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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: 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>
This commit is contained in:
Richard Kennedy 2011-03-22 16:32:50 -07:00 committed by Linus Torvalds
parent cb240452bf
commit 481b4bb5e3
1 changed files with 5 additions and 3 deletions
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8
include/linux/mm_types.h
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@ -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. */