diff options
| -rw-r--r-- | include/linux/mm_types.h | 27 |
1 files changed, 20 insertions, 7 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5aacc1c10a45..8f0fb62e8975 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -445,13 +445,6 @@ struct mm_struct { */ atomic_t has_pinned; - /** - * @write_protect_seq: Locked when any thread is write - * protecting pages mapped by this mm to enforce a later COW, - * for instance during page table copying for fork(). - */ - seqcount_t write_protect_seq; - #ifdef CONFIG_MMU atomic_long_t pgtables_bytes; /* PTE page table pages */ #endif @@ -460,6 +453,18 @@ struct mm_struct { spinlock_t page_table_lock; /* Protects page tables and some * counters */ + /* + * With some kernel config, the current mmap_lock's offset + * inside 'mm_struct' is at 0x120, which is very optimal, as + * its two hot fields 'count' and 'owner' sit in 2 different + * cachelines, and when mmap_lock is highly contended, both + * of the 2 fields will be accessed frequently, current layout + * will help to reduce cache bouncing. + * + * So please be careful with adding new fields before + * mmap_lock, which can easily push the 2 fields into one + * cacheline. + */ struct rw_semaphore mmap_lock; struct list_head mmlist; /* List of maybe swapped mm's. These @@ -480,7 +485,15 @@ struct mm_struct { unsigned long stack_vm; /* VM_STACK */ unsigned long def_flags; + /** + * @write_protect_seq: Locked when any thread is write + * protecting pages mapped by this mm to enforce a later COW, + * for instance during page table copying for fork(). + */ + seqcount_t write_protect_seq; + spinlock_t arg_lock; /* protect the below fields */ + unsigned long start_code, end_code, start_data, end_data; unsigned long start_brk, brk, start_stack; unsigned long arg_start, arg_end, env_start, env_end; |