From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id B5AE16B0008 for ; Tue, 6 Mar 2018 02:06:55 -0500 (EST) Received: by mail-pg0-f72.google.com with SMTP id k62so8369161pgd.11 for ; Mon, 05 Mar 2018 23:06:55 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id t4-v6sor4573278plb.45.2018.03.05.23.06.54 for (Google Transport Security); Mon, 05 Mar 2018 23:06:54 -0800 (PST) From: Sergey Senozhatsky Subject: [PATCHv2 1/2] zsmalloc: introduce zs_huge_class_size() function Date: Tue, 6 Mar 2018 16:06:38 +0900 Message-Id: <20180306070639.7389-2-sergey.senozhatsky@gmail.com> In-Reply-To: <20180306070639.7389-1-sergey.senozhatsky@gmail.com> References: <20180306070639.7389-1-sergey.senozhatsky@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sergey Senozhatsky , Sergey Senozhatsky , Mike Rapoport 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 - "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. Signed-off-by: Sergey Senozhatsky --- include/linux/zsmalloc.h | 2 ++ mm/zsmalloc.c | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h index 57a8e98f2708..753c1af4d2cb 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(void); + 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 a583ab111a43..63422cf35b94 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -193,6 +193,7 @@ static struct vfsmount *zsmalloc_mnt; * (see: fix_fullness_group()) */ static const int fullness_threshold_frac = 4; +static size_t huge_class_size; struct size_class { spinlock_t lock; @@ -1407,6 +1408,24 @@ 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. + * + * 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(void) +{ + return huge_class_size; +} +EXPORT_SYMBOL_GPL(zs_huge_class_size); + static unsigned long obj_malloc(struct size_class *class, struct zspage *zspage, unsigned long handle) { @@ -2363,6 +2382,27 @@ struct zs_pool *zs_create_pool(const char *name) 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 * as alloc/free for that size. Although it is natural that we -- 2.16.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org