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Date: Wed, 22 Sep 2010 14:00:54 -0700
From: Dan Magenheimer <dan.magenheimer@...cle.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org, jeremy@...p.org,
hughd@...gle.com, ngupta@...are.org, JBeulich@...ell.com,
chris.mason@...cle.com, kurt.hackel@...cle.com,
dave.mccracken@...cle.com, npiggin@...nel.dk,
akpm@...ux-foundation.org, riel@...hat.com, mel@....ul.ie,
yinghan@...gle.com, gthelen@...gle.com, konrad.wilk@...cle.com
Subject: [PATCH V3 3/4] Frontswap: add hooks in swap subsystem and extend
[PATCH V3 3/4] Frontswap: add hooks in swap subsystem and extend
try_to_unuse so that frontswap_shrink can do a "partial swapoff"
Signed-off-by: Dan Magenheimer <dan.magenheimer@...cle.com>
Diffstat:
page_io.c | 12 ++++
swapfile.c | 58 +++++++++++++++++----
2 files changed, 61 insertions(+), 9 deletions(-)
--- linux-2.6.36-rc5/mm/swapfile.c 2010-09-20 17:56:53.000000000 -0600
+++ linux-2.6.36-rc5-frontswap/mm/swapfile.c 2010-09-22 09:45:01.000000000 -0600
@@ -30,6 +30,8 @@
#include <linux/capability.h>
#include <linux/syscalls.h>
#include <linux/memcontrol.h>
+#include <linux/frontswap.h>
+#include <linux/swapfile.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
@@ -41,7 +43,7 @@ static bool swap_count_continued(struct
static void free_swap_count_continuations(struct swap_info_struct *);
static sector_t map_swap_entry(swp_entry_t, struct block_device**);
-static DEFINE_SPINLOCK(swap_lock);
+DEFINE_SPINLOCK(swap_lock);
static unsigned int nr_swapfiles;
long nr_swap_pages;
long total_swap_pages;
@@ -52,9 +54,9 @@ static const char Unused_file[] = "Unuse
static const char Bad_offset[] = "Bad swap offset entry ";
static const char Unused_offset[] = "Unused swap offset entry ";
-static struct swap_list_t swap_list = {-1, -1};
+struct swap_list_t swap_list = {-1, -1};
-static struct swap_info_struct *swap_info[MAX_SWAPFILES];
+struct swap_info_struct *swap_info[MAX_SWAPFILES];
static DEFINE_MUTEX(swapon_mutex);
@@ -584,6 +586,7 @@ static unsigned char swap_entry_free(str
swap_list.next = p->type;
nr_swap_pages++;
p->inuse_pages--;
+ frontswap_flush_page(p->type, offset);
if ((p->flags & SWP_BLKDEV) &&
disk->fops->swap_slot_free_notify)
disk->fops->swap_slot_free_notify(p->bdev, offset);
@@ -1047,7 +1050,7 @@ static int unuse_mm(struct mm_struct *mm
* Recycle to start on reaching the end, returning 0 when empty.
*/
static unsigned int find_next_to_unuse(struct swap_info_struct *si,
- unsigned int prev)
+ unsigned int prev, bool frontswap)
{
unsigned int max = si->max;
unsigned int i = prev;
@@ -1073,6 +1076,12 @@ static unsigned int find_next_to_unuse(s
prev = 0;
i = 1;
}
+ if (frontswap) {
+ if (frontswap_test(si, i))
+ break;
+ else
+ continue;
+ }
count = si->swap_map[i];
if (count && swap_count(count) != SWAP_MAP_BAD)
break;
@@ -1084,8 +1093,12 @@ static unsigned int find_next_to_unuse(s
* We completely avoid races by reading each swap page in advance,
* and then search for the process using it. All the necessary
* page table adjustments can then be made atomically.
+ *
+ * if the boolean frontswap is true, only unuse pages_to_unuse pages;
+ * pages_to_unuse==0 means all pages
*/
-static int try_to_unuse(unsigned int type)
+int try_to_unuse(unsigned int type, bool frontswap,
+ unsigned long pages_to_unuse)
{
struct swap_info_struct *si = swap_info[type];
struct mm_struct *start_mm;
@@ -1118,7 +1131,7 @@ static int try_to_unuse(unsigned int typ
* one pass through swap_map is enough, but not necessarily:
* there are races when an instance of an entry might be missed.
*/
- while ((i = find_next_to_unuse(si, i)) != 0) {
+ while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
if (signal_pending(current)) {
retval = -EINTR;
break;
@@ -1285,6 +1298,10 @@ static int try_to_unuse(unsigned int typ
* interactive performance.
