* [PATCH 1/3] z3fold: make counters atomic
2016-10-13 16:47 [PATCHv4 0/3] z3fold: add shrinker Vitaly Wool
@ 2016-10-13 16:49 ` Vitaly Wool
2016-10-13 16:50 ` [PATCH 2/3] z3fold: remove redundant locking Vitaly Wool
2016-10-13 16:52 ` [PATCH 3/3] z3fold: add shrinker Vitaly Wool
2 siblings, 0 replies; 4+ messages in thread
From: Vitaly Wool @ 2016-10-13 16:49 UTC (permalink / raw)
To: Linux-MM, linux-kernel; +Cc: Dan Streetman, Andrew Morton, Dave Chinner
This patch converts pages_nr per-pool counter to atomic64_t.
It also introduces a new counter, unbuddied_nr, which is also
atomic64_t, to track the number of unbuddied (shrinkable) pages,
as a step to prepare for z3fold shrinker implementation.
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
---
mm/z3fold.c | 33 +++++++++++++++++++++++++--------
1 file changed, 25 insertions(+), 8 deletions(-)
diff --git a/mm/z3fold.c b/mm/z3fold.c
index 8f9e89c..5197d7b 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -69,6 +69,7 @@ struct z3fold_ops {
* @lru: list tracking the z3fold pages in LRU order by most recently
* added buddy.
* @pages_nr: number of z3fold pages in the pool.
+ * @unbuddied_nr: number of unbuddied z3fold pages in the pool.
* @ops: pointer to a structure of user defined operations specified at
* pool creation time.
*
@@ -80,7 +81,8 @@ struct z3fold_pool {
struct list_head unbuddied[NCHUNKS];
struct list_head buddied;
struct list_head lru;
- u64 pages_nr;
+ atomic64_t pages_nr;
+ atomic64_t unbuddied_nr;
const struct z3fold_ops *ops;
struct zpool *zpool;
const struct zpool_ops *zpool_ops;
@@ -234,7 +236,8 @@ static struct z3fold_pool *z3fold_create_pool(gfp_t gfp,
INIT_LIST_HEAD(&pool->unbuddied[i]);
INIT_LIST_HEAD(&pool->buddied);
INIT_LIST_HEAD(&pool->lru);
- pool->pages_nr = 0;
+ atomic64_set(&pool->pages_nr, 0);
+ atomic64_set(&pool->unbuddied_nr, 0);
pool->ops = ops;
return pool;
}
@@ -334,6 +337,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
continue;
}
list_del(&zhdr->buddy);
+ atomic64_dec(&pool->unbuddied_nr);
goto found;
}
}
@@ -346,7 +350,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
if (!page)
return -ENOMEM;
spin_lock(&pool->lock);
- pool->pages_nr++;
+ atomic64_inc(&pool->pages_nr);
zhdr = init_z3fold_page(page);
if (bud == HEADLESS) {
@@ -369,6 +373,7 @@ found:
/* Add to unbuddied list */
freechunks = num_free_chunks(zhdr);
list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
+ atomic64_inc(&pool->unbuddied_nr);
} else {
/* Add to buddied list */
list_add(&zhdr->buddy, &pool->buddied);
@@ -412,6 +417,11 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
/* HEADLESS page stored */
bud = HEADLESS;
} else {
+ if (zhdr->first_chunks == 0 ||
+ zhdr->middle_chunks == 0 ||
+ zhdr->last_chunks == 0)
+ atomic64_dec(&pool->unbuddied_nr);
+
bud = handle_to_buddy(handle);
switch (bud) {
@@ -429,6 +439,7 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
pr_err("%s: unknown bud %d\n", __func__, bud);
WARN_ON(1);
spin_unlock(&pool->lock);
+ atomic64_inc(&pool->unbuddied_nr);
return;
}
}
@@ -451,12 +462,13 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
list_del(&page->lru);
clear_bit(PAGE_HEADLESS, &page->private);
free_z3fold_page(zhdr);
- pool->pages_nr--;
+ atomic64_dec(&pool->pages_nr);
} else {
z3fold_compact_page(zhdr);
/* Add to the unbuddied list */
freechunks = num_free_chunks(zhdr);
list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
+ atomic64_inc(&pool->unbuddied_nr);
}
spin_unlock(&pool->lock);
@@ -520,6 +532,11 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
zhdr = page_address(page);
if (!test_bit(PAGE_HEADLESS, &page->private)) {
list_del(&zhdr->buddy);
+ if (zhdr->first_chunks == 0 ||
+ zhdr->middle_chunks == 0 ||
+ zhdr->last_chunks == 0)
+ atomic64_dec(&pool->unbuddied_nr);
+
/*
* We need encode the handles before unlocking, since
* we can race with free that will set
@@ -569,7 +586,7 @@ next:
*/
clear_bit(PAGE_HEADLESS, &page->private);
free_z3fold_page(zhdr);
- pool->pages_nr--;
+ atomic64_dec(&pool->pages_nr);
spin_unlock(&pool->lock);
return 0;
} else if (!test_bit(PAGE_HEADLESS, &page->private)) {
@@ -584,6 +601,7 @@ next:
freechunks = num_free_chunks(zhdr);
list_add(&zhdr->buddy,
&pool->unbuddied[freechunks]);
+ atomic64_inc(&pool->unbuddied_nr);
}
}
@@ -672,12 +690,11 @@ static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
* z3fold_get_pool_size() - gets the z3fold pool size in pages
* @pool: pool whose size is being queried
*
- * Returns: size in pages of the given pool. The pool lock need not be
- * taken to access pages_nr.
