Hi Shaohua,
On Tue, 2013-01-22 at 10:30 +0800, Shaohua Li wrote:
> swap_lock is heavily contended when I test swap to 3 fast SSD (even slightly
> slower than swap to 2 such SSD). The main contention comes from
> swap_info_get(). This patch tries to fix the gap with adding a new
> per-partition lock.
>
> global data like nr_swapfiles, total_swap_pages, least_priority and swap_list are
> still protected by swap_lock.
>
> nr_swap_pages is an atomic now, it can be changed without swap_lock. In theory,
> it's possible get_swap_page() finds no swap pages but actually there are free
> swap pages. But sounds not a big problem.
How can this happen?
>
> accessing partition specific data (like scan_swap_map and so on) is only
> protected by swap_info_struct.lock.
>
> Changing swap_info_struct.flags need hold swap_lock and swap_info_struct.lock,
> because scan_scan_map() will check it. read the flags is ok with either the
> locks hold.
>
> If both swap_lock and swap_info_struct.lock must be hold, we always hold the
> former first to avoid deadlock.
>
> swap_entry_free() can change swap_list. To delete that code, we add a new
> highest_priority_index. Whenever get_swap_page() is called, we check it. If
> it's valid, we use it.
>
> It's a pitty get_swap_page() still holds swap_lock(). But in practice,
> swap_lock() isn't heavily contended in my test with this patch (or I can say
> there are other much more heavier bottlenecks like TLB flush). And BTW, looks
> get_swap_page() doesn't really need the lock. We never free swap_info[] and we
> check SWAP_WRITEOK flag. The only risk without the lock is we could swapout to
> some low priority swap, but we can quickly recover after several rounds of
> swap, so sounds not a big deal to me. But I'd prefer to fix this if it's a real
> problem.
>
> V1->V2: add comments and refresh against latest kernel
>
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
> ---
> drivers/staging/zcache/zcache-main.c | 23 +++--
> include/linux/swap.h | 32 ++++++-
> mm/mmap.c | 2
> mm/swap_state.c | 3
> mm/swapfile.c | 150 ++++++++++++++++++++++++-----------
> mm/vmscan.c | 8 -
> 6 files changed, 157 insertions(+), 61 deletions(-)
>
> Index: linux/include/linux/swap.h
> ===================================================================
> --- linux.orig/include/linux/swap.h 2013-01-22 09:48:23.072725192 +0800
> +++ linux/include/linux/swap.h 2013-01-22 09:50:23.183214092 +0800
> @@ -202,6 +202,18 @@ struct swap_info_struct {
> unsigned long *frontswap_map; /* frontswap in-use, one bit per page */
> atomic_t frontswap_pages; /* frontswap pages in-use counter */
> #endif
> + spinlock_t lock; /*
> + * protect map scan related fields like
> + * swap_map, lowest_bit, highest_bit,
> + * inuse_pages, cluster_next,
> + * cluster_nr, lowest_alloc and
> + * highest_alloc. other fields are only
> + * changed at swapon/swapoff, so are
> + * protected by swap_lock. changing
> + * flags need hold this lock and
> + * swap_lock. If both locks need hold,
> + * hold swap_lock first.
