Re: [PATCH 9/12] memcg allocate all page_cgroup at boot

[KAMEZAWA Hiroyuki]

On Wed, 01 Oct 2008 09:33:53 +0530
Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote:

> > +int __meminit init_section_page_cgroup(unsigned long pfn)
> > +{
> > +	struct mem_section *section;
> > +	struct page_cgroup *base, *pc;
> > +	unsigned long table_size;
> > +	int nid, index;
> > +
> > +	section = __pfn_to_section(pfn);
> > +
> > +	if (section->page_cgroup)
> > +		return 0;
> > +
> > +	nid = page_to_nid(pfn_to_page(pfn));
> > +
> > +	table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
> > +	base = kmalloc_node(table_size, GFP_KERNEL, nid);
> > +	if (!base)
> > +		base = vmalloc_node(table_size, nid);
> 
> Should we check for slab_is_available() before calling kmalloc_node? Otherwise,
> we might need to fallback to alloc_bootmem_node.
> 
That check is not necessary.
Because we use kmalloc()/vmalloc()  in mem_cgroup_create(), after this.

(We assume usual page allocateor is available here. For FLATMEM, size of 
 array can be too big for kmalloc(), etc... I use alloc_bootmem().

> > +
> > +	if (!base) {
> > +		printk("page cgroup allocation failure\n");
> > +		return -ENOMEM;
> > +	}
> > +
> > +	for (index = 0; index < PAGES_PER_SECTION; index++) {
> > +		pc = base + index;
> > +		__init_page_cgroup(pc, pfn + index);
> > +	}
> > +
> > +	section = __pfn_to_section(pfn);
> > +	section->page_cgroup = base - pfn;
> > +	total_usage += table_size;
> > +	return 0;
> > +}
> > +#ifdef CONFIG_MEMORY_HOTPLUG
> > +void __free_page_cgroup(unsigned long pfn)
> > +{
> > +	struct mem_section *ms;
> > +	struct page_cgroup *base;
> > +
> > +	ms = __pfn_to_section(pfn);
> > +	if (!ms || !ms->page_cgroup)
> > +		return;
> > +	base = ms->page_cgroup + pfn;
> > +	ms->page_cgroup = NULL;
> > +	if (is_vmalloc_addr(base))
> > +		vfree(base);
> > +	else
> > +		kfree(base);
> > +}
> > +
> > +int online_page_cgroup(unsigned long start_pfn,
> > +			unsigned long nr_pages,
> > +			int nid)
> > +{
> > +	unsigned long start, end, pfn;
> > +	int fail = 0;
> > +
> > +	start = start_pfn & (PAGES_PER_SECTION - 1);
> > +	end = ALIGN(start_pfn + nr_pages, PAGES_PER_SECTION);
> > +
> > +	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
> > +		if (!pfn_present(pfn))
> > +			continue;
> > +		fail = init_section_page_cgroup(pfn);
> > +	}
> > +	if (!fail)
> > +		return 0;
> > +
> > +	/* rollback */
> > +	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
> > +		__free_page_cgroup(pfn);
> > +
> > +	return -ENOMEM;
> > +}
> > +
> > +int offline_page_cgroup(unsigned long start_pfn,
> > +		unsigned long nr_pages, int nid)
> > +{
> > +	unsigned long start, end, pfn;
> > +
> > +	start = start_pfn & (PAGES_PER_SECTION - 1);
> > +	end = ALIGN(start_pfn + nr_pages, PAGES_PER_SECTION);
> > +
> > +	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
> > +                __free_page_cgroup(pfn);
> > +	return 0;
> > +
> > +}
> > +
> > +static int page_cgroup_callback(struct notifier_block *self,
> > +			       unsigned long action, void *arg)
> > +{
> > +	struct memory_notify *mn = arg;
> > +	int ret = 0;
> > +	switch (action) {
> > +	case MEM_GOING_ONLINE:
> > +		ret = online_page_cgroup(mn->start_pfn,
> > +				   mn->nr_pages, mn->status_change_nid);
> > +		break;
> > +	case MEM_CANCEL_ONLINE:
> > +	case MEM_OFFLINE:
> > +		offline_page_cgroup(mn->start_pfn,
> > +				mn->nr_pages, mn->status_change_nid);
> > +		break;
> > +	case MEM_GOING_OFFLINE:
> > +		break;
> > +        case MEM_ONLINE:
> > +	case MEM_CANCEL_OFFLINE:
> > +		break;
> > +	}
> > +	ret = notifier_from_errno(ret);
> > +	return ret;
> > +}
> > +
> > +#endif
> > +
> > +void __init page_cgroup_init(void)
> > +{
> > +	unsigned long pfn;
> > +	int fail = 0;
> > +
> > +	for (pfn = 0; !fail && pfn < max_pfn; pfn += PAGES_PER_SECTION) {
> > +		if (!pfn_present(pfn))
> > +			continue;
> > +		fail = init_section_page_cgroup(pfn);
> > +	}
> > +	if (fail) {
> > +		printk("please try cgroup_disable=memory boot option\n");
> > +		panic("Out of memory");
> > +	} else {
> > +		hotplug_memory_notifier(page_cgroup_callback, 0);
> > +	}
> > +	printk("allocated %ld bytes of page_cgroup\n", total_usage);
> > +	printk("please try cgroup_disable=memory option if you don't want\n");
> > +}
> > +
> > +void __init pgdat_page_cgroup_init(struct pglist_data *pgdat)
> > +{
> > +	return;
> > +}
> > +
> > +#endif
> 
> I like this code very much, even though I've not tested it. I think it combines
> all we've been thinking and discussing very well (from my initial flatmem based
> code to Dave's suggestion of using mem_section).
> 
> > Index: mmotm-2.6.27-rc7+/include/linux/mm_types.h
> > ===================================================================
> > --- mmotm-2.6.27-rc7+.orig/include/linux/mm_types.h
> > +++ mmotm-2.6.27-rc7+/include/linux/mm_types.h
> > @@ -94,10 +94,6 @@ struct page {
> >  	void *virtual;			/* Kernel virtual address (NULL if
> >  					   not kmapped, ie. highmem) */
> >  #endif /* WANT_PAGE_VIRTUAL */
> > -#ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > -	unsigned long page_cgroup;
> > -#endif
> > -
> 
> Yay! I think we should add some documentation saying, if you think about
> extending struct page, think again, look at how we did it for the memory
> controller (look at memcontrol.c and page_cgroup.c).
> 
???? it's usually not accepted. I've seen such case very much.
I wonder why this was accepted ;)