+ * Returns: size in pages of the given pool.
*/
static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
{
- return pool->pages_nr;
+ return atomic64_read(&pool->pages_nr);
}
/*****************
--
2.4.2
^ permalink raw reply [flat|nested] 4+ messages in thread* [PATCH 2/3] z3fold: remove redundant locking
2016-10-13 16:47 [PATCHv4 0/3] z3fold: add shrinker Vitaly Wool
2016-10-13 16:49 ` [PATCH 1/3] z3fold: make counters atomic Vitaly Wool
@ 2016-10-13 16:50 ` Vitaly Wool
2016-10-13 16:52 ` [PATCH 3/3] z3fold: add shrinker Vitaly Wool
2 siblings, 0 replies; 4+ messages in thread
From: Vitaly Wool @ 2016-10-13 16:50 UTC (permalink / raw)
To: Linux-MM, linux-kernel; +Cc: Dan Streetman, Andrew Morton, Dave Chinner
The per-pool z3fold spinlock should generally be taken only when
a non-atomic pool variable is modified. There's no need to take it
to map/unmap an object.
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
---
mm/z3fold.c | 17 +++++------------
1 file changed, 5 insertions(+), 12 deletions(-)
diff --git a/mm/z3fold.c b/mm/z3fold.c
index 5197d7b..10513b5 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -580,6 +580,7 @@ next:
if ((test_bit(PAGE_HEADLESS, &page->private) && ret == 0) ||
(zhdr->first_chunks == 0 && zhdr->last_chunks == 0 &&
zhdr->middle_chunks == 0)) {
+ spin_unlock(&pool->lock);
/*
* All buddies are now free, free the z3fold page and
* return success.
@@ -587,7 +588,6 @@ next:
clear_bit(PAGE_HEADLESS, &page->private);
free_z3fold_page(zhdr);
atomic64_dec(&pool->pages_nr);
- spin_unlock(&pool->lock);
return 0;
} else if (!test_bit(PAGE_HEADLESS, &page->private)) {
if (zhdr->first_chunks != 0 &&
@@ -629,7 +629,6 @@ static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
void *addr;
enum buddy buddy;
- spin_lock(&pool->lock);
zhdr = handle_to_z3fold_header(handle);
addr = zhdr;
page = virt_to_page(zhdr);
@@ -656,7 +655,6 @@ static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
break;
}
out:
- spin_unlock(&pool->lock);
return addr;
}
@@ -671,19 +669,14 @@ static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
struct page *page;
enum buddy buddy;
- spin_lock(&pool->lock);
zhdr = handle_to_z3fold_header(handle);
page = virt_to_page(zhdr);
- if (test_bit(PAGE_HEADLESS, &page->private)) {
- spin_unlock(&pool->lock);
- return;
+ if (!test_bit(PAGE_HEADLESS, &page->private)) {
+ buddy = handle_to_buddy(handle);
+ if (buddy == MIDDLE)
+ clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
}
-
- buddy = handle_to_buddy(handle);
- if (buddy == MIDDLE)
- clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
- spin_unlock(&pool->lock);
}
/**
--
2.4.2
^ permalink raw reply [flat|nested] 4+ messages in thread* [PATCH 3/3] z3fold: add shrinker
2016-10-13 16:47 [PATCHv4 0/3] z3fold: add shrinker Vitaly Wool
2016-10-13 16:49 ` [PATCH 1/3] z3fold: make counters atomic Vitaly Wool
2016-10-13 16:50 ` [PATCH 2/3] z3fold: remove redundant locking Vitaly Wool
@ 2016-10-13 16:52 ` Vitaly Wool
2 siblings, 0 replies; 4+ messages in thread
From: Vitaly Wool @ 2016-10-13 16:52 UTC (permalink / raw)
To: Linux-MM, linux-kernel; +Cc: Dan Streetman, Andrew Morton, Dave Chinner
This patch implements shrinker for z3fold. This shrinker
implementation does not free up any pages directly but it allows
for a denser placement of compressed objects which results in
less actual pages consumed and higher compression ratio therefore.