*/
cond_resched();
+ if (frontswap && pages_to_unuse > 0) {
+ if (!--pages_to_unuse)
+ break;
+ }
}
mmput(start_mm);
@@ -1610,7 +1627,7 @@ SYSCALL_DEFINE1(swapoff, const char __us
spin_unlock(&swap_lock);
current->flags |= PF_OOM_ORIGIN;
- err = try_to_unuse(type);
+ err = try_to_unuse(type, false, 0);
current->flags &= ~PF_OOM_ORIGIN;
if (err) {
@@ -1662,9 +1679,12 @@ SYSCALL_DEFINE1(swapoff, const char __us
swap_map = p->swap_map;
p->swap_map = NULL;
p->flags = 0;
+ frontswap_flush_area(type);
spin_unlock(&swap_lock);
mutex_unlock(&swapon_mutex);
vfree(swap_map);
+ if (p->frontswap_map)
+ vfree(p->frontswap_map);
/* Destroy swap account informatin */
swap_cgroup_swapoff(type);
@@ -1820,6 +1840,7 @@ SYSCALL_DEFINE2(swapon, const char __use
unsigned long maxpages;
unsigned long swapfilepages;
unsigned char *swap_map = NULL;
+ unsigned long *frontswap_map = NULL;
struct page *page = NULL;
struct inode *inode = NULL;
int did_down = 0;
@@ -2041,6 +2062,12 @@ SYSCALL_DEFINE2(swapon, const char __use
error = -EINVAL;
goto bad_swap;
}
+ /* frontswap enabled? set up bit-per-page map for frontswap */
+ if (frontswap_enabled) {
+ frontswap_map = vmalloc(maxpages / sizeof(long));
+ if (frontswap_map)
+ memset(frontswap_map, 0, maxpages / sizeof(long));
+ }
if (p->bdev) {
if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
@@ -2059,16 +2086,18 @@ SYSCALL_DEFINE2(swapon, const char __use
else
p->prio = --least_priority;
p->swap_map = swap_map;
+ p->frontswap_map = frontswap_map;
p->flags |= SWP_WRITEOK;
nr_swap_pages += nr_good_pages;
total_swap_pages += nr_good_pages;
printk(KERN_INFO "Adding %uk swap on %s. "
- "Priority:%d extents:%d across:%lluk %s%s\n",
+ "Priority:%d extents:%d across:%lluk %s%s%s\n",
nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
- (p->flags & SWP_DISCARDABLE) ? "D" : "");
+ (p->flags & SWP_DISCARDABLE) ? "D" : "",
+ (p->frontswap_map) ? "FS" : "");
/* insert swap space into swap_list: */
prev = -1;
@@ -2082,6 +2111,7 @@ SYSCALL_DEFINE2(swapon, const char __use
swap_list.head = swap_list.next = type;
else
swap_info[prev]->next = type;
+ frontswap_init(type);
spin_unlock(&swap_lock);
mutex_unlock(&swapon_mutex);
error = 0;
@@ -2266,6 +2296,10 @@ int valid_swaphandles(swp_entry_t entry,
base++;
spin_lock(&swap_lock);
+ if (frontswap_test(si, target)) {
+ spin_unlock(&swap_lock);
+ return 0;
+ }
if (end > si->max) /* don't go beyond end of map */
end = si->max;
@@ -2276,6 +2310,9 @@ int valid_swaphandles(swp_entry_t entry,
break;
if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
break;
+ /* Don't read in frontswap pages */
+ if (frontswap_test(si, toff))
+ break;
}
/* Count contiguous allocated slots below our target */
for (toff = target; --toff >= base; nr_pages++) {
@@ -2284,6 +2321,9 @@ int valid_swaphandles(swp_entry_t entry,
break;
if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
break;
+ /* Don't read in frontswap pages */
+ if (frontswap_test(si, toff))
+ break;
}
spin_unlock(&swap_lock);
--- linux-2.6.36-rc5/mm/page_io.c 2010-09-20 17:56:53.000000000 -0600
+++ linux-2.6.36-rc5-frontswap/mm/page_io.c 2010-09-21 13:58:02.000000000 -0600
@@ -18,6 +18,7 @@
#include <linux/bio.h>
#include <linux/swapops.h>
#include <linux/writeback.h>
+#include <linux/frontswap.h>
#include <asm/pgtable.h>
static struct bio *get_swap_bio(gfp_t gfp_flags,
@@ -98,6 +99,12 @@ int swap_writepage(struct page *page, st
unlock_page(page);
goto out;
}
+ if (frontswap_put_page(page) == 0) {
+ set_page_writeback(page);
+ unlock_page(page);
+ end_page_writeback(page);
+ goto out;
+ }
bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
if (bio == NULL) {
set_page_dirty(page);
@@ -122,6 +129,11 @@ int swap_readpage(struct page *page)
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(PageUptodate(page));
+ if (frontswap_get_page(page) == 0) {
+ SetPageUptodate(page);
+ unlock_page(page);
+ goto out;
+ }
bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
if (bio == NULL) {
unlock_page(page);
--
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