> >  #ifdef CONFIG_KMEMCHECK
> >  	void *shadow;
> >  #endif
> > Index: mmotm-2.6.27-rc7+/mm/Makefile
> > ===================================================================
> > --- mmotm-2.6.27-rc7+.orig/mm/Makefile
> > +++ mmotm-2.6.27-rc7+/mm/Makefile
> > @@ -34,6 +34,6 @@ obj-$(CONFIG_FS_XIP) += filemap_xip.o
> >  obj-$(CONFIG_MIGRATION) += migrate.o
> >  obj-$(CONFIG_SMP) += allocpercpu.o
> >  obj-$(CONFIG_QUICKLIST) += quicklist.o
> > -obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o
> > +obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
> >  obj-$(CONFIG_CGROUP_MEMRLIMIT_CTLR) += memrlimitcgroup.o
> >  obj-$(CONFIG_KMEMTRACE) += kmemtrace.o
> > Index: mmotm-2.6.27-rc7+/include/linux/page_cgroup.h
> > ===================================================================
> > --- /dev/null
> > +++ mmotm-2.6.27-rc7+/include/linux/page_cgroup.h
> > @@ -0,0 +1,90 @@
> > +#ifndef __LINUX_PAGE_CGROUP_H
> > +#define __LINUX_PAGE_CGROUP_H
> > +#include <linux/bit_spinlock.h>
> > +/*
> > + * Page Cgroup can be considered as an extended mem_map.
> > + * A page_cgroup page is associated with every page descriptor. The
> > + * page_cgroup helps us identify information about the cgroup
> > + * All page cgroups are allocated at boot or memory hotplug event,
> > + * then the page cgroup for pfn always exists.
> > + */
> > +struct page_cgroup {
> > +	unsigned long flags;
> > +	struct mem_cgroup *mem_cgroup;
> > +	struct page *page;
> > +	struct list_head lru;		/* per cgroup LRU list */
> > +};
> > +
> > +void __init pgdat_page_cgroup_init(struct pglist_data *pgdat);
> > +void __init page_cgroup_init(void);
> > +struct page_cgroup *lookup_page_cgroup(struct page *page);
> > +
> > +enum {
> > +	/* flags for mem_cgroup */
> > +	PCG_LOCK,  /* page cgroup is locked */
> > +	PCG_CACHE, /* charged as cache */
> > +	PCG_USED, /* this object is in use. */
> > +	/* flags for LRU placement */
> > +	PCG_ACTIVE, /* page is active in this cgroup */
> > +	PCG_FILE, /* page is file system backed */
> > +	PCG_UNEVICTABLE, /* page is unevictableable */
> > +};
> > +
> > +#define TESTPCGFLAG(uname, lname)			\
> > +static inline int PageCgroup##uname(struct page_cgroup *pc)	\
> > +	{ return test_bit(PCG_##lname, &pc->flags); }
> > +
> > +#define SETPCGFLAG(uname, lname)			\
> > +static inline void SetPageCgroup##uname(struct page_cgroup *pc)\
> > +	{ set_bit(PCG_##lname, &pc->flags);  }
> > +
> > +#define CLEARPCGFLAG(uname, lname)			\
> > +static inline void ClearPageCgroup##uname(struct page_cgroup *pc)	\
> > +	{ clear_bit(PCG_##lname, &pc->flags);  }
> > +
> > +/* Cache flag is set only once (at allocation) */
> > +TESTPCGFLAG(Cache, CACHE)
> > +
> > +TESTPCGFLAG(Used, USED)
> > +CLEARPCGFLAG(Used, USED)
> > +
> > +/* LRU management flags (from global-lru definition) */
> > +TESTPCGFLAG(File, FILE)
> > +SETPCGFLAG(File, FILE)
> > +CLEARPCGFLAG(File, FILE)
> > +
> > +TESTPCGFLAG(Active, ACTIVE)
> > +SETPCGFLAG(Active, ACTIVE)
> > +CLEARPCGFLAG(Active, ACTIVE)
> > +
> > +TESTPCGFLAG(Unevictable, UNEVICTABLE)
> > +SETPCGFLAG(Unevictable, UNEVICTABLE)
> > +CLEARPCGFLAG(Unevictable, UNEVICTABLE)
> > +
> 
> Can we make this patch indepedent of the flags changes and push it in ASAP.
> 
Need much work....Hmm..rewrite all again ? 


