From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 845836B02ED for ; Wed, 7 Feb 2018 04:29:37 -0500 (EST) Received: by mail-pf0-f199.google.com with SMTP id a9so146151pff.0 for ; Wed, 07 Feb 2018 01:29:37 -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 l1-v6sor378301pld.49.2018.02.07.01.29.36 for (Google Transport Security); Wed, 07 Feb 2018 01:29:36 -0800 (PST) From: Sergey Senozhatsky Subject: [PATCH 1/2] zsmalloc: introduce zs_huge_object() function Date: Wed, 7 Feb 2018 18:29:18 +0900 Message-Id: <20180207092919.19696-2-sergey.senozhatsky@gmail.com> In-Reply-To: <20180207092919.19696-1-sergey.senozhatsky@gmail.com> References: <20180207092919.19696-1-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 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_object() 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 | 17 +++++++++++++++++ 2 files changed, 19 insertions(+) diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h index 57a8e98f2708..9a1baf673cc1 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); +bool zs_huge_object(size_t sz); + 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 c3013505c305..b3e295a806be 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -192,6 +192,7 @@ static struct vfsmount *zsmalloc_mnt; * (see: fix_fullness_group()) */ static const int fullness_threshold_frac = 4; +static size_t zs_huge_class_size; struct size_class { spinlock_t lock; @@ -1417,6 +1418,19 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle) } EXPORT_SYMBOL_GPL(zs_unmap_object); +/* + * Check if the object's size falls into huge_class area. We must take + * ZS_HANDLE_SIZE into account and test the actual size we are going to + * use up. zs_malloc() unconditionally adds handle size before it performs + * size_class lookup, so we may endup in a huge class yet zs_huge_object() + * returned 'false'. + */ +bool zs_huge_object(size_t sz) +{ + return sz + ZS_HANDLE_SIZE >= zs_huge_class_size; +} +EXPORT_SYMBOL_GPL(zs_huge_object); + static unsigned long obj_malloc(struct size_class *class, struct zspage *zspage, unsigned long handle) { @@ -2404,6 +2418,9 @@ struct zs_pool *zs_create_pool(const char *name) INIT_LIST_HEAD(&class->fullness_list[fullness]); prev_class = class; + if (pages_per_zspage == 1 && objs_per_zspage == 1 + && !zs_huge_class_size) + zs_huge_class_size = size; } /* debug only, don't abort if it fails */ -- 2.16.1 -- 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