> + */
> };
>
> struct swap_list_t {
> @@ -209,9 +221,6 @@ struct swap_list_t {
> int next; /* swapfile to be used next */
> };
>
> -/* Swap 50% full? Release swapcache more aggressively.. */
> -#define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)
> -
> /* linux/mm/page_alloc.c */
> extern unsigned long totalram_pages;
> extern unsigned long totalreserve_pages;
> @@ -347,8 +356,20 @@ extern struct page *swapin_readahead(swp
> struct vm_area_struct *vma, unsigned long addr);
>
> /* linux/mm/swapfile.c */
> -extern long nr_swap_pages;
> +extern atomic_long_t nr_swap_pages;
> extern long total_swap_pages;
> +
> +/* Swap 50% full? Release swapcache more aggressively.. */
> +static inline bool vm_swap_full(void)
> +{
> + return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
> +}
> +
> +static inline long get_nr_swap_pages(void)
> +{
> + return atomic_long_read(&nr_swap_pages);
> +}
> +
> extern void si_swapinfo(struct sysinfo *);
> extern swp_entry_t get_swap_page(void);
> extern swp_entry_t get_swap_page_of_type(int);
> @@ -381,9 +402,10 @@ mem_cgroup_uncharge_swapcache(struct pag
>
> #else /* CONFIG_SWAP */
>
> -#define nr_swap_pages 0L
> +#define get_nr_swap_pages() 0L
> #define total_swap_pages 0L
> #define total_swapcache_pages() 0UL
> +#define vm_swap_full() 0
>
> #define si_swapinfo(val) \
> do { (val)->freeswap = (val)->totalswap = 0; } while (0)
> Index: linux/mm/swapfile.c
> ===================================================================
> --- linux.orig/mm/swapfile.c 2013-01-22 09:48:23.064725288 +0800
> +++ linux/mm/swapfile.c 2013-01-22 09:48:41.044499432 +0800
> @@ -47,9 +47,11 @@ static sector_t map_swap_entry(swp_entry
>
> DEFINE_SPINLOCK(swap_lock);
> static unsigned int nr_swapfiles;
> -long nr_swap_pages;
> +atomic_long_t nr_swap_pages;
> +/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
> long total_swap_pages;
> static int least_priority;
> +static atomic_t highest_priority_index = ATOMIC_INIT(-1);
>
> static const char Bad_file[] = "Bad swap file entry ";
> static const char Unused_file[] = "Unused swap file entry ";
> @@ -223,7 +225,7 @@ static unsigned long scan_swap_map(struc
> si->lowest_alloc = si->max;
> si->highest_alloc = 0;
> }
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
>
> /*
> * If seek is expensive, start searching for new cluster from
> @@ -242,7 +244,7 @@ static unsigned long scan_swap_map(struc
> if (si->swap_map[offset])
> last_in_cluster = offset + SWAPFILE_CLUSTER;
> else if (offset == last_in_cluster) {
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> offset -= SWAPFILE_CLUSTER - 1;
> si->cluster_next = offset;
> si->cluster_nr = SWAPFILE_CLUSTER - 1;
> @@ -263,7 +265,7 @@ static unsigned long scan_swap_map(struc
> if (si->swap_map[offset])
> last_in_cluster = offset + SWAPFILE_CLUSTER;
> else if (offset == last_in_cluster) {
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> offset -= SWAPFILE_CLUSTER - 1;
> si->cluster_next = offset;
> si->cluster_nr = SWAPFILE_CLUSTER - 1;
> @@ -277,7 +279,7 @@ static unsigned long scan_swap_map(struc
> }
>
> offset = scan_base;
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> si->cluster_nr = SWAPFILE_CLUSTER - 1;
> si->lowest_alloc = 0;
> }
> @@ -293,9 +295,9 @@ checks:
> /* reuse swap entry of cache-only swap if not busy. */
> if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
> int swap_was_freed;
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
> swap_was_freed = __try_to_reclaim_swap(si, offset);
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> /* entry was freed successfully, try to use this again */
> if (swap_was_freed)
> goto checks;
> @@ -335,13 +337,13 @@ checks:
> si->lowest_alloc <= last_in_cluster)
> last_in_cluster = si->lowest_alloc - 1;
> si->flags |= SWP_DISCARDING;
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
>
> if (offset < last_in_cluster)
> discard_swap_cluster(si, offset,
> last_in_cluster - offset + 1);
>
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> si->lowest_alloc = 0;
> si->flags &= ~SWP_DISCARDING;
>
> @@ -355,10 +357,10 @@ checks:
> * could defer that delay until swap_writepage,
> * but it's easier to keep this self-contained.
