From 010b495e2fa32353d0ef6aa70a8169e5ef617a15 Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Thu, 5 Apr 2018 16:24:43 -0700 Subject: 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 Acked-by: Minchan Kim Cc: Mike Rapoport Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/zsmalloc.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/zsmalloc.h') 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); -- cgit