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author | Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> | 2018-04-05 16:24:43 -0700 |
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committer | Amit Pundir <amit.pundir@linaro.org> | 2018-10-04 14:17:22 +0530 |
commit | 00d3adf9f2b52139497aadcbb1a8be25acc9acb6 (patch) | |
tree | 20bd1609716377eef4cfb05ed8a3f887ab1496fe | |
parent | 49c3b184dc7d13bcd1e8ae430159750f3292d707 (diff) |
BACKPORT: zsmalloc: introduce zs_huge_class_size()
Patch series "zsmalloc/zram: drop zram's max_zpage_size", v3.
ZRAM's max_zpage_size is a bad thing. It forces zsmalloc to store
normal objects as huge ones, which results in bigger zsmalloc memory
usage. Drop it and use actual zsmalloc huge-class value when decide if
the object is huge or not.
This patch (of 2):
Not every object can be share its zspage with other objects, e.g. when
the object is as big as zspage or nearly as big a zspage. For such
objects zsmalloc has a so called huge class - every object which belongs
to huge class consumes the entire zspage (which consists of a physical
page). On x86_64, PAGE_SHIFT 12 box, the first non-huge class size is
3264, so starting down from size 3264, objects can share page(-s) and
thus minimize memory wastage.
ZRAM, however, has its own statically defined watermark for huge
objects, namely "3 * PAGE_SIZE / 4 = 3072", and forcibly stores every
object larger than this watermark (3072) as a PAGE_SIZE object, in other
words, to a huge class, while zsmalloc can keep some of those objects in
non-huge classes. This results in increased memory consumption.
zsmalloc knows better if the object is huge or not. Introduce
zs_huge_class_size() function which tells if the given object can be
stored in one of non-huge classes or not. This will let us to drop
ZRAM's huge object watermark and fully rely on zsmalloc when we decide
if the object is huge.
[sergey.senozhatsky.work@gmail.com: add pool param to zs_huge_class_size()]
Link: http://lkml.kernel.org/r/20180314081833.1096-2-sergey.senozhatsky@gmail.com
Link: http://lkml.kernel.org/r/20180306070639.7389-2-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 010b495e2fa32353d0ef6aa70a8169e5ef617a15)
Signed-off-by: Peter Kalauskas <peskal@google.com>
Bug: 113183619
Change-Id: Ic35f8c1ec75f0b78bf2d83729b6aedd2999f25c8
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
-rw-r--r-- | include/linux/zsmalloc.h | 2 | ||||
-rw-r--r-- | mm/zsmalloc.c | 43 |
2 files changed, 45 insertions, 0 deletions
diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h index 57a8e98f2708..2219cce81ca4 100644 --- a/include/linux/zsmalloc.h +++ b/include/linux/zsmalloc.h @@ -47,6 +47,8 @@ void zs_destroy_pool(struct zs_pool *pool); unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t flags); void zs_free(struct zs_pool *pool, unsigned long obj); +size_t zs_huge_class_size(struct zs_pool *pool); + void *zs_map_object(struct zs_pool *pool, unsigned long handle, enum zs_mapmode mm); void zs_unmap_object(struct zs_pool *pool, unsigned long handle); diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 8fced2101492..290e8210c13e 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -202,6 +202,7 @@ static int zs_size_classes; * (see: fix_fullness_group()) */ static const int fullness_threshold_frac = 4; +static size_t huge_class_size; struct size_class { spinlock_t lock; @@ -1351,6 +1352,25 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle) } EXPORT_SYMBOL_GPL(zs_unmap_object); +/** + * zs_huge_class_size() - Returns the size (in bytes) of the first huge + * zsmalloc &size_class. + * @pool: zsmalloc pool to use + * + * The function returns the size of the first huge class - any object of equal + * or bigger size will be stored in zspage consisting of a single physical + * page. + * + * Context: Any context. + * + * Return: the size (in bytes) of the first huge zsmalloc &size_class. + */ +size_t zs_huge_class_size(struct zs_pool *pool) +{ + return huge_class_size; +} +EXPORT_SYMBOL_GPL(zs_huge_class_size); + static unsigned long obj_malloc(struct page *first_page, struct size_class *class, unsigned long handle) { @@ -1919,12 +1939,35 @@ struct zs_pool *zs_create_pool(const char *name) for (i = zs_size_classes - 1; i >= 0; i--) { int size; int pages_per_zspage; + int objs_per_zspage; struct size_class *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); + objs_per_zspage = pages_per_zspage * PAGE_SIZE / size; + + /* + * We iterate from biggest down to smallest classes, + * so huge_class_size holds the size of the first huge + * class. Any object bigger than or equal to that will + * endup in the huge class. + */ + if (pages_per_zspage != 1 && objs_per_zspage != 1 && + !huge_class_size) { + huge_class_size = size; + /* + * The object uses ZS_HANDLE_SIZE bytes to store the + * handle. We need to subtract it, because zs_malloc() + * unconditionally adds handle size before it performs + * size class search - so object may be smaller than + * huge class size, yet it still can end up in the huge + * class because it grows by ZS_HANDLE_SIZE extra bytes + * right before class lookup. + */ + huge_class_size -= (ZS_HANDLE_SIZE - 1); + } /* * size_class is used for normal zsmalloc operation such |