> */
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
> wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
> wait_for_discard, TASK_UNINTERRUPTIBLE);
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> } else {
> /*
> * Note pages allocated by racing tasks while
> @@ -374,14 +376,14 @@ checks:
> return offset;
>
> scan:
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
> while (++offset <= si->highest_bit) {
> if (!si->swap_map[offset]) {
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> goto checks;
> }
> if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> goto checks;
> }
> if (unlikely(--latency_ration < 0)) {
> @@ -392,11 +394,11 @@ scan:
> offset = si->lowest_bit;
> while (++offset < scan_base) {
> if (!si->swap_map[offset]) {
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> goto checks;
> }
> if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
> goto checks;
> }
> if (unlikely(--latency_ration < 0)) {
> @@ -404,7 +406,7 @@ scan:
> latency_ration = LATENCY_LIMIT;
> }
> }
> - spin_lock(&swap_lock);
> + spin_lock(&si->lock);
>
> no_page:
> si->flags -= SWP_SCANNING;
> @@ -417,13 +419,34 @@ swp_entry_t get_swap_page(void)
> pgoff_t offset;
> int type, next;
> int wrapped = 0;
> + int hp_index;
>
> spin_lock(&swap_lock);
> - if (nr_swap_pages <= 0)
> + if (atomic_long_read(&nr_swap_pages) <= 0)
> goto noswap;
> - nr_swap_pages--;
> + atomic_long_dec(&nr_swap_pages);
>
> for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
> + hp_index = atomic_xchg(&highest_priority_index, -1);
> + /*
> + * highest_priority_index records current highest priority swap
> + * type which just frees swap entries. If its priority is
> + * higher than that of swap_list.next swap type, we use it. It
> + * isn't protected by swap_lock, so it can be an invalid value
> + * if the corresponding swap type is swapoff. We double check
> + * the flags here. It's even possible the swap type is swapoff
> + * and swapon again and its priority is changed. In such rare
> + * case, low prority swap type might be used, but eventually
> + * high priority swap will be used after several rounds of
> + * swap.
> + */
> + if (hp_index != -1 && hp_index != type &&
> + swap_info[type]->prio < swap_info[hp_index]->prio &&
> + (swap_info[hp_index]->flags & SWP_WRITEOK)) {
> + type = hp_index;
> + swap_list.next = type;
> + }
> +
> si = swap_info[type];
> next = si->next;
> if (next < 0 ||
> @@ -432,22 +455,30 @@ swp_entry_t get_swap_page(void)
> wrapped++;
> }
>
> - if (!si->highest_bit)
> + spin_lock(&si->lock);
> + if (!si->highest_bit) {
> + spin_unlock(&si->lock);
> continue;
> - if (!(si->flags & SWP_WRITEOK))
> + }
> + if (!(si->flags & SWP_WRITEOK)) {
> + spin_unlock(&si->lock);
> continue;
> + }
>
> swap_list.next = next;
> +
> + spin_unlock(&swap_lock);
> /* This is called for allocating swap entry for cache */
> offset = scan_swap_map(si, SWAP_HAS_CACHE);
> if (offset) {
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
> return swp_entry(type, offset);
> }
> + spin_lock(&swap_lock);
> next = swap_list.next;
> }
>
> - nr_swap_pages++;
> + atomic_long_inc(&nr_swap_pages);
> noswap:
> spin_unlock(&swap_lock);
> return (swp_entry_t) {0};
> @@ -459,19 +490,19 @@ swp_entry_t get_swap_page_of_type(int ty
> struct swap_info_struct *si;
> pgoff_t offset;
>
> - spin_lock(&swap_lock);
> si = swap_info[type];
> + spin_lock(&si->lock);
> if (si && (si->flags & SWP_WRITEOK)) {
> - nr_swap_pages--;
> + atomic_long_dec(&nr_swap_pages);
> /* This is called for allocating swap entry, not cache */
> offset = scan_swap_map(si, 1);
> if (offset) {
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
> return swp_entry(type, offset);
> }
> - nr_swap_pages++;
> + atomic_long_inc(&nr_swap_pages);
> }
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
> return (swp_entry_t) {0};
> }
>
> @@ -493,7 +524,7 @@ static struct swap_info_struct *swap_inf
> goto bad_offset;
> if (!p->swap_map[offset])
> goto bad_free;
> - spin_lock(&swap_lock);
> + spin_lock(&p->lock);
> return p;
>
> bad_free:
> @@ -511,6 +542,27 @@ out:
> return NULL;
> }
>
> +/*
> + * This swap type frees swap entry, check if it is the highest priority swap
> + * type which just frees swap entry. get_swap_page() uses
> + * highest_priority_index to search highest priority swap type. The
> + * swap_info_struct.lock can't protect us if there are multiple swap types
> + * active, so we use atomic_cmpxchg.
