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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: KOSAKI 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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1 parent 692e0b3 commit de03c72cfce5b263a674d04348b58475ec50163c @kosaki kosaki committed with torvalds May 24, 2011
Showing with 44 additions and 9 deletions.
  1. +1 −1 Documentation/cachetlb.txt
  2. +0 −1 arch/x86/kernel/tboot.c
  3. +6 −3 include/linux/mm_types.h
  4. +1 −0 include/linux/sched.h
  5. +2 −0 init/main.c
  6. +34 −3 kernel/fork.c
  7. +0 −1 mm/init-mm.c
View
2 Documentation/cachetlb.txt
@@ -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
View
1 arch/x86/kernel/tboot.c
@@ -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)
View
9 include/linux/mm_types.h
@@ -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 */
View
1 include/linux/sched.h
@@ -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 *);
View
2 init/main.c
@@ -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()
View
37 kernel/fork.c
@@ -485,6 +485,20 @@ static void mm_init_aio(struct mm_struct *mm)
#endif
}
+int mm_init_cpumask(struct mm_struct *mm, struct mm_struct *oldmm)
+{
+#ifdef CONFIG_CPUMASK_OFFSTACK
+ if (!alloc_cpumask_var(&mm->cpu_vm_mask_var, GFP_KERNEL))
+ return -ENOMEM;
+
+ if (oldmm)
+ cpumask_copy(mm_cpumask(mm), mm_cpumask(oldmm));
+ else
+ memset(mm_cpumask(mm), 0, cpumask_size());
+#endif
+ return 0;
+}
+
static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
{
atomic_set(&mm->mm_users, 1);
@@ -521,10 +535,20 @@ struct mm_struct * mm_alloc(void)
struct mm_struct * mm;
mm = allocate_mm();
- if (mm) {
- memset(mm, 0, sizeof(*mm));
- mm = mm_init(mm, current);
+ if (!mm)
+ return NULL;
+
+ memset(mm, 0, sizeof(*mm));
+ mm = mm_init(mm, current);
+ if (!mm)
+ return NULL;
+
+ if (mm_init_cpumask(mm, NULL)) {
+ mm_free_pgd(mm);
+ free_mm(mm);
+ return NULL;
}
+
return mm;
}
@@ -536,6 +560,7 @@ struct mm_struct * mm_alloc(void)
void __mmdrop(struct mm_struct *mm)
{
BUG_ON(mm == &init_mm);
+ free_cpumask_var(mm->cpu_vm_mask_var);
mm_free_pgd(mm);
destroy_context(mm);
mmu_notifier_mm_destroy(mm);
@@ -690,6 +715,9 @@ struct mm_struct *dup_mm(struct task_struct *tsk)
if (!mm_init(mm, tsk))
goto fail_nomem;
+ if (mm_init_cpumask(mm, oldmm))
+ goto fail_nocpumask;
+
if (init_new_context(tsk, mm))
goto fail_nocontext;
@@ -716,6 +744,9 @@ struct mm_struct *dup_mm(struct task_struct *tsk)
return NULL;
fail_nocontext:
+ free_cpumask_var(mm->cpu_vm_mask_var);
+
+fail_nocpumask:
/*
* If init_new_context() failed, we cannot use mmput() to free the mm
* because it calls destroy_context()
View
1 mm/init-mm.c
@@ -21,6 +21,5 @@ struct mm_struct init_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,
INIT_MM_CONTEXT(init_mm)
};

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