candidate we can find.
> + */
> +int cpuset_oom_kill_asking_task(struct task_struct *task)
> +{
> +	int ret;
> +	task_lock(task);
> +	ret = is_oom_kill_asking_task(task->cpuset);
> +	task_unlock(task);
> +	return ret;
> +}
> +
> +/*
>   * Collection of memory_pressure is suppressed unless
>   * this flag is enabled by writing "1" to the special
>   * cpuset file 'memory_pressure_enabled' in the root cpuset.
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -457,6 +457,13 @@ void out_of_memory(struct zonelist *zone
>  
>  	case CONSTRAINT_CPUSET:
>  		read_lock(&tasklist_lock);
> +		if (cpuset_oom_kill_asking_task(current)) {
> +			oom_kill_process(current, 0,
> +					 "No available memory in cpuset", gfp_mask,
> +					 order);
> +			goto out_cpuset;
> +		}
> +
>  		last_tif_memdie = cpuset_get_last_tif_memdie(current);
>  		/*
>  		 * If current's cpuset is already in the OOM killer or its killed
> 

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