> + */
> +static void set_highest_priority_index(int type)
> +{
> + int old_hp_index, new_hp_index;
> +
> + do {
> + old_hp_index = atomic_read(&highest_priority_index);
> + if (old_hp_index != -1 &&
> + swap_info[old_hp_index]->prio >= swap_info[type]->prio)
> + break;
> + new_hp_index = type;
> + } while (atomic_cmpxchg(&highest_priority_index,
> + old_hp_index, new_hp_index) != old_hp_index);
> +}
> +
> static unsigned char swap_entry_free(struct swap_info_struct *p,
> swp_entry_t entry, unsigned char usage)
> {
> @@ -553,10 +605,8 @@ static unsigned char swap_entry_free(str
> p->lowest_bit = offset;
> if (offset > p->highest_bit)
> p->highest_bit = offset;
> - if (swap_list.next >= 0 &&
> - p->prio > swap_info[swap_list.next]->prio)
> - swap_list.next = p->type;
> - nr_swap_pages++;
> + set_highest_priority_index(p->type);
> + atomic_long_inc(&nr_swap_pages);
> p->inuse_pages--;
> frontswap_invalidate_page(p->type, offset);
> if (p->flags & SWP_BLKDEV) {
> @@ -581,7 +631,7 @@ void swap_free(swp_entry_t entry)
> p = swap_info_get(entry);
> if (p) {
> swap_entry_free(p, entry, 1);
> - spin_unlock(&swap_lock);
> + spin_unlock(&p->lock);
> }
> }
>
> @@ -598,7 +648,7 @@ void swapcache_free(swp_entry_t entry, s
> count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
> if (page)
> mem_cgroup_uncharge_swapcache(page, entry, count != 0);
> - spin_unlock(&swap_lock);
> + spin_unlock(&p->lock);
> }
> }
>
> @@ -617,7 +667,7 @@ int page_swapcount(struct page *page)
> p = swap_info_get(entry);
> if (p) {
> count = swap_count(p->swap_map[swp_offset(entry)]);
> - spin_unlock(&swap_lock);
> + spin_unlock(&p->lock);
> }
> return count;
> }
> @@ -706,7 +756,7 @@ int free_swap_and_cache(swp_entry_t entr
> page = NULL;
> }
> }
> - spin_unlock(&swap_lock);
> + spin_unlock(&p->lock);
> }
> if (page) {
> /*
> @@ -804,11 +854,13 @@ unsigned int count_swap_pages(int type,
> if ((unsigned int)type < nr_swapfiles) {
> struct swap_info_struct *sis = swap_info[type];
>
> + spin_lock(&sis->lock);
> if (sis->flags & SWP_WRITEOK) {
> n = sis->pages;
> if (free)
> n -= sis->inuse_pages;
> }
> + spin_unlock(&sis->lock);
> }
> spin_unlock(&swap_lock);
> return n;
> @@ -1457,7 +1509,7 @@ static void _enable_swap_info(struct swa
> p->swap_map = swap_map;
> frontswap_map_set(p, frontswap_map);
> p->flags |= SWP_WRITEOK;
> - nr_swap_pages += p->pages;
> + atomic_long_add(p->pages, &nr_swap_pages);
> total_swap_pages += p->pages;
>
> /* insert swap space into swap_list: */
> @@ -1479,15 +1531,19 @@ static void enable_swap_info(struct swap
> unsigned long *frontswap_map)
> {
> spin_lock(&swap_lock);
> + spin_lock(&p->lock);
> _enable_swap_info(p, prio, swap_map, frontswap_map);
> frontswap_init(p->type);
> + spin_unlock(&p->lock);
> spin_unlock(&swap_lock);
> }
>
> static void reinsert_swap_info(struct swap_info_struct *p)
> {
> spin_lock(&swap_lock);
> + spin_lock(&p->lock);
> _enable_swap_info(p, p->prio, p->swap_map, frontswap_map_get(p));
> + spin_unlock(&p->lock);
> spin_unlock(&swap_lock);
> }
>
> @@ -1547,14 +1603,16 @@ SYSCALL_DEFINE1(swapoff, const char __us
> /* just pick something that's safe... */
> swap_list.next = swap_list.head;
> }
> + spin_lock(&p->lock);
> if (p->prio < 0) {
> for (i = p->next; i >= 0; i = swap_info[i]->next)
> swap_info[i]->prio = p->prio--;
> least_priority++;
> }
> - nr_swap_pages -= p->pages;
> + atomic_long_sub(p->pages, &nr_swap_pages);
> total_swap_pages -= p->pages;
> p->flags &= ~SWP_WRITEOK;
> + spin_unlock(&p->lock);
> spin_unlock(&swap_lock);
>
