From 26e93839d6d9d9c6169fa7559b8d1577e42d4ace Mon Sep 17 00:00:00 2001 From: Chengming Zhou Date: Wed, 28 Feb 2024 02:38:54 +0000 Subject: [PATCH] mm/zsmalloc: don't need to reserve LSB in handle We will save allocated tag in the object header to indicate that it's allocated. handle |= OBJ_ALLOCATED_TAG; So the object header needs to reserve LSB for this tag bit. But the handle itself doesn't need to reserve LSB to save tag, since it's only used to find the position of object, by (pfn + obj_idx). So remove LSB reserve from handle, one more bit can be used as obj_idx. Link: https://lkml.kernel.org/r/20240228023854.3511239-1-chengming.zhou@linux.dev Signed-off-by: Chengming Zhou Reviewed-by: Sergey Senozhatsky Cc: Johannes Weiner Cc: Minchan Kim Cc: Nhat Pham Cc: Yosry Ahmed Signed-off-by: Andrew Morton --- mm/zsmalloc.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 63ec385cd670..7d7cb3eaabe0 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -110,7 +110,7 @@ #define OBJ_TAG_BITS 1 #define OBJ_TAG_MASK OBJ_ALLOCATED_TAG -#define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS) +#define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_BITS) #define OBJ_INDEX_MASK ((_AC(1, UL) << OBJ_INDEX_BITS) - 1) #define HUGE_BITS 1 @@ -737,14 +737,12 @@ static struct page *get_next_page(struct page *page) static void obj_to_location(unsigned long obj, struct page **page, unsigned int *obj_idx) { - obj >>= OBJ_TAG_BITS; *page = pfn_to_page(obj >> OBJ_INDEX_BITS); *obj_idx = (obj & OBJ_INDEX_MASK); } static void obj_to_page(unsigned long obj, struct page **page) { - obj >>= OBJ_TAG_BITS; *page = pfn_to_page(obj >> OBJ_INDEX_BITS); } @@ -759,7 +757,6 @@ static unsigned long location_to_obj(struct page *page, unsigned int obj_idx) obj = page_to_pfn(page) << OBJ_INDEX_BITS; obj |= obj_idx & OBJ_INDEX_MASK; - obj <<= OBJ_TAG_BITS; return obj; }