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Commit 7c00bafe authored by Tim Chen's avatar Tim Chen Committed by Linus Torvalds
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mm/swap: free swap slots in batch 

Add new functions that free unused swap slots in batches without the
need to reacquire swap info lock.  This improves scalability and reduce
lock contention.

Link: http://lkml.kernel.org/r/c25e0fcdfd237ec4ca7db91631d3b9f6ed23824e.1484082593.git.tim.c.chen@linux.intel.com


Signed-off-by: default avatarTim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net> escreveu:
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 36005bae

include/linux/swap.h

+1 −0
Original line number Diff line number Diff line
@@ -394,6 +394,7 @@ extern int swap_duplicate(swp_entry_t); 
extern int swapcache_prepare(swp_entry_t);

extern void swap_free(swp_entry_t);

extern void swapcache_free(swp_entry_t);

extern void swapcache_free_entries(swp_entry_t *entries, int n);

extern int free_swap_and_cache(swp_entry_t);

extern int swap_type_of(dev_t, sector_t, struct block_device **);

extern unsigned int count_swap_pages(int, int);

mm/swapfile.c

+94 −61
Original line number Diff line number Diff line
@@ -942,34 +942,33 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry) 
	return p;

}



static unsigned char swap_entry_free(struct swap_info_struct *p,

				     swp_entry_t entry, unsigned char usage,

				     bool swap_info_locked)

static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry,

					struct swap_info_struct *q)

{

	struct swap_cluster_info *ci;

	unsigned long offset = swp_offset(entry);

	unsigned char count;

	unsigned char has_cache;

	bool lock_swap_info = false;

	struct swap_info_struct *p;



	if (!swap_info_locked) {

		count = p->swap_map[offset];

		if (!p->cluster_info || count == usage || count == SWAP_MAP_SHMEM) {

lock_swap_info:

			swap_info_locked = true;

			lock_swap_info = true;

	p = _swap_info_get(entry);



	if (p != q) {

		if (q != NULL)

			spin_unlock(&q->lock);

		if (p != NULL)

			spin_lock(&p->lock);

	}

	return p;

}



	ci = lock_cluster(p, offset);

static unsigned char __swap_entry_free(struct swap_info_struct *p,

				       swp_entry_t entry, unsigned char usage)

{

	struct swap_cluster_info *ci;

	unsigned long offset = swp_offset(entry);

	unsigned char count;

	unsigned char has_cache;



	count = p->swap_map[offset];

	ci = lock_cluster_or_swap_info(p, offset);



	if (!swap_info_locked && (count == usage || count == SWAP_MAP_SHMEM)) {

		unlock_cluster(ci);

		goto lock_swap_info;

	}

	count = p->swap_map[offset];



	has_cache = count & SWAP_HAS_CACHE;

	count &= ~SWAP_HAS_CACHE;
@@ -994,21 +993,32 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, 
	}



	usage = count | has_cache;

	p->swap_map[offset] = usage;

	p->swap_map[offset] = usage ? : SWAP_HAS_CACHE;



	unlock_cluster(ci);

	unlock_cluster_or_swap_info(p, ci);



	return usage;

}



static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)

{

	struct swap_cluster_info *ci;

	unsigned long offset = swp_offset(entry);

	unsigned char count;



	/* free if no reference */

	if (!usage) {

		VM_BUG_ON(!swap_info_locked);

		mem_cgroup_uncharge_swap(entry);

	ci = lock_cluster(p, offset);

	count = p->swap_map[offset];

	VM_BUG_ON(count != SWAP_HAS_CACHE);

	p->swap_map[offset] = 0;

	dec_cluster_info_page(p, p->cluster_info, offset);

	unlock_cluster(ci);



	mem_cgroup_uncharge_swap(entry);

	if (offset < p->lowest_bit)

		p->lowest_bit = offset;

	if (offset > p->highest_bit) {

		bool was_full = !p->highest_bit;



		p->highest_bit = offset;

		if (was_full && (p->flags & SWP_WRITEOK)) {

			spin_lock(&swap_avail_lock);
@@ -1024,18 +1034,13 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, 
	frontswap_invalidate_page(p->type, offset);

	if (p->flags & SWP_BLKDEV) {

		struct gendisk *disk = p->bdev->bd_disk;



		if (disk->fops->swap_slot_free_notify)

			disk->fops->swap_slot_free_notify(p->bdev,

							  offset);

	}

}



	if (lock_swap_info)

		spin_unlock(&p->lock);



	return usage;

}



/*

 * Caller has made sure that the swap device corresponding to entry

 * is still around or has not been recycled.
@@ -1045,8 +1050,10 @@ void swap_free(swp_entry_t entry) 
	struct swap_info_struct *p;



	p = _swap_info_get(entry);

	if (p)

		swap_entry_free(p, entry, 1, false);

	if (p) {

		if (!__swap_entry_free(p, entry, 1))

			swapcache_free_entries(&entry, 1);

	}

}



/*
@@ -1057,8 +1064,32 @@ void swapcache_free(swp_entry_t entry) 
	struct swap_info_struct *p;



	p = _swap_info_get(entry);

	if (p) {

		if (!__swap_entry_free(p, entry, SWAP_HAS_CACHE))

			swapcache_free_entries(&entry, 1);

	}

}



void swapcache_free_entries(swp_entry_t *entries, int n)

{

	struct swap_info_struct *p, *prev;

	int i;



	if (n <= 0)

		return;



	prev = NULL;

	p = NULL;

	for (i = 0; i < n; ++i) {

		p = swap_info_get_cont(entries[i], prev);

		if (p)

		swap_entry_free(p, entry, SWAP_HAS_CACHE, false);

			swap_entry_free(p, entries[i]);

		else

			break;

		prev = p;

	}

	if (p)

		spin_unlock(&p->lock);

}



/*
@@ -1241,21 +1272,23 @@ int free_swap_and_cache(swp_entry_t entry) 
{

	struct swap_info_struct *p;

	struct page *page = NULL;

	unsigned char count;



	if (non_swap_entry(entry))

		return 1;



	p = swap_info_get(entry);

	p = _swap_info_get(entry);

	if (p) {

		if (swap_entry_free(p, entry, 1, true) == SWAP_HAS_CACHE) {

		count = __swap_entry_free(p, entry, 1);

		if (count == SWAP_HAS_CACHE) {

			page = find_get_page(swap_address_space(entry),

					     swp_offset(entry));

			if (page && !trylock_page(page)) {

				put_page(page);

				page = NULL;

			}

		}

		spin_unlock(&p->lock);

		} else if (!count)

			swapcache_free_entries(&entry, 1);

	}

	if (page) {

		/*