> set_current_oom_origin();
> @@ -1573,14 +1631,17 @@ SYSCALL_DEFINE1(swapoff, const char __us
>
> mutex_lock(&swapon_mutex);
> spin_lock(&swap_lock);
> + spin_lock(&p->lock);
> drain_mmlist();
>
> /* wait for anyone still in scan_swap_map */
> p->highest_bit = 0; /* cuts scans short */
> while (p->flags >= SWP_SCANNING) {
> + spin_unlock(&p->lock);
> spin_unlock(&swap_lock);
> schedule_timeout_uninterruptible(1);
> spin_lock(&swap_lock);
> + spin_lock(&p->lock);
> }
>
> swap_file = p->swap_file;
> @@ -1590,6 +1651,7 @@ SYSCALL_DEFINE1(swapoff, const char __us
> p->swap_map = NULL;
> p->flags = 0;
> frontswap_invalidate_area(type);
> + spin_unlock(&p->lock);
> spin_unlock(&swap_lock);
> mutex_unlock(&swapon_mutex);
> vfree(swap_map);
> @@ -2117,7 +2179,7 @@ void si_swapinfo(struct sysinfo *val)
> if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK))
> nr_to_be_unused += si->inuse_pages;
> }
> - val->freeswap = nr_swap_pages + nr_to_be_unused;
> + val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused;
> val->totalswap = total_swap_pages + nr_to_be_unused;
> spin_unlock(&swap_lock);
> }
> @@ -2150,7 +2212,7 @@ static int __swap_duplicate(swp_entry_t
> p = swap_info[type];
> offset = swp_offset(entry);
>
> - spin_lock(&swap_lock);
> + spin_lock(&p->lock);
> if (unlikely(offset >= p->max))
> goto unlock_out;
>
> @@ -2185,7 +2247,7 @@ static int __swap_duplicate(swp_entry_t
> p->swap_map[offset] = count | has_cache;
>
> unlock_out:
> - spin_unlock(&swap_lock);
> + spin_unlock(&p->lock);
> out:
> return err;
>
> @@ -2310,7 +2372,7 @@ int add_swap_count_continuation(swp_entr
> }
>
> if (!page) {
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
> return -ENOMEM;
> }
>
> @@ -2358,7 +2420,7 @@ int add_swap_count_continuation(swp_entr
> list_add_tail(&page->lru, &head->lru);
> page = NULL; /* now it's attached, don't free it */
> out:
> - spin_unlock(&swap_lock);
> + spin_unlock(&si->lock);
> outer:
> if (page)
> __free_page(page);
> Index: linux/mm/vmscan.c
> ===================================================================
> --- linux.orig/mm/vmscan.c 2013-01-22 09:48:23.044725522 +0800
> +++ linux/mm/vmscan.c 2013-01-22 09:48:41.044499432 +0800
> @@ -1676,7 +1676,7 @@ static void get_scan_count(struct lruvec
> force_scan = true;
>
> /* If we have no swap space, do not bother scanning anon pages. */
> - if (!sc->may_swap || (nr_swap_pages <= 0)) {
> + if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
> noswap = 1;
> fraction[0] = 0;
> fraction[1] = 1;
> @@ -1831,7 +1831,7 @@ static inline bool should_continue_recla
> */
> pages_for_compaction = (2UL << sc->order);
> inactive_lru_pages = get_lru_size(lruvec, LRU_INACTIVE_FILE);
> - if (nr_swap_pages > 0)
> + if (get_nr_swap_pages() > 0)
> inactive_lru_pages += get_lru_size(lruvec, LRU_INACTIVE_ANON);
> if (sc->nr_reclaimed < pages_for_compaction &&
> inactive_lru_pages > pages_for_compaction)
> @@ -3053,7 +3053,7 @@ unsigned long global_reclaimable_pages(v
> nr = global_page_state(NR_ACTIVE_FILE) +
> global_page_state(NR_INACTIVE_FILE);
>
> - if (nr_swap_pages > 0)
> + if (get_nr_swap_pages() > 0)
> nr += global_page_state(NR_ACTIVE_ANON) +
> global_page_state(NR_INACTIVE_ANON);
>
> @@ -3067,7 +3067,7 @@ unsigned long zone_reclaimable_pages(str
> nr = zone_page_state(zone, NR_ACTIVE_FILE) +
> zone_page_state(zone, NR_INACTIVE_FILE);
>
> - if (nr_swap_pages > 0)
> + if (get_nr_swap_pages() > 0)
> nr += zone_page_state(zone, NR_ACTIVE_ANON) +
> zone_page_state(zone, NR_INACTIVE_ANON);
>