> > +static inline int page_cgroup_nid(struct page_cgroup *pc)
> > +{
> > +	return page_to_nid(pc->page);
> > +}
> > +
> > +static inline enum zone_type page_cgroup_zid(struct page_cgroup *pc)
> > +{
> > +	return page_zonenum(pc->page);
> > +}
> > +
> > +static inline void lock_page_cgroup(struct page_cgroup *pc)
> > +{
> > +	bit_spin_lock(PCG_LOCK, &pc->flags);
> > +}
> > +
> > +static inline int trylock_page_cgroup(struct page_cgroup *pc)
> > +{
> > +	return bit_spin_trylock(PCG_LOCK, &pc->flags);
> > +}
> > +
> > +static inline void unlock_page_cgroup(struct page_cgroup *pc)
> > +{
> > +	bit_spin_unlock(PCG_LOCK, &pc->flags);
> > +}
> > +
> > +
> > +#endif
> > Index: mmotm-2.6.27-rc7+/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-2.6.27-rc7+.orig/mm/memcontrol.c
> > +++ mmotm-2.6.27-rc7+/mm/memcontrol.c
> > @@ -35,11 +35,11 @@
> >  #include <linux/vmalloc.h>
> >  #include <linux/mm_inline.h>
> >  #include <linux/writeback.h>
> > +#include <linux/page_cgroup.h>
> > 
> >  #include <asm/uaccess.h>
> > 
> >  struct cgroup_subsys mem_cgroup_subsys __read_mostly;
> > -static struct kmem_cache *page_cgroup_cache __read_mostly;
> >  #define MEM_CGROUP_RECLAIM_RETRIES	5
> > 
> >  /*
> > @@ -139,80 +139,6 @@ static struct mem_cgroup init_mem_cgroup
> > 
> >  #define is_root_cgroup(cgrp)	((cgrp) == &init_mem_cgroup)
> > 
> > -
> > -/*
> > - * We use the lower bit of the page->page_cgroup pointer as a bit spin
> > - * lock.  We need to ensure that page->page_cgroup is at least two
> > - * byte aligned (based on comments from Nick Piggin).  But since
> > - * bit_spin_lock doesn't actually set that lock bit in a non-debug
> > - * uniprocessor kernel, we should avoid setting it here too.
> > - */
> > -#define PAGE_CGROUP_LOCK_BIT 	0x0
> > -#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
> > -#define PAGE_CGROUP_LOCK 	(1 << PAGE_CGROUP_LOCK_BIT)
> > -#else
> > -#define PAGE_CGROUP_LOCK	0x0
> > -#endif
> > -
> > -/*
> > - * A page_cgroup page is associated with every page descriptor. The
> > - * page_cgroup helps us identify information about the cgroup
> > - */
> > -struct page_cgroup {
> > -	struct list_head lru;		/* per cgroup LRU list */
> > -	struct page *page;
> > -	struct mem_cgroup *mem_cgroup;
> > -	unsigned long flags;
> > -};
> > -
> > -enum {
> > -	/* flags for mem_cgroup */
> > -	PCG_CACHE, /* charged as cache */
> > -	/* flags for LRU placement */
> > -	PCG_ACTIVE, /* page is active in this cgroup */
> > -	PCG_FILE, /* page is file system backed */
> > -	PCG_UNEVICTABLE, /* page is unevictableable */
> > -};
> > -
> > -#define TESTPCGFLAG(uname, lname)			\
> > -static inline int PageCgroup##uname(struct page_cgroup *pc)	\
> > -	{ return test_bit(PCG_##lname, &pc->flags); }
> > -
> > -#define SETPCGFLAG(uname, lname)			\
> > -static inline void SetPageCgroup##uname(struct page_cgroup *pc)\
> > -	{ set_bit(PCG_##lname, &pc->flags);  }
> > -
> > -#define CLEARPCGFLAG(uname, lname)			\
> > -static inline void ClearPageCgroup##uname(struct page_cgroup *pc)	\
