DESC
/proc/swaps negative Used
EDESC
From: Hugh Dickins <hugh@veritas.com>
Your swapspace-layout-improvements.patch inadvertently deletes a line too
many, so /proc/swaps tends to show negative Used.
I was tempted to delete "akpm", but compassion stayed my hand.
Sorry, I'm sure you'd appreciate proper feedback on the patch, but I
haven't studied it or noticed its impact yet.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/linux/swap.h | 6 +-
25-akpm/kernel/power/swsusp.c | 2
25-akpm/mm/shmem.c | 4 -
25-akpm/mm/swap_state.c | 8 ++-
25-akpm/mm/swapfile.c | 98 +++++++++++++++++-------------------------
25-akpm/mm/vmscan.c | 5 +-
6 files changed, 56 insertions(+), 67 deletions(-)
diff -puN include/linux/swap.h~swapspace-layout-improvements include/linux/swap.h
--- 25/include/linux/swap.h~swapspace-layout-improvements 2005-02-23 02:02:46.000000000 -0800
+++ 25-akpm/include/linux/swap.h 2005-02-23 02:02:46.000000000 -0800
@@ -193,7 +193,7 @@ extern int rw_swap_page_sync(int, swp_en
extern struct address_space swapper_space;
#define total_swapcache_pages swapper_space.nrpages
extern void show_swap_cache_info(void);
-extern int add_to_swap(struct page *);
+extern int add_to_swap(struct page *page, void *cookie, pgoff_t index);
extern void __delete_from_swap_cache(struct page *);
extern void delete_from_swap_cache(struct page *);
extern int move_to_swap_cache(struct page *, swp_entry_t);
@@ -209,7 +209,7 @@ extern long total_swap_pages;
extern unsigned int nr_swapfiles;
extern struct swap_info_struct swap_info[];
extern void si_swapinfo(struct sysinfo *);
-extern swp_entry_t get_swap_page(void);
+extern swp_entry_t get_swap_page(void *cookie, pgoff_t index);
extern int swap_duplicate(swp_entry_t);
extern int valid_swaphandles(swp_entry_t, unsigned long *);
extern void swap_free(swp_entry_t);
@@ -276,7 +276,7 @@ static inline int remove_exclusive_swap_
return 0;
}
-static inline swp_entry_t get_swap_page(void)
+static inline swp_entry_t get_swap_page(void *cookie, pgoff_t index)
{
swp_entry_t entry;
entry.val = 0;
diff -puN kernel/power/swsusp.c~swapspace-layout-improvements kernel/power/swsusp.c
--- 25/kernel/power/swsusp.c~swapspace-layout-improvements 2005-02-23 02:02:46.000000000 -0800
+++ 25-akpm/kernel/power/swsusp.c 2005-02-23 02:02:46.000000000 -0800
@@ -245,7 +245,7 @@ static int write_page(unsigned long addr
swp_entry_t entry;
int error = 0;
- entry = get_swap_page();
+ entry = get_swap_page(NULL, swp_offset(*loc));
if (swp_offset(entry) &&
swapfile_used[swp_type(entry)] == SWAPFILE_SUSPEND) {
error = rw_swap_page_sync(WRITE, entry,
diff -puN mm/shmem.c~swapspace-layout-improvements mm/shmem.c
--- 25/mm/shmem.c~swapspace-layout-improvements 2005-02-23 02:02:46.000000000 -0800
+++ 25-akpm/mm/shmem.c 2005-02-23 02:02:46.000000000 -0800
@@ -812,7 +812,7 @@ static int shmem_writepage(struct page *
struct shmem_inode_info *info;
swp_entry_t *entry, swap;
struct address_space *mapping;
- unsigned long index;
+ pgoff_t index;
struct inode *inode;
BUG_ON(!PageLocked(page));
@@ -824,7 +824,7 @@ static int shmem_writepage(struct page *
info = SHMEM_I(inode);
if (info->flags & VM_LOCKED)
goto redirty;
- swap = get_swap_page();
+ swap = get_swap_page(mapping, index);
if (!swap.val)
goto redirty;
diff -puN mm/swapfile.c~swapspace-layout-improvements mm/swapfile.c
--- 25/mm/swapfile.c~swapspace-layout-improvements 2005-02-23 02:02:46.000000000 -0800
+++ 25-akpm/mm/swapfile.c 2005-02-23 02:04:53.000000000 -0800
@@ -13,6 +13,7 @@
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/vmalloc.h>
+#include <linux/hash.h>
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/shm.h>
@@ -85,71 +86,52 @@ void swap_unplug_io_fn(struct backing_de
up_read(&swap_unplug_sem);
}
-static inline int scan_swap_map(struct swap_info_struct *si)
-{
- unsigned long offset;
- /*
- * We try to cluster swap pages by allocating them
- * sequentially in swap. Once we've allocated
- * SWAPFILE_CLUSTER pages this way, however, we resort to
- * first-free allocation, starting a new cluster. This
- * prevents us from scattering swap pages all over the entire
- * swap partition, so that we reduce overall disk seek times
- * between swap pages. -- sct */
- if (si->cluster_nr) {
- while (si->cluster_next <= si->highest_bit) {
- offset = si->cluster_next++;
- if (si->swap_map[offset])
- continue;
- si->cluster_nr--;
- goto got_page;
- }
- }
- si->cluster_nr = SWAPFILE_CLUSTER;
+int akpm;
- /* try to find an empty (even not aligned) cluster. */
- offset = si->lowest_bit;
- check_next_cluster:
- if (offset+SWAPFILE_CLUSTER-1 <= si->highest_bit)
- {
- unsigned long nr;
- for (nr = offset; nr < offset+SWAPFILE_CLUSTER; nr++)
- if (si->swap_map[nr])
- {
- offset = nr+1;
- goto check_next_cluster;
- }
- /* We found a completly empty cluster, so start
- * using it.
