Commit de03c72c authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds
Browse files

mm: convert mm->cpu_vm_cpumask into cpumask_var_t 



cpumask_t is very big struct and cpu_vm_mask is placed wrong position.
It might lead to reduce cache hit ratio.

This patch has two change.
1) Move the place of cpumask into last of mm_struct. Because usually cpumask
   is accessed only front bits when the system has cpu-hotplug capability
2) Convert cpu_vm_mask into cpumask_var_t. It may help to reduce memory
   footprint if cpumask_size() will use nr_cpumask_bits properly in future.

In addition, this patch change the name of cpu_vm_mask with cpu_vm_mask_var.
It may help to detect out of tree cpu_vm_mask users.

This patch has no functional change.

[akpm@linux-foundation.org: build fix]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 692e0b35

Documentation/cachetlb.txt

+1 −1
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ on all processors in the system. Don't let this scare you into 
thinking SMP cache/tlb flushing must be so inefficient, this is in

fact an area where many optimizations are possible.  For example,

if it can be proven that a user address space has never executed

on a cpu (see vma->cpu_vm_mask), one need not perform a flush

on a cpu (see mm_cpumask()), one need not perform a flush

for this address space on that cpu.



First, the TLB flushing interfaces, since they are the simplest.  The

arch/x86/kernel/tboot.c

+0 −1
Original line number Diff line number Diff line
@@ -110,7 +110,6 @@ static struct mm_struct tboot_mm = { 
	.mmap_sem       = __RWSEM_INITIALIZER(init_mm.mmap_sem),

	.page_table_lock =  __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),

	.mmlist         = LIST_HEAD_INIT(init_mm.mmlist),

	.cpu_vm_mask    = CPU_MASK_ALL,

};



static inline void switch_to_tboot_pt(void)

include/linux/mm_types.h

+6 −3
Original line number Diff line number Diff line
@@ -265,8 +265,6 @@ struct mm_struct { 


	struct linux_binfmt *binfmt;



	cpumask_t cpu_vm_mask;



	/* Architecture-specific MM context */

	mm_context_t context;
@@ -316,9 +314,14 @@ struct mm_struct { 
#ifdef CONFIG_TRANSPARENT_HUGEPAGE

	pgtable_t pmd_huge_pte; /* protected by page_table_lock */

#endif



	cpumask_var_t cpu_vm_mask_var;

};



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

#define mm_cpumask(mm) (&(mm)->cpu_vm_mask)

static inline cpumask_t *mm_cpumask(struct mm_struct *mm)

{

	return mm->cpu_vm_mask_var;

}



#endif /* _LINUX_MM_TYPES_H */

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -2176,6 +2176,7 @@ static inline void mmdrop(struct mm_struct * mm) 
	if (unlikely(atomic_dec_and_test(&mm->mm_count)))

		__mmdrop(mm);

}

extern int mm_init_cpumask(struct mm_struct *mm, struct mm_struct *oldmm);



/* mmput gets rid of the mappings and all user-space */

extern void mmput(struct mm_struct *);

init/main.c

+2 −0
Original line number Diff line number Diff line
@@ -509,6 +509,8 @@ asmlinkage void __init start_kernel(void) 
	sort_main_extable();

	trap_init();

	mm_init();

	BUG_ON(mm_init_cpumask(&init_mm, 0));



	/*

	 * Set up the scheduler prior starting any interrupts (such as the

	 * timer interrupt). Full topology setup happens at smp_init()

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