From: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
zsmalloc knows the watermark after which classes are considered
to be ->huge -- every object stored consumes the entire zspage (which
consist of a single order-0 page). On x86_64, PAGE_SHIFT 12 box, the
first non-huge class size is 3264, so starting down from size 3264,
objects share page(-s) and thus minimize memory wastage.
zram, however, has its own statically defined watermark for `bad'
compression "3 * PAGE_SIZE / 4 = 3072", and stores every object
larger than this watermark (3072) as a PAGE_SIZE, object, IOW,
to a ->huge class, this results in increased memory consumption and
memory wastage. (With a small exception: 3264 bytes class. zs_malloc()
adds ZS_HANDLE_SIZE to the object's size, so some objects can pass
3072 bytes and get_size_class_index(size) will return 3264 bytes size
class).
Introduce a zs_get_huge_class_size_watermark() function which tells
the size of a first non-huge class; so zram now can store objects
to ->huge clases only when those objects have sizes greater than
huge_class_size_watermark.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
include/linux/zsmalloc.h | 2 ++
mm/zsmalloc.c | 14 ++++++++++++++
2 files changed, 16 insertions(+)
diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
index 34eb160..45dcb51 100644
--- a/include/linux/zsmalloc.h
+++ b/include/linux/zsmalloc.h
@@ -55,4 +55,6 @@ unsigned long zs_get_total_pages(struct zs_pool *pool);
unsigned long zs_compact(struct zs_pool *pool);
void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats);
+
+int zs_get_huge_class_size_watermark(void);
#endif
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 43e4cbc..e7f10bd 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -188,6 +188,11 @@ static struct dentry *zs_stat_root;
static int zs_size_classes;
/*
+ * All classes above this class_size are huge classes
+ */
+static int huge_class_size_watermark;
+
+/*
* We assign a page to ZS_ALMOST_EMPTY fullness group when:
* n <= N / f, where
* n = number of allocated objects
@@ -1241,6 +1246,12 @@ unsigned long zs_get_total_pages(struct zs_pool *pool)
}
EXPORT_SYMBOL_GPL(zs_get_total_pages);
+int zs_get_huge_class_size_watermark(void)
+{
+ return huge_class_size_watermark;
+}
+EXPORT_SYMBOL_GPL(zs_get_huge_class_size_watermark);
+
/**
* zs_map_object - get address of allocated object from handle.
* @pool: pool from which the object was allocated
@@ -1942,10 +1953,13 @@ struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
if (pages_per_zspage == 1 &&
get_maxobj_per_zspage(size, pages_per_zspage) == 1)
class->huge = true;
+
spin_lock_init(&class->lock);
pool->size_class[i] = class;
prev_class = class;
+ if (!class->huge && !huge_class_size_watermark)
+ huge_class_size_watermark = size - ZS_HANDLE_SIZE;
}
pool->flags = flags;
--
2.7.1
--
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