This patch has been checked with the latest Linus's tree.
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
---
mm/z3fold.c | 136 +++++++++++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 111 insertions(+), 25 deletions(-)
diff --git a/mm/z3fold.c b/mm/z3fold.c
index 10513b5..0b2a0d3 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -27,6 +27,7 @@
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/preempt.h>
+#include <linux/shrinker.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/zpool.h>
@@ -72,6 +73,7 @@ struct z3fold_ops {
* @unbuddied_nr: number of unbuddied z3fold pages in the pool.
* @ops: pointer to a structure of user defined operations specified at
* pool creation time.
+ * @shrinker: shrinker structure to optimize page layout in background
*
* This structure is allocated at pool creation time and maintains metadata
* pertaining to a particular z3fold pool.
@@ -86,6 +88,7 @@ struct z3fold_pool {
const struct z3fold_ops *ops;
struct zpool *zpool;
const struct zpool_ops *zpool_ops;
+ struct shrinker shrinker;
};
enum buddy {
@@ -136,6 +139,9 @@ static int size_to_chunks(size_t size)
#define for_each_unbuddied_list(_iter, _begin) \
for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
+#define for_each_unbuddied_list_down(_iter, _end) \
+ for ((_iter) = (_end); (_iter) > 0; (_iter)--)
+
/* Initializes the z3fold header of a newly allocated z3fold page */
static struct z3fold_header *init_z3fold_page(struct page *page)
{
@@ -211,6 +217,96 @@ static int num_free_chunks(struct z3fold_header *zhdr)
return nfree;
}
+/* Has to be called with lock held */
+static int z3fold_compact_page(struct z3fold_header *zhdr, bool sync)
+{
+ struct page *page = virt_to_page(zhdr);
+ void *beg = zhdr;
+
+
+ if (!test_bit(MIDDLE_CHUNK_MAPPED, &page->private)) {
+ if (zhdr->middle_chunks != 0 &&
+ zhdr->first_chunks == 0 &&
+ zhdr->last_chunks == 0) {
+ memmove(beg + ZHDR_SIZE_ALIGNED,
+ beg + (zhdr->start_middle << CHUNK_SHIFT),
+ zhdr->middle_chunks << CHUNK_SHIFT);
+ zhdr->first_chunks = zhdr->middle_chunks;
+ zhdr->middle_chunks = 0;
+ zhdr->start_middle = 0;
+ zhdr->first_num++;
+ return 1;
+ }
+ if (sync)
+ goto out;
+
+ /* moving data is expensive, so let's only do that if
+ * there's substantial gain (2+ chunks)
+ */
+ if (zhdr->middle_chunks != 0 && zhdr->first_chunks != 0 &&
+ zhdr->last_chunks == 0 &&
+ zhdr->start_middle > zhdr->first_chunks + 2) {
+ unsigned short new_start = zhdr->first_chunks + 1;
+ memmove(beg + (new_start << CHUNK_SHIFT),
+ beg + (zhdr->start_middle << CHUNK_SHIFT),
+ zhdr->middle_chunks << CHUNK_SHIFT);
+ zhdr->start_middle = new_start;
+ return 1;
+ }
+ if (zhdr->middle_chunks != 0 && zhdr->last_chunks != 0 &&
+ zhdr->first_chunks == 0 &&
+ zhdr->middle_chunks + zhdr->last_chunks <=
+ NCHUNKS - zhdr->start_middle - 2) {
+ unsigned short new_start = NCHUNKS - zhdr->last_chunks -
+ zhdr->middle_chunks;
+ memmove(beg + (new_start << CHUNK_SHIFT),
+ beg + (zhdr->start_middle << CHUNK_SHIFT),
+ zhdr->middle_chunks << CHUNK_SHIFT);
+ zhdr->start_middle = new_start;
+ return 1;
+ }
+ }
+out:
+ return 0;
+}
+
+static unsigned long z3fold_shrink_count(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ struct z3fold_pool *pool = container_of(shrink, struct z3fold_pool,
