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authorHugh Dickins <hugh@veritas.com>2009-01-06 14:39:50 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 15:59:05 -0800
commitebebbbe904634b0ca1c674457b399f68db5e05b1 (patch)
tree168c6c1193580e40ba1916ebaff822e15e8ee186 /mm/swapfile.c
parent81e33971271ec8603fe696731ff9967afb99e729 (diff)
swapfile: rearrange scan and swap_info
Before making functional changes, rearrange scan_swap_map() to simplify subsequent diffs. Actually, there is one functional change in there: leave cluster_nr negative while scanning for a new cluster - resetting it early increased the likelihood that when we have difficulty finding a free cluster, another task may come in and try doing exactly the same - just a waste of cpu. Before making functional changes, rearrange struct swap_info_struct slightly: flags will be needed as an unsigned long (for wait_on_bit), next is a good int to pair with prio, old_block_size is uninteresting so shift it to the end. Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c66
1 files changed, 37 insertions, 29 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 85ff603385c..4d9855f86e7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -89,7 +89,8 @@ void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
static inline unsigned long scan_swap_map(struct swap_info_struct *si)
{
- unsigned long offset, last_in_cluster;
+ unsigned long offset;
+ unsigned long last_in_cluster;
int latency_ration = LATENCY_LIMIT;
/*
@@ -103,10 +104,13 @@ static inline unsigned long scan_swap_map(struct swap_info_struct *si)
*/
si->flags += SWP_SCANNING;
- if (unlikely(!si->cluster_nr)) {
- si->cluster_nr = SWAPFILE_CLUSTER - 1;
- if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
- goto lowest;
+ offset = si->cluster_next;
+
+ if (unlikely(!si->cluster_nr--)) {
+ if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
+ si->cluster_nr = SWAPFILE_CLUSTER - 1;
+ goto checks;
+ }
spin_unlock(&swap_lock);
offset = si->lowest_bit;
@@ -118,43 +122,47 @@ static inline unsigned long scan_swap_map(struct swap_info_struct *si)
last_in_cluster = offset + SWAPFILE_CLUSTER;
else if (offset == last_in_cluster) {
spin_lock(&swap_lock);
- si->cluster_next = offset-SWAPFILE_CLUSTER+1;
- goto cluster;
+ offset -= SWAPFILE_CLUSTER - 1;
+ si->cluster_next = offset;
+ si->cluster_nr = SWAPFILE_CLUSTER - 1;
+ goto checks;
}
if (unlikely(--latency_ration < 0)) {
cond_resched();
latency_ration = LATENCY_LIMIT;
}
}
+
+ offset = si->lowest_bit;
spin_lock(&swap_lock);
- goto lowest;
+ si->cluster_nr = SWAPFILE_CLUSTER - 1;
}
- si->cluster_nr--;
-cluster:
- offset = si->cluster_next;
- if (offset > si->highest_bit)
-lowest: offset = si->lowest_bit;
-checks: if (!(si->flags & SWP_WRITEOK))
+checks:
+ if (!(si->flags & SWP_WRITEOK))
goto no_page;
if (!si->highest_bit)
goto no_page;
- if (!si->swap_map[offset]) {
- if (offset == si->lowest_bit)
- si->lowest_bit++;
- if (offset == si->highest_bit)
- si->highest_bit--;
- si->inuse_pages++;
- if (si->inuse_pages == si->pages) {
- si->lowest_bit = si->max;
- si->highest_bit = 0;
- }
- si->swap_map[offset] = 1;
- si->cluster_next = offset + 1;
- si->flags -= SWP_SCANNING;
- return offset;
+ if (offset > si->highest_bit)
+ offset = si->lowest_bit;
+ if (si->swap_map[offset])
+ goto scan;
+
+ if (offset == si->lowest_bit)
+ si->lowest_bit++;
+ if (offset == si->highest_bit)
+ si->highest_bit--;
+ si->inuse_pages++;
+ if (si->inuse_pages == si->pages) {
+ si->lowest_bit = si->max;
+ si->highest_bit = 0;
}
+ si->swap_map[offset] = 1;
+ si->cluster_next = offset + 1;
+ si->flags -= SWP_SCANNING;
+ return offset;
+scan:
spin_unlock(&swap_lock);
while (++offset <= si->highest_bit) {
if (!si->swap_map[offset]) {
@@ -167,7 +175,7 @@ checks: if (!(si->flags & SWP_WRITEOK))
}
}
spin_lock(&swap_lock);
- goto lowest;
+ goto checks;
no_page:
si->flags -= SWP_SCANNING;