- */
- goto got_page;
- }
- /* No luck, so now go finegrined as usual. -Andrea */
- for (offset = si->lowest_bit; offset <= si->highest_bit ; offset++) {
- if (si->swap_map[offset])
+/*
+ * We divide the swapdev into 1024 kilobyte chunks. We use the cookie and the
+ * upper bits of the index to select a chunk and the rest of the index as the
+ * offset into the selected chunk.
+ */
+#define CHUNK_SHIFT (20 - PAGE_SHIFT)
+#define CHUNK_MASK (-1UL << CHUNK_SHIFT)
+
+static int
+scan_swap_map(struct swap_info_struct *si, void *cookie, pgoff_t index)
+{
+ unsigned long chunk;
+ unsigned long nchunks;
+ unsigned long block;
+ unsigned long scan;
+
+ nchunks = si->max >> CHUNK_SHIFT;
+ chunk = 0;
+ if (nchunks)
+ chunk = hash_long((unsigned long)cookie + (index & CHUNK_MASK),
+ BITS_PER_LONG) % nchunks;
+
+ block = (chunk << CHUNK_SHIFT) + (index & ~CHUNK_MASK);
+
+ for (scan = 0; scan < si->max; scan++, block++) {
+ if (block == si->max)
+ block = 0;
+ if (block == 0)
continue;
- si->lowest_bit = offset+1;
- got_page:
- if (offset == si->lowest_bit)
- si->lowest_bit++;
- if (offset == si->highest_bit)
- si->highest_bit--;
- if (si->lowest_bit > si->highest_bit) {
- si->lowest_bit = si->max;
- si->highest_bit = 0;
- }
- si->swap_map[offset] = 1;
+ if (si->swap_map[block])
+ continue;
+ si->swap_map[block] = 1;
si->inuse_pages++;
nr_swap_pages--;
- si->cluster_next = offset+1;
- return offset;
+ if (akpm)
+ printk("cookie:%p, index:%lu, chunk:%lu nchunks:%lu "
+ "block:%lu\n",
+ cookie, index, chunk, nchunks, block);
+ return block;
}
- si->lowest_bit = si->max;
- si->highest_bit = 0;
return 0;
}
-swp_entry_t get_swap_page(void)
+swp_entry_t get_swap_page(void *cookie, pgoff_t index)
{
struct swap_info_struct * p;
unsigned long offset;
@@ -168,7 +150,7 @@ swp_entry_t get_swap_page(void)
p = &swap_info[type];
if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
swap_device_lock(p);
- offset = scan_swap_map(p);
+ offset = scan_swap_map(p, cookie, index);
swap_device_unlock(p);
if (offset) {
entry = swp_entry(type,offset);
diff -puN mm/swap_state.c~swapspace-layout-improvements mm/swap_state.c
--- 25/mm/swap_state.c~swapspace-layout-improvements 2005-02-23 02:02:46.000000000 -0800
+++ 25-akpm/mm/swap_state.c 2005-02-23 02:02:46.000000000 -0800
@@ -139,8 +139,12 @@ void __delete_from_swap_cache(struct pag
*
* Allocate swap space for the page and add the page to the
* swap cache. Caller needs to hold the page lock.
+ *
+ * We attempt to lay pages out on swap to that virtually-contiguous pages are
+ * contiguous on-disk. To do this we utilise page->index (offset into vma) and
+ * page->mapping (the anon_vma's address).
*/
-int add_to_swap(struct page * page)
+int add_to_swap(struct page *page, void *cookie, pgoff_t index)
{
swp_entry_t entry;
int pf_flags;
@@ -150,7 +154,7 @@ int add_to_swap(struct page * page)
BUG();
for (;;) {
- entry = get_swap_page();
+ entry = get_swap_page(cookie, index);
if (!entry.val)
return 0;
diff -puN mm/vmscan.c~swapspace-layout-improvements mm/vmscan.c
--- 25/mm/vmscan.c~swapspace-layout-improvements 2005-02-23 02:02:46.000000000 -0800
+++ 25-akpm/mm/vmscan.c 2005-02-23 02:04:48.000000000 -0800
@@ -397,7 +397,10 @@ static int shrink_list(struct list_head
* Try to allocate it some swap space here.
*/
if (PageAnon(page) && !PageSwapCache(page)) {
- if (!add_to_swap(page))
+ void *cookie = page->mapping;
+ pgoff_t index = page->index;
+
+ if (!add_to_swap(page, cookie, index))
goto activate_locked;
}
#endif /* CONFIG_SWAP */
_