Messages in this thread Patch in this message | | | Date | Sat, 9 Jul 2005 01:07:37 +0100 (BST) | From | Hugh Dickins <> | Subject | [PATCH 08/13] get_swap_page drop swap_list_lock |
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Rewrite get_swap_page to allocate in just the same sequence as before, but without holding swap_list_lock across its scan_swap_map. Decrement nr_swap_pages and update swap_list.next in advance, while still holding swap_list_lock. Skip full devices by testing highest_bit. Swapoff hold swap_device_lock as well as swap_list_lock to clear SWP_WRITEOK. Reduces lock contention when there are parallel swap devices of the same priority.
Signed-off-by: Hugh Dickins <hugh@veritas.com> ---
mm/swapfile.c | 73 +++++++++++++++++++++++++++------------------------------- 1 files changed, 35 insertions(+), 38 deletions(-)
--- swap7/mm/swapfile.c 2005-07-08 19:14:39.000000000 +0100 +++ swap8/mm/swapfile.c 2005-07-08 19:14:54.000000000 +0100 @@ -137,7 +137,6 @@ static inline unsigned long scan_swap_ma } si->swap_map[offset] = 1; si->inuse_pages++; - nr_swap_pages--; si->cluster_next = offset+1; return offset; } @@ -148,50 +147,45 @@ static inline unsigned long scan_swap_ma swp_entry_t get_swap_page(void) { - struct swap_info_struct * p; - unsigned long offset; - swp_entry_t entry; - int type, wrapped = 0; + struct swap_info_struct *si; + pgoff_t offset; + int type, next; + int wrapped = 0; - entry.val = 0; /* Out of memory */ swap_list_lock(); - type = swap_list.next; - if (type < 0) - goto out; if (nr_swap_pages <= 0) - goto out; + goto noswap; + nr_swap_pages--; - while (1) { - p = &swap_info[type]; - if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) { - swap_device_lock(p); - offset = scan_swap_map(p); - swap_device_unlock(p); - if (offset) { - entry = swp_entry(type,offset); - type = swap_info[type].next; - if (type < 0 || - p->prio != swap_info[type].prio) { - swap_list.next = swap_list.head; - } else { - swap_list.next = type; - } - goto out; - } + for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { + si = swap_info + type; + next = si->next; + if (next < 0 || + (!wrapped && si->prio != swap_info[next].prio)) { + next = swap_list.head; + wrapped++; } - type = p->next; - if (!wrapped) { - if (type < 0 || p->prio != swap_info[type].prio) { - type = swap_list.head; - wrapped = 1; - } - } else - if (type < 0) - goto out; /* out of swap space */ + + if (!si->highest_bit) + continue; + if (!(si->flags & SWP_WRITEOK)) + continue; + + swap_list.next = next; + swap_device_lock(si); + swap_list_unlock(); + offset = scan_swap_map(si); + swap_device_unlock(si); + if (offset) + return swp_entry(type, offset); + swap_list_lock(); + next = swap_list.next; } -out: + + nr_swap_pages++; +noswap: swap_list_unlock(); - return entry; + return (swp_entry_t) {0}; } static struct swap_info_struct * swap_info_get(swp_entry_t entry) @@ -1103,8 +1097,11 @@ asmlinkage long sys_swapoff(const char _ } nr_swap_pages -= p->pages; total_swap_pages -= p->pages; + swap_device_lock(p); p->flags &= ~SWP_WRITEOK; + swap_device_unlock(p); swap_list_unlock(); + current->flags |= PF_SWAPOFF; err = try_to_unuse(type); current->flags &= ~PF_SWAPOFF; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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