> > -	{ clear_bit(PCG_##lname, &pc->flags);  }
> > -
> > -
> > -/* Cache flag is set only once (at allocation) */
> > -TESTPCGFLAG(Cache, CACHE)
> > -
> > -/* LRU management flags (from global-lru definition) */
> > -TESTPCGFLAG(File, FILE)
> > -SETPCGFLAG(File, FILE)
> > -CLEARPCGFLAG(File, FILE)
> > -
> > -TESTPCGFLAG(Active, ACTIVE)
> > -SETPCGFLAG(Active, ACTIVE)
> > -CLEARPCGFLAG(Active, ACTIVE)
> > -
> > -TESTPCGFLAG(Unevictable, UNEVICTABLE)
> > -SETPCGFLAG(Unevictable, UNEVICTABLE)
> > -CLEARPCGFLAG(Unevictable, UNEVICTABLE)
> > -
> > -static int page_cgroup_nid(struct page_cgroup *pc)
> > -{
> > -	return page_to_nid(pc->page);
> > -}
> > -
> > -static enum zone_type page_cgroup_zid(struct page_cgroup *pc)
> > -{
> > -	return page_zonenum(pc->page);
> > -}
> > -
> >  enum charge_type {
> >  	MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
> >  	MEM_CGROUP_CHARGE_TYPE_MAPPED,
> > @@ -223,9 +149,9 @@ enum charge_type {
> > 
> >  static const unsigned long
> >  pcg_default_flags[NR_CHARGE_TYPE] = {
> > -	((1 << PCG_CACHE) | (1 << PCG_FILE)),
> > -	((1 << PCG_ACTIVE)),
> > -	((1 << PCG_ACTIVE) | (1 << PCG_CACHE)),
> > +	(1 << PCG_CACHE) | (1 << PCG_FILE) | (1 << PCG_USED) | (1 << PCG_LOCK),
> > +	(1 << PCG_ACTIVE) | (1 << PCG_LOCK) | (1 << PCG_USED),
> > +	(1 << PCG_ACTIVE) | (1 << PCG_CACHE) | (1 << PCG_USED)|  (1 << PCG_LOCK),
> >  	0,
> >  };
> > 
> > @@ -308,37 +234,6 @@ struct mem_cgroup *mem_cgroup_from_task(
> >  				struct mem_cgroup, css);
> >  }
> > 
> > -static inline int page_cgroup_locked(struct page *page)
> > -{
> > -	return bit_spin_is_locked(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
> > -}
> > -
> > -static void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
> > -{
> > -	VM_BUG_ON(!page_cgroup_locked(page));
> > -	page->page_cgroup = ((unsigned long)pc | PAGE_CGROUP_LOCK);
> > -}
> > -
> > -struct page_cgroup *page_get_page_cgroup(struct page *page)
> > -{
> > -	return (struct page_cgroup *) (page->page_cgroup & ~PAGE_CGROUP_LOCK);
> > -}
> > -
> > -static void lock_page_cgroup(struct page *page)
> > -{
> > -	bit_spin_lock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
> > -}
> > -
> > -static int try_lock_page_cgroup(struct page *page)
> > -{
> > -	return bit_spin_trylock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
> > -}
> > -
> > -static void unlock_page_cgroup(struct page *page)
> > -{
> > -	bit_spin_unlock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
> > -}
> > -
> >  static void __mem_cgroup_remove_list(struct mem_cgroup_per_zone *mz,
> >  			struct page_cgroup *pc)
> >  {
> > @@ -442,22 +337,19 @@ void mem_cgroup_move_lists(struct page *
> >  	 * safely get to page_cgroup without it, so just try_lock it:
> >  	 * mem_cgroup_isolate_pages allows for page left on wrong list.
> >  	 */
> > -	if (!try_lock_page_cgroup(page))
> > +	pc = lookup_page_cgroup(page);
> > +
> > +	if (!trylock_page_cgroup(pc))
> >  		return;
> > 
