mm: mm_struct: remove 16 bytes of alignment padding on 64 bit builds (481b4bb5) · Commits · 戴 / test

Reorder mm_struct to remove 16 bytes of alignment padding on 64 bit builds. On my config this shrinks mm_struct by enough to fit in one fewer cache lines and allows more objects per slab in mm_struct kmem_cache under SLUB. slabinfo before patch :- Sizes (bytes) Slabs -------------------------------- Object : 848 Total : 9 SlabObj: 896 Full : 2 SlabSiz: 16384 Partial: 5 Loss : 48 CpuSlab: 2 Align : 64 Objects: 18 slabinfo after :- Sizes (bytes) Slabs -------------------------------- Object : 832 Total : 7 SlabObj: 832 Full : 2 SlabSiz: 16384 Partial: 3 Loss : 0 CpuSlab: 2 Align : 64 Objects: 19 Signed-off-by:

Richard Kennedy <richard@rsk.demon.co.uk> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm_types.h

+5 −3

Original line number	Diff line number	Diff line
		@@ -237,8 +237,9 @@ struct mm_struct {
		atomic_t mm_users; /* How many users with user space? */
		atomic_t mm_count; /* How many references to "struct mm_struct" (users count as 1) */
		int map_count; /* number of VMAs */
		struct rw_semaphore mmap_sem;

		spinlock_t page_table_lock; /* Protects page tables and some counters */
		struct rw_semaphore mmap_sem;

		struct list_head mmlist; /* List of maybe swapped mm's. These are globally strung
		* together off init_mm.mmlist, and are protected
		@@ -281,6 +282,9 @@ struct mm_struct {
		unsigned int token_priority;
		unsigned int last_interval;

		/* How many tasks sharing this mm are OOM_DISABLE */
		atomic_t oom_disable_count;

		unsigned long flags; /* Must use atomic bitops to access the bits */

		struct core_state core_state; / coredumping support */
		@@ -313,8 +317,6 @@ struct mm_struct {
		#ifdef CONFIG_TRANSPARENT_HUGEPAGE
		pgtable_t pmd_huge_pte; /* protected by page_table_lock */
		#endif
		/* How many tasks sharing this mm are OOM_DISABLE */
		atomic_t oom_disable_count;
		};

		/* Future-safe accessor for struct mm_struct's cpu_vm_mask. */

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