> Index: linux/mm/mmap.c
> ===================================================================
> --- linux.orig/mm/mmap.c 2013-01-22 09:48:23.052725417 +0800
> +++ linux/mm/mmap.c 2013-01-22 09:48:41.044499432 +0800
> @@ -143,7 +143,7 @@ int __vm_enough_memory(struct mm_struct
> */
> free -= global_page_state(NR_SHMEM);
>
> - free += nr_swap_pages;
> + free += get_nr_swap_pages();
>
> /*
> * Any slabs which are created with the
> Index: linux/mm/swap_state.c
> ===================================================================
> --- linux.orig/mm/swap_state.c 2013-01-22 09:48:23.036725746 +0800
> +++ linux/mm/swap_state.c 2013-01-22 09:48:41.044499432 +0800
> @@ -69,7 +69,8 @@ void show_swap_cache_info(void)
> printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
> swap_cache_info.add_total, swap_cache_info.del_total,
> swap_cache_info.find_success, swap_cache_info.find_total);
> - printk("Free swap = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10));
> + printk("Free swap = %ldkB\n",
> + get_nr_swap_pages() << (PAGE_SHIFT - 10));
> printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
> }
>
> Index: linux/drivers/staging/zcache/zcache-main.c
> ===================================================================
> --- linux.orig/drivers/staging/zcache/zcache-main.c 2013-01-22 09:48:23.084725036 +0800
> +++ linux/drivers/staging/zcache/zcache-main.c 2013-01-22 09:48:41.044499432 +0800
> @@ -927,8 +927,8 @@ static struct kobj_attribute zcache_zv_p
> */
>
> /* useful stats not collected by cleancache or frontswap */
> -static unsigned long zcache_flush_total;
> -static unsigned long zcache_flush_found;
> +static atomic_long_t zcache_flush_total;
> +static atomic_long_t zcache_flush_found;
> static unsigned long zcache_flobj_total;
> static unsigned long zcache_flobj_found;
> static unsigned long zcache_failed_eph_puts;
> @@ -1428,6 +1428,17 @@ static struct notifier_block zcache_cpu_
> .show = zcache_##_name##_show, \
> }
>
> +#define ZCACHE_SYSFS_RO_ATOMIC_LONG(_name) \
> + static ssize_t zcache_##_name##_show(struct kobject *kobj, \
> + struct kobj_attribute *attr, char *buf) \
> + { \
> + return sprintf(buf, "%lu\n", atomic_long_read(&zcache_##_name)); \
> + } \
> + static struct kobj_attribute zcache_##_name##_attr = { \
> + .attr = { .name = __stringify(_name), .mode = 0444 }, \
> + .show = zcache_##_name##_show, \
> + }
> +
> #define ZCACHE_SYSFS_RO_CUSTOM(_name, _func) \
> static ssize_t zcache_##_name##_show(struct kobject *kobj, \
> struct kobj_attribute *attr, char *buf) \
> @@ -1441,8 +1452,8 @@ static struct notifier_block zcache_cpu_
>
> ZCACHE_SYSFS_RO(curr_obj_count_max);
> ZCACHE_SYSFS_RO(curr_objnode_count_max);
> -ZCACHE_SYSFS_RO(flush_total);
> -ZCACHE_SYSFS_RO(flush_found);
> +ZCACHE_SYSFS_RO_ATOMIC_LONG(flush_total);
> +ZCACHE_SYSFS_RO_ATOMIC_LONG(flush_found);
> ZCACHE_SYSFS_RO(flobj_total);
> ZCACHE_SYSFS_RO(flobj_found);
> ZCACHE_SYSFS_RO(failed_eph_puts);
> @@ -1614,7 +1625,7 @@ static int zcache_flush_page(int cli_id,
> unsigned long flags;
>
> local_irq_save(flags);
> - zcache_flush_total++;
> + atomic_long_inc(&zcache_flush_total);
> pool = zcache_get_pool_by_id(cli_id, pool_id);
> if (likely(pool != NULL)) {
> if (atomic_read(&pool->obj_count) > 0)
> @@ -1622,7 +1633,7 @@ static int zcache_flush_page(int cli_id,
> zcache_put_pool(pool);
> }
> if (ret >= 0)
> - zcache_flush_found++;
> + atomic_long_inc(&zcache_flush_found);
> local_irq_restore(flags);
> return ret;
> }
>
> --
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