> > -	pc = page_get_page_cgroup(page);
> > -	if (pc) {
> > +	if (PageCgroupUsed(pc)) {
> >  		mem = pc->mem_cgroup;
> >  		mz = page_cgroup_zoneinfo(pc);
> >  		spin_lock_irqsave(&mz->lru_lock, flags);
> > -		/*
> > -		 * check against the race with move_account.
> > -		 */
> > -		if (likely(mem == pc->mem_cgroup))
> > -			__mem_cgroup_move_lists(pc, lru);
> > +		__mem_cgroup_move_lists(pc, lru);
> >  		spin_unlock_irqrestore(&mz->lru_lock, flags);
> >  	}
> > -	unlock_page_cgroup(page);
> > +	unlock_page_cgroup(pc);
> >  }
> > 
> >  /*
> > @@ -544,6 +436,8 @@ unsigned long mem_cgroup_isolate_pages(u
> >  	list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
> >  		if (scan >= nr_to_scan)
> >  			break;
> > +		if (unlikely(!PageCgroupUsed(pc)))
> > +			continue;
> >  		page = pc->page;
> > 
> >  		if (unlikely(!PageLRU(page)))
> > @@ -611,12 +505,12 @@ int mem_cgroup_move_account(struct page 
> >  		/* Now, we assume no_limit...no failure here. */
> >  		return ret;
> >  	}
> > -	if (!try_lock_page_cgroup(page)) {
> > +	if (!trylock_page_cgroup(pc)) {
> >  		res_counter_uncharge(&to->res, PAGE_SIZE);
> >  		return ret;
> >  	}
> > 
> > -	if (page_get_page_cgroup(page) != pc) {
> > +	if (!PageCgroupUsed(pc)) {
> >  		res_counter_uncharge(&to->res, PAGE_SIZE);
> >  		goto out;
> >  	}
> > @@ -634,7 +528,7 @@ int mem_cgroup_move_account(struct page 
> >  		res_counter_uncharge(&to->res, PAGE_SIZE);
> >  	}
> >  out:
> > -	unlock_page_cgroup(page);
> > +	unlock_page_cgroup(pc);
> > 
> >  	return ret;
> >  }
> > @@ -651,26 +545,27 @@ static int mem_cgroup_charge_common(stru
> >  {
> >  	struct mem_cgroup *mem;
> >  	struct page_cgroup *pc;
> > -	unsigned long flags;
> >  	unsigned long nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> >  	struct mem_cgroup_per_zone *mz;
> > +	unsigned long flags;
> > 
> > -	pc = kmem_cache_alloc(page_cgroup_cache, gfp_mask);
> > -	if (unlikely(pc == NULL))
> > -		goto err;
> > -
> > +	pc = lookup_page_cgroup(page);
> > +	/* can happen at boot */
> > +	if (unlikely(!pc))
> > +		return 0;
> > +	prefetchw(pc);
> >  	/*
> >  	 * We always charge the cgroup the mm_struct belongs to.
> >  	 * The mm_struct's mem_cgroup changes on task migration if the
> >  	 * thread group leader migrates. It's possible that mm is not
> >  	 * set, if so charge the init_mm (happens for pagecache usage).
> >  	 */
> > +
> >  	if (likely(!memcg)) {
> >  		rcu_read_lock();
> >  		mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
> >  		if (unlikely(!mem)) {
> >  			rcu_read_unlock();
> > -			kmem_cache_free(page_cgroup_cache, pc);
> >  			return 0;
> >  		}
> >  		/*
> > @@ -706,36 +601,34 @@ static int mem_cgroup_charge_common(stru
> >  		}
> >  	}
> > 
> > +	preempt_disable();
> 
> I don't understand the preempt_disable() is it for atomic operations? I would
> like to split the removal of struct page from atomic operations for performance.
> I think it will make it easier to merge/review.
> 
Memory hotremoval is not related to this.

