The patch titled
swap: get_swap_page drop swap_list_lock
has been added to the -mm tree. Its filename is
swap-get_swap_page-drop-swap_list_lock.patch
Patches currently in -mm which might be from [EMAIL PROTECTED] are
swap-update-swapfile-i_sem-comment.patch
swap-correct-swapfile-nr_good_pages.patch
swap-move-destroy_swap_extents-calls.patch
swap-swap-extent-list-is-ordered.patch
swap-show-span-of-swap-extents.patch
swap-swap-unsigned-int-consistency.patch
swap-freeing-update-swap_listnext.patch
swap-get_swap_page-drop-swap_list_lock.patch
swap-scan_swap_map-restyled.patch
swap-scan_swap_map-drop-swap_device_lock.patch
swap-scan_swap_map-latency-breaks.patch
swap-swap_lock-replace-listdevice.patch
swap-update-swsusp-use-of-swap_info.patch
From: Hugh Dickins <[EMAIL PROTECTED]>
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 <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
mm/swapfile.c | 73 +++++++++++++++++++++++++++-------------------------------
1 files changed, 35 insertions(+), 38 deletions(-)
diff -puN mm/swapfile.c~swap-get_swap_page-drop-swap_list_lock mm/swapfile.c
--- devel/mm/swapfile.c~swap-get_swap_page-drop-swap_list_lock 2005-07-08
22:34:52.000000000 -0700
+++ devel-akpm/mm/swapfile.c 2005-07-08 22:34:52.000000000 -0700
@@ -139,7 +139,6 @@ 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;
}
@@ -150,50 +149,45 @@ 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)
@@ -1105,8 +1099,11 @@ 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;
_
-
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