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Commit 481b4bb5 authored by Richard Kennedy's avatar Richard Kennedy Committed by Linus Torvalds
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mm: mm_struct: remove 16 bytes of alignment padding on 64 bit builds 



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: default avatarRichard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cb240452

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. */