This preempt_disable() is avoidance for deadlock. (I thought)

 lock_page_cgroup();
	-> spin_lock_irqsave(&mz->lru_lock);
	-> spin_unlock_irqrestore(&mz->lru_lock);
 unlock_page_cgroup();

After review, my current code drops this preempt_disable().



> > +	lock_page_cgroup(pc);
> > +	if (unlikely(PageCgroupUsed(pc))) {
> > +		unlock_page_cgroup(pc);
> > +		res_counter_uncharge(&mem->res, PAGE_SIZE);
> > +		css_put(&mem->css);
> > +		preempt_enable();
> > +		goto done;
> > +	}
> >  	pc->mem_cgroup = mem;
> > -	pc->page = page;
> >  	/*
> >  	 * If a page is accounted as a page cache, insert to inactive list.
> >  	 * If anon, insert to active list.
> >  	 */
> >  	pc->flags = pcg_default_flags[ctype];
> > 
> > -	lock_page_cgroup(page);
> > -	if (unlikely(page_get_page_cgroup(page))) {
> > -		unlock_page_cgroup(page);
> > -		res_counter_uncharge(&mem->res, PAGE_SIZE);
> > -		css_put(&mem->css);
> > -		kmem_cache_free(page_cgroup_cache, pc);
> > -		goto done;
> > -	}
> > -	page_assign_page_cgroup(page, pc);
> > -
> >  	mz = page_cgroup_zoneinfo(pc);
> > +
> >  	spin_lock_irqsave(&mz->lru_lock, flags);
> >  	__mem_cgroup_add_list(mz, pc);
> >  	spin_unlock_irqrestore(&mz->lru_lock, flags);
> > +	unlock_page_cgroup(pc);
> > +	preempt_enable();
> > 
> > -	unlock_page_cgroup(page);
> >  done:
> >  	return 0;
> >  out:
> >  	css_put(&mem->css);
> > -	kmem_cache_free(page_cgroup_cache, pc);
> > -err:
> >  	return -ENOMEM;
> >  }
> > 
> > @@ -743,7 +636,8 @@ int mem_cgroup_charge(struct page *page,
> >  {
> >  	if (mem_cgroup_subsys.disabled)
> >  		return 0;
> > -
> > +	if (PageCompound(page))
> > +		return 0;
> >  	/*
> >  	 * If already mapped, we don't have to account.
> >  	 * If page cache, page->mapping has address_space.
> > @@ -764,7 +658,8 @@ int mem_cgroup_cache_charge(struct page 
> >  {
> >  	if (mem_cgroup_subsys.disabled)
> >  		return 0;
> > -
> > +	if (PageCompound(page))
> > +		return 0;
> >  	/*
> >  	 * Corner case handling. This is called from add_to_page_cache()
> >  	 * in usual. But some FS (shmem) precharges this page before calling it
> > @@ -777,15 +672,16 @@ int mem_cgroup_cache_charge(struct page 
> >  	if (!(gfp_mask & __GFP_WAIT)) {
> >  		struct page_cgroup *pc;
> > 
> > -		lock_page_cgroup(page);
> > -		pc = page_get_page_cgroup(page);
> > -		if (pc) {
> > -			VM_BUG_ON(pc->page != page);
> > -			VM_BUG_ON(!pc->mem_cgroup);
> > -			unlock_page_cgroup(page);
> > +
> > +		pc = lookup_page_cgroup(page);
> > +		if (!pc)
> > +			return 0;
> > +		lock_page_cgroup(pc);
> > +		if (PageCgroupUsed(pc)) {
> > +			unlock_page_cgroup(pc);
> >  			return 0;
> >  		}
> > -		unlock_page_cgroup(page);
> > +		unlock_page_cgroup(pc);
> >  	}
> > 
> >  	if (unlikely(!mm))
> > @@ -812,49 +708,41 @@ __mem_cgroup_uncharge_common(struct page
> > 
> >  	if (mem_cgroup_subsys.disabled)
> >  		return;
> > +	/* check the condition we can know from page */
> > 
> > -	/*
> > -	 * Check if our page_cgroup is valid
> > -	 */
> > -	lock_page_cgroup(page);
> > -	pc = page_get_page_cgroup(page);
> > -	if (unlikely(!pc))
> > -		goto unlock;
> > -
> > -	VM_BUG_ON(pc->page != page);
> > +	pc = lookup_page_cgroup(page);
> > +	if (unlikely(!pc || !PageCgroupUsed(pc)))
> > +		return;
> > +	preempt_disable();
> > +	lock_page_cgroup(pc);
> > +	if (unlikely(page_mapped(page))) {
> > +		unlock_page_cgroup(pc);
> > +		preempt_enable();
> > +		return;
> > +	}
> > +	ClearPageCgroupUsed(pc);
> > +	unlock_page_cgroup(pc);
> > 
> > -	if ((ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
> > -	    && ((PageCgroupCache(pc) || page_mapped(page))))
> > -		goto unlock;
> > -retry:
> >  	mem = pc->mem_cgroup;
> >  	mz = page_cgroup_zoneinfo(pc);
> > +
