aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorJoonsoo Kim <iamjoonsoo.kim@lge.com>2014-12-12 16:56:44 -0800
committerAlex Shi <alex.shi@linaro.org>2015-05-11 21:31:03 +0800
commit48eaa2e2b66fffbfa6eefa46c34cfbf47ccc1fce (patch)
treedfe7c4b40f3d03cffc333776b0273a61da3347fc
parent7aecdc886e2e9bacfaf2377067072fa63d649b21 (diff)
downloadlinux-linaro-stable-48eaa2e2b66fffbfa6eefa46c34cfbf47ccc1fce.tar.gz
zsmalloc: merge size_class to reduce fragmentation
zsmalloc has many size_classes to reduce fragmentation and they are in 16 bytes unit, for example, 16, 32, 48, etc., if PAGE_SIZE is 4096. And, zsmalloc has constraint that each zspage has 4 pages at maximum. In this situation, we can see interesting aspect. Let's think about size_class for 1488, 1472, ..., 1376. To prevent external fragmentation, they uses 4 pages per zspage and so all they can contain 11 objects at maximum. 16384 (4096 * 4) = 1488 * 11 + remains 16384 (4096 * 4) = 1472 * 11 + remains 16384 (4096 * 4) = ... 16384 (4096 * 4) = 1376 * 11 + remains It means that they have same characteristics and classification between them isn't needed. If we use one size_class for them, we can reduce fragementation and save some memory since both the 1488 and 1472 sized classes can only fit 11 objects into 4 pages, and an object that's 1472 bytes can fit into an object that's 1488 bytes, merging these classes to always use objects that are 1488 bytes will reduce the total number of size classes. And reducing the total number of size classes reduces overall fragmentation, because a wider range of compressed pages can fit into a single size class, leaving less unused objects in each size class. For this purpose, this patch implement size_class merging. If there is size_class that have same pages_per_zspage and same number of objects per zspage with previous size_class, we don't create new size_class. Instead, we use previous, same characteristic size_class. With this way, above example sizes (1488, 1472, ..., 1376) use just one size_class so we can get much more memory utilization. Below is result of my simple test. TEST ENV: EXT4 on zram, mount with discard option WORKLOAD: untar kernel source code, remove directory in descending order in size. (drivers arch fs sound include net Documentation firmware kernel tools) Each line represents orig_data_size, compr_data_size, mem_used_total, fragmentation overhead (mem_used - compr_data_size) and overhead ratio (overhead to compr_data_size), respectively, after untar and remove operation is executed. * untar-nomerge.out orig_size compr_size used_size overhead overhead_ratio 525.88MB 199.16MB 210.23MB 11.08MB 5.56% 288.32MB 97.43MB 105.63MB 8.20MB 8.41% 177.32MB 61.12MB 69.40MB 8.28MB 13.55% 146.47MB 47.32MB 56.10MB 8.78MB 18.55% 124.16MB 38.85MB 48.41MB 9.55MB 24.58% 103.93MB 31.68MB 40.93MB 9.25MB 29.21% 84.34MB 22.86MB 32.72MB 9.86MB 43.13% 66.87MB 14.83MB 23.83MB 9.00MB 60.70% 60.67MB 11.11MB 18.60MB 7.49MB 67.48% 55.86MB 8.83MB 16.61MB 7.77MB 88.03% 53.32MB 8.01MB 15.32MB 7.31MB 91.24% * untar-merge.out orig_size compr_size used_size overhead overhead_ratio 526.23MB 199.18MB 209.81MB 10.64MB 5.34% 288.68MB 97.45MB 104.08MB 6.63MB 6.80% 177.68MB 61.14MB 66.93MB 5.79MB 9.47% 146.83MB 47.34MB 52.79MB 5.45MB 11.51% 124.52MB 38.87MB 44.30MB 5.43MB 13.96% 104.29MB 31.70MB 36.83MB 5.13MB 16.19% 84.70MB 22.88MB 27.92MB 5.04MB 22.04% 67.11MB 14.83MB 19.26MB 4.43MB 29.86% 60.82MB 11.10MB 14.90MB 3.79MB 34.17% 55.90MB 8.82MB 12.61MB 3.79MB 42.97% 53.32MB 8.01MB 11.73MB 3.73MB 46.53% As you can see above result, merged one has better utilization (overhead ratio, 5th column) and uses less memory (mem_used_total, 3rd column). Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Nitin Gupta <ngupta@vflare.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reviewed-by: Dan Streetman <ddstreet@ieee.org> Cc: Luigi Semenzato <semenzato@google.com> Cc: <juno.choi@lge.com> Cc: "seungho1.park" <seungho1.park@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> (cherry picked from commit 9eec4cd53f9865b733dc78cf5f6465871beed014) Signed-off-by: Alex Shi <alex.shi@linaro.org>
-rw-r--r--mm/zsmalloc.c80
1 files changed, 66 insertions, 14 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 00c28039b06a..91eac3cf17e8 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -202,7 +202,7 @@ struct link_free {
};
struct zs_pool {
- struct size_class size_class[ZS_SIZE_CLASSES];
+ struct size_class *size_class[ZS_SIZE_CLASSES];
gfp_t flags; /* allocation flags used when growing pool */
atomic_long_t pages_allocated;
@@ -434,7 +434,7 @@ static enum fullness_group fix_fullness_group(struct zs_pool *pool,
if (newfg == currfg)
goto out;
- class = &pool->size_class[class_idx];
+ class = pool->size_class[class_idx];
remove_zspage(page, class, currfg);
insert_zspage(page, class, newfg);
set_zspage_mapping(page, class_idx, newfg);
@@ -891,6 +891,23 @@ fail:
return notifier_to_errno(ret);
}
+static unsigned int get_maxobj_per_zspage(int size, int pages_per_zspage)
+{
+ return pages_per_zspage * PAGE_SIZE / size;
+}
+
+static bool can_merge(struct size_class *prev, int size, int pages_per_zspage)
+{
+ if (prev->pages_per_zspage != pages_per_zspage)
+ return false;
+
+ if (get_maxobj_per_zspage(prev->size, prev->pages_per_zspage)
+ != get_maxobj_per_zspage(size, pages_per_zspage))
+ return false;
+
+ return true;
+}
+
/**
* zs_create_pool - Creates an allocation pool to work from.
