Re: [RFC][ only for review ] memory controller bacground reclaim [5/5]

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

KAMEZAWA Hiroyuki wrote:
> Create a daemon which does background page reclaim.
> 
> This daemon
>   * starts when usage > high_watermark
>   * stops when usage < low_watermark.
> 
> Because kthread_run() cannot be used when init_mem_cgroup is initialized(Sigh),
> thread for init_mem_cgroup is invoked later by initcall.
> 
> Changes from YAMAMOTO-san's version
>  * use kthread instead of workqueue.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> From: YAMAMOTO Takashi <yamamoto-jCdQPDEk3idL9jVzuh4AOg@public.gmane.org>
> 
> 
> 
>  mm/memcontrol.c |   79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 79 insertions(+)
> 
> Index: linux-2.6.24-rc3-mm1/mm/memcontrol.c
> ===================================================================
> --- linux-2.6.24-rc3-mm1.orig/mm/memcontrol.c	2007-11-28 16:44:57.000000000 +0900
> +++ linux-2.6.24-rc3-mm1/mm/memcontrol.c	2007-11-28 17:21:57.000000000 +0900
> @@ -30,6 +30,8 @@
>  #include <linux/spinlock.h>
>  #include <linux/fs.h>
>  #include <linux/seq_file.h>
> +#include <linux/kthread.h>
> +#include <linux/freezer.h>
>  
>  #include <asm/uaccess.h>
>  
> @@ -122,6 +124,13 @@
>  	 */
>  	struct res_counter res;
>  	/*
> +	 * background reclaim
> +	 */
> +	struct {
> +		wait_queue_head_t waitq;
> +		struct task_struct *thread;
> +	} daemon;

Does this HAS to be a struct?

> +	/*
>  	 * Per cgroup active and inactive list, similar to the
>  	 * per zone LRU lists.
>  	 */
> @@ -401,6 +410,17 @@
>  	}
>  }
>  
> +static void
> +mem_cgroup_schedule_reclaim(struct mem_cgroup *mem)
> +{
> +	if (!unlikely(mem->daemon.thread))
> +		return;
> +	if (!waitqueue_active(&mem->daemon.waitq))
> +		return;
> +	wake_up_interruptible(&mem->daemon.waitq);
> +}
> +
> +
>  int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
>  {
>  	int ret;
> @@ -677,6 +697,8 @@
>  			mem_cgroup_out_of_memory(mem, GFP_KERNEL);
>  		goto free_pc;
>  	}
> +	if (res_counter_above_high_watermark(&mem->res))
> +		mem_cgroup_schedule_reclaim(mem);
>  
>  	atomic_set(&pc->ref_cnt, 1);
>  	pc->mem_cgroup = mem;
> @@ -832,6 +854,38 @@
>  }
>  
>  /*
> + * Background page reclaim daeom for memory controller.
> + */
> +
> +static int mem_cgroup_reclaim_daemon(void *data)
> +{
> +	DEFINE_WAIT(wait);
> +	struct mem_cgroup *mem = data;
> +
> +	css_get(&mem->css);

Won't this prevent the css from being removed?

> +	set_freezable();
> +
> +	while (!kthread_should_stop()) {
> +		prepare_to_wait(&mem->daemon.waitq, &wait, TASK_INTERRUPTIBLE);
> +		
> +		if (res_counter_below_low_watermark(&mem->res)) {
> +			if (!kthread_should_stop()) {
> +				schedule();
> +				try_to_freeze();
> +			}
> +			finish_wait(&mem->daemon.waitq, &wait);
> +			continue;
> +		}
> +		finish_wait(&mem->daemon.waitq, &wait);
> +		try_to_free_mem_cgroup_pages(mem, GFP_HIGHUSER_MOVABLE);
> +	}
> +
> +	css_put(&mem->css);
> +	
> +	return 0;
> +}
> +
> +/*
>   * This routine traverse page_cgroup in given list and drop them all.
>   * This routine ignores page_cgroup->ref_cnt.
>   * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
> @@ -1045,6 +1100,7 @@
>  {
>  	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
>  	int ret;
> +

This hunk is not needed :)

>  	ret = mem_cgroup_force_empty(mem);
>  	if (!ret)
>  		ret = nbytes;
> @@ -1188,6 +1244,16 @@
>  
>  static struct mem_cgroup init_mem_cgroup;
>  
> +static int __init mem_cgroup_reclaim_init(void)
> +{
> +	init_mem_cgroup.daemon.thread = kthread_run(mem_cgroup_reclaim_daemon,
> +					&init_mem_cgroup, "memcontd");
> +	if (IS_ERR(init_mem_cgroup.daemon.thread))
> +		BUG();
> +	return 0;
> +}
> +late_initcall(mem_cgroup_reclaim_init);
> +
>  static struct cgroup_subsys_state *
>  mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>  {
> @@ -1212,6 +1278,17 @@
>  		if (alloc_mem_cgroup_per_zone_info(mem, node))
>  			goto free_out;
>  
> +	/* Memory Reclaim Daemon per cgroup */
> +	init_waitqueue_head(&mem->daemon.waitq);
> +	if (mem != &init_mem_cgroup) {
> +		/* Complicated...but we cannot call kthread create here..*/
> +		/* init call will later assign kthread */
> +		mem->daemon.thread = kthread_run(mem_cgroup_reclaim_daemon,
> +					mem, "memcontd");
> +		if (IS_ERR(mem->daemon.thread))
> +			goto free_out;

goto free_mem_cgroup_per_zone_info()?

> +	}
> +
>  	return &mem->css;
>  free_out:
>  	for_each_node_state(node, N_POSSIBLE)
> @@ -1226,6 +1303,7 @@
>  {
>  	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
>  	mem_cgroup_force_empty(mem);
> +	kthread_stop(mem->daemon.thread);
>  }
>  
>  static void mem_cgroup_destroy(struct cgroup_subsys *ss,
> 
>