> >  	spin_lock_irqsave(&mz->lru_lock, flags);
> > -	if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED &&
> > -	    unlikely(mem != pc->mem_cgroup)) {
> > -		/* MAPPED account can be done without lock_page().
> > -		   Check race with mem_cgroup_move_account() */
> > -		spin_unlock_irqrestore(&mz->lru_lock, flags);
> > -		goto retry;
> > -	}
> >  	__mem_cgroup_remove_list(mz, pc);
> >  	spin_unlock_irqrestore(&mz->lru_lock, flags);
> > -
> > -	page_assign_page_cgroup(page, NULL);
> > -	unlock_page_cgroup(page);
> > -
> > -
> > -	res_counter_uncharge(&mem->res, PAGE_SIZE);
> > +	pc->mem_cgroup = NULL;
> >  	css_put(&mem->css);
> > +	preempt_enable();
> > +	res_counter_uncharge(&mem->res, PAGE_SIZE);
> > 
> > -	kmem_cache_free(page_cgroup_cache, pc);
> >  	return;
> > -unlock:
> > -	unlock_page_cgroup(page);
> >  }
> > 
> >  void mem_cgroup_uncharge_page(struct page *page)
> >  {
> > +	if (page_mapped(page))
> > +		return;
> > +	if (page->mapping && !PageAnon(page))
> > +		return;
> >  	__mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_MAPPED);
> >  }
> > 
> > @@ -878,9 +766,9 @@ int mem_cgroup_prepare_migration(struct 
> >  	if (mem_cgroup_subsys.disabled)
> >  		return 0;
> > 
> > -	lock_page_cgroup(page);
> > -	pc = page_get_page_cgroup(page);
> > -	if (pc) {
> > +	pc = lookup_page_cgroup(page);
> > +	lock_page_cgroup(pc);
> > +	if (PageCgroupUsed(pc)) {
> >  		mem = pc->mem_cgroup;
> >  		css_get(&mem->css);
> >  		if (PageCgroupCache(pc)) {
> > @@ -890,7 +778,7 @@ int mem_cgroup_prepare_migration(struct 
> >  				ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
> >  		}
> >  	}
> > -	unlock_page_cgroup(page);
> > +	unlock_page_cgroup(pc);
> >  	if (mem) {
> >  		ret = mem_cgroup_charge_common(newpage, NULL, GFP_KERNEL,
> >  			ctype, mem);
> > @@ -997,6 +885,8 @@ static void mem_cgroup_force_empty_list(
> >  	spin_lock_irqsave(&mz->lru_lock, flags);
> >  	list_for_each_entry_safe(pc, tmp, list, lru) {
> >  		page = pc->page;
> > +		if (!PageCgroupUsed(pc))
> > +			continue;
> >  		/* For avoiding race with speculative page cache handling. */
> >  		if (!PageLRU(page) || !get_page_unless_zero(page)) {
> >  			continue;
> > @@ -1270,8 +1160,8 @@ mem_cgroup_create(struct cgroup_subsys *
> >  	int node;
> > 
> >  	if (unlikely((cont->parent) == NULL)) {
> > +		page_cgroup_init();
> >  		mem = &init_mem_cgroup;
> > -		page_cgroup_cache = KMEM_CACHE(page_cgroup, SLAB_PANIC);
> >  	} else {
> >  		mem = mem_cgroup_alloc();
> >  		if (!mem)
> > Index: mmotm-2.6.27-rc7+/mm/page_alloc.c
> > ===================================================================
> > --- mmotm-2.6.27-rc7+.orig/mm/page_alloc.c
> > +++ mmotm-2.6.27-rc7+/mm/page_alloc.c
> > @@ -44,7 +44,7 @@
> >  #include <linux/backing-dev.h>
> >  #include <linux/fault-inject.h>
> >  #include <linux/page-isolation.h>
> > -#include <linux/memcontrol.h>
> > +#include <linux/page_cgroup.h>
> >  #include <linux/debugobjects.h>
> > 
> >  #include <asm/tlbflush.h>
> > @@ -223,17 +223,12 @@ static inline int bad_range(struct zone 
> > 
> >  static void bad_page(struct page *page)
> >  {
> > -	void *pc = page_get_page_cgroup(page);
> > -
> >  	printk(KERN_EMERG "Bad page state in process '%s'\n" KERN_EMERG
> >  		"page:%p flags:0x%0*lx mapping:%p mapcount:%d count:%d\n",
> >  		current->comm, page, (int)(2*sizeof(unsigned long)),
> >  		(unsigned long)page->flags, page->mapping,
> >  		page_mapcount(page), page_count(page));
> > -	if (pc) {
> > -		printk(KERN_EMERG "cgroup:%p\n", pc);
> > -		page_reset_bad_cgroup(page);
> > -	}
> > +
> >  	printk(KERN_EMERG "Trying to fix it up, but a reboot is needed\n"
> >  		KERN_EMERG "Backtrace:\n");
> >  	dump_stack();