* @flags: allocation flags used to allocate pool metadata
@@ -911,25 +928,56 @@ struct zs_pool *zs_create_pool(gfp_t flags)
if (!pool)
return NULL;
- for (i = 0; i < ZS_SIZE_CLASSES; i++) {
+ /*
+ * Iterate reversly, because, size of size_class that we want to use
+ * for merging should be larger or equal to current size.
+ */
+ for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
int size;
+ int pages_per_zspage;
struct size_class *class;
+ struct size_class *prev_class;
size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
if (size > ZS_MAX_ALLOC_SIZE)
size = ZS_MAX_ALLOC_SIZE;
+ pages_per_zspage = get_pages_per_zspage(size);
+
+ /*
+ * size_class is used for normal zsmalloc operation such
+ * as alloc/free for that size. Although it is natural that we
+ * have one size_class for each size, there is a chance that we
+ * can get more memory utilization if we use one size_class for
+ * many different sizes whose size_class have same
+ * characteristics. So, we makes size_class point to
+ * previous size_class if possible.
+ */
+ if (i < ZS_SIZE_CLASSES - 1) {
+ prev_class = pool->size_class[i + 1];
+ if (can_merge(prev_class, size, pages_per_zspage)) {
+ pool->size_class[i] = prev_class;
+ continue;
+ }
+ }
+
+ class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
+ if (!class)
+ goto err;
- class = &pool->size_class[i];
class->size = size;
class->index = i;
+ class->pages_per_zspage = pages_per_zspage;
spin_lock_init(&class->lock);
- class->pages_per_zspage = get_pages_per_zspage(size);
-
+ pool->size_class[i] = class;
}
pool->flags = flags;
return pool;
+
+err:
+ zs_destroy_pool(pool);
+ return NULL;
}
EXPORT_SYMBOL_GPL(zs_create_pool);
@@ -939,7 +987,13 @@ void zs_destroy_pool(struct zs_pool *pool)
for (i = 0; i < ZS_SIZE_CLASSES; i++) {
int fg;
- struct size_class *class = &pool->size_class[i];
+ struct size_class *class = pool->size_class[i];
+
+ if (!class)
+ continue;
+
+ if (class->index != i)
+ continue;
for (fg = 0; fg < _ZS_NR_FULLNESS_GROUPS; fg++) {
if (class->fullness_list[fg]) {
@@ -948,6 +1002,7 @@ void zs_destroy_pool(struct zs_pool *pool)
class->size, fg);
}
}
+ kfree(class);
}
kfree(pool);
}
@@ -966,7 +1021,6 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
{
unsigned long obj;
struct link_free *link;
- int class_idx;
struct size_class *class;
struct page *first_page, *m_page;
@@ -975,9 +1029,7 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
return 0;
- class_idx = get_size_class_index(size);
- class = &pool->size_class[class_idx];
- BUG_ON(class_idx != class->index);
+ class = pool->size_class[get_size_class_index(size)];
spin_lock(&class->lock);
first_page = find_get_zspage(class);
@@ -1030,7 +1082,7 @@ void zs_free(struct zs_pool *pool, unsigned long obj)
first_page = get_first_page(f_page);
get_zspage_mapping(first_page, &class_idx, &fullness);
- class = &pool->size_class[class_idx];
+ class = pool->size_class[class_idx];
f_offset = obj_idx_to_offset(f_page, f_objidx, class->size);
spin_lock(&class->lock);
@@ -1091,7 +1143,7 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
obj_handle_to_location(handle, &page, &obj_idx);
get_zspage_mapping(get_first_page(page), &class_idx, &fg);
- class = &pool->size_class[class_idx];
+ class = pool->size_class[class_idx];
off = obj_idx_to_offset(page, obj_idx, class->size);
area = &get_cpu_var(zs_map_area);
@@ -1125,7 +1177,7 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
obj_handle_to_location(handle, &page, &obj_idx);
get_zspage_mapping(get_first_page(page), &class_idx, &fg);
- class = &pool->size_class[class_idx];
+ class = pool->size_class[class_idx];
off = obj_idx_to_offset(page, obj_idx, class->size);
area = &__get_cpu_var(zs_map_area);