+ shrinker);
+
+ return atomic64_read(&pool->unbuddied_nr);
+}
+
+static unsigned long z3fold_shrink_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ struct z3fold_pool *pool = container_of(shrink, struct z3fold_pool,
+ shrinker);
+ struct z3fold_header *zhdr;
+ int i, nr_to_scan = sc->nr_to_scan, nr_shrunk = 0;
+
+ spin_lock(&pool->lock);
+ for_each_unbuddied_list_down(i, NCHUNKS - 3) {
+ if (!list_empty(&pool->unbuddied[i])) {
+ zhdr = list_first_entry(&pool->unbuddied[i],
+ struct z3fold_header, buddy);
+ list_del(&zhdr->buddy);
+ spin_unlock(&pool->lock);
+ nr_shrunk += z3fold_compact_page(zhdr, false);
+ spin_lock(&pool->lock);
+ list_add(&zhdr->buddy,
+ &pool->unbuddied[num_free_chunks(zhdr)]);
+ if (!--nr_to_scan)
+ break;
+ }
+ }
+ spin_unlock(&pool->lock);
+ return nr_shrunk;
+}
+
+
/*****************
* API Functions
*****************/
@@ -230,16 +326,27 @@ static struct z3fold_pool *z3fold_create_pool(gfp_t gfp,
pool = kzalloc(sizeof(struct z3fold_pool), gfp);
if (!pool)
- return NULL;
+ goto out;
spin_lock_init(&pool->lock);
for_each_unbuddied_list(i, 0)
INIT_LIST_HEAD(&pool->unbuddied[i]);
INIT_LIST_HEAD(&pool->buddied);
INIT_LIST_HEAD(&pool->lru);
+ pool->shrinker.count_objects = z3fold_shrink_count;
+ pool->shrinker.scan_objects = z3fold_shrink_scan;
+ pool->shrinker.seeks = DEFAULT_SEEKS;
+ pool->shrinker.batch = NCHUNKS - 4;
+ if (register_shrinker(&pool->shrinker))
+ goto out_free;
atomic64_set(&pool->pages_nr, 0);
atomic64_set(&pool->unbuddied_nr, 0);
pool->ops = ops;
return pool;
+
+out_free:
+ kfree(pool);
+out:
+ return NULL;
}
/**
@@ -250,31 +357,10 @@ static struct z3fold_pool *z3fold_create_pool(gfp_t gfp,
*/
static void z3fold_destroy_pool(struct z3fold_pool *pool)
{
+ unregister_shrinker(&pool->shrinker);
kfree(pool);
}
-/* Has to be called with lock held */
-static int z3fold_compact_page(struct z3fold_header *zhdr)
-{
- struct page *page = virt_to_page(zhdr);
- void *beg = zhdr;
-
-
- if (!test_bit(MIDDLE_CHUNK_MAPPED, &page->private) &&
- zhdr->middle_chunks != 0 &&
- zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
- memmove(beg + ZHDR_SIZE_ALIGNED,
- beg + (zhdr->start_middle << CHUNK_SHIFT),
- zhdr->middle_chunks << CHUNK_SHIFT);
- zhdr->first_chunks = zhdr->middle_chunks;
- zhdr->middle_chunks = 0;
- zhdr->start_middle = 0;
- zhdr->first_num++;
- return 1;
- }
- return 0;
-}
-
/**
* z3fold_alloc() - allocates a region of a given size
* @pool: z3fold pool from which to allocate
@@ -464,7 +550,7 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
free_z3fold_page(zhdr);
atomic64_dec(&pool->pages_nr);
} else {
- z3fold_compact_page(zhdr);
+ z3fold_compact_page(zhdr, true);
/* Add to the unbuddied list */
freechunks = num_free_chunks(zhdr);
list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
@@ -596,7 +682,7 @@ next:
/* Full, add to buddied list */
list_add(&zhdr->buddy, &pool->buddied);
} else {
- z3fold_compact_page(zhdr);
+ z3fold_compact_page(zhdr, true);
/* add to unbuddied list */
freechunks = num_free_chunks(zhdr);
list_add(&zhdr->buddy,
--
2.4.2
^ permalink raw reply [flat|nested] 4+ messages in thread