> > @@ -472,7 +467,6 @@ static inline void free_pages_check(stru
> >  	free_page_mlock(page);
> >  	if (unlikely(page_mapcount(page) |
> >  		(page->mapping != NULL)  |
> > -		(page_get_page_cgroup(page) != NULL) |
> >  		(page_count(page) != 0)  |
> >  		(page->flags & PAGE_FLAGS_CHECK_AT_FREE)))
> >  		bad_page(page);
> > @@ -609,7 +603,6 @@ static void prep_new_page(struct page *p
> >  {
> >  	if (unlikely(page_mapcount(page) |
> >  		(page->mapping != NULL)  |
> > -		(page_get_page_cgroup(page) != NULL) |
> >  		(page_count(page) != 0)  |
> >  		(page->flags & PAGE_FLAGS_CHECK_AT_PREP)))
> >  		bad_page(page);
> > @@ -3495,6 +3488,7 @@ static void __paginginit free_area_init_
> >  	pgdat->nr_zones = 0;
> >  	init_waitqueue_head(&pgdat->kswapd_wait);
> >  	pgdat->kswapd_max_order = 0;
> > +	pgdat_page_cgroup_init(pgdat);
> >  	
> >  	for (j = 0; j < MAX_NR_ZONES; j++) {
> >  		struct zone *zone = pgdat->node_zones + j;
> > Index: mmotm-2.6.27-rc7+/include/linux/mmzone.h
> > ===================================================================
> > --- mmotm-2.6.27-rc7+.orig/include/linux/mmzone.h
> > +++ mmotm-2.6.27-rc7+/include/linux/mmzone.h
> > @@ -604,6 +604,9 @@ typedef struct pglist_data {
> >  	int nr_zones;
> >  #ifdef CONFIG_FLAT_NODE_MEM_MAP
> >  	struct page *node_mem_map;
> > +#ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > +	struct page_cgroup *node_page_cgroup;
> > +#endif
> >  #endif
> >  	struct bootmem_data *bdata;
> >  #ifdef CONFIG_MEMORY_HOTPLUG
> > @@ -932,6 +935,7 @@ static inline unsigned long early_pfn_to
> >  #endif
> > 
> >  struct page;
> > +struct page_cgroup;
> >  struct mem_section {
> >  	/*
> >  	 * This is, logically, a pointer to an array of struct
> > @@ -949,6 +953,11 @@ struct mem_section {
> > 
> >  	/* See declaration of similar field in struct zone */
> >  	unsigned long *pageblock_flags;
> > +#ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > +	/* see page_cgroup.h */
> > +	struct page_cgroup *page_cgroup;
> > +	unsigned long pad;
> > +#endif
> >  };
> > 
> >  #ifdef CONFIG_SPARSEMEM_EXTREME
> > Index: mmotm-2.6.27-rc7+/include/linux/memcontrol.h
> > ===================================================================
> > --- mmotm-2.6.27-rc7+.orig/include/linux/memcontrol.h
> > +++ mmotm-2.6.27-rc7+/include/linux/memcontrol.h
> > @@ -29,7 +29,6 @@ struct mm_struct;
> > 
> >  #define page_reset_bad_cgroup(page)	((page)->page_cgroup = 0)
> > 
> > -extern struct page_cgroup *page_get_page_cgroup(struct page *page);
> >  extern int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
> >  				gfp_t gfp_mask);
> >  extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> > @@ -72,16 +71,8 @@ extern void mem_cgroup_record_reclaim_pr
> >  extern long mem_cgroup_calc_reclaim(struct mem_cgroup *mem, struct zone *zone,
> >  					int priority, enum lru_list lru);
> > 
> > -#else /* CONFIG_CGROUP_MEM_RES_CTLR */
> > -static inline void page_reset_bad_cgroup(struct page *page)
> > -{
> > -}
> > -
> > -static inline struct page_cgroup *page_get_page_cgroup(struct page *page)
> > -{
> > -	return NULL;
> > -}
> > 
> > +#else /* CONFIG_CGROUP_MEM_RES_CTLR */
> >  static inline int mem_cgroup_charge(struct page *page,
> >  					struct mm_struct *mm, gfp_t gfp_mask)
> >  {
> > 
> 
> Except for the the performance changes for atomic operations, I like this patch
> very much.
> 
Did you see performance regression by atomic ops ?

I'll rewrite the whole stack from now for your request. 

Thanks,
-Kame

> For the page removal portions
> Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> as a co-maintainer
> 
> 
> -- 
> 	Balbir
> 

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