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proc: allocate storage for numa_maps statistics once

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In show_numa_map() we collect statistics into a numa_maps structure.
Since the number of NUMA nodes can be very large, this structure is not a
candidate for stack allocation.

Instead of going thru a kmalloc()+kfree() cycle each time show_numa_map()
is invoked, perform the allocation just once when /proc/pid/numa_maps is
opened.

Performing the allocation when numa_maps is opened, and thus before a
reference to the target tasks mm is taken, eliminates a potential
stalemate condition in the oom-killer as originally described by Hugh
Dickins:

  ... imagine what happens if the system is out of memory, and the mm
  we're looking at is selected for killing by the OOM killer: while
  we wait in __get_free_page for more memory, no memory is freed
  from the selected mm because it cannot reach exit_mmap while we hold
  that reference.

Signed-off-by: Stephen Wilson <wilsons@start.ca>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Stephen Wilson 2011-05-24 17:12:49 -07:00 committed by Linus Torvalds
parent f2beb79836
commit 5b52fc890b
1 changed files with 27 additions and 9 deletions
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36
fs/proc/task_mmu.c
View file

@ -871,6 +871,11 @@ struct numa_maps {
unsigned long node[MAX_NUMNODES];
};
struct numa_maps_private {
struct proc_maps_private proc_maps;
struct numa_maps md;
};
static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty)
{
int count = page_mapcount(page);
@ -963,9 +968,10 @@ static int gather_hugetbl_stats(pte_t *pte, unsigned long hmask,
*/
static int show_numa_map(struct seq_file *m, void *v)
{
struct proc_maps_private *priv = m->private;
struct numa_maps_private *numa_priv = m->private;
struct proc_maps_private *proc_priv = &numa_priv->proc_maps;
struct vm_area_struct *vma = v;
struct numa_maps *md;
struct numa_maps *md = &numa_priv->md;
struct file *file = vma->vm_file;
struct mm_struct *mm = vma->vm_mm;
struct mm_walk walk = {};
@ -976,9 +982,8 @@ static int show_numa_map(struct seq_file *m, void *v)
if (!mm)
return 0;
md = kzalloc(sizeof(struct numa_maps), GFP_KERNEL);
if (!md)
return 0;
/* Ensure we start with an empty set of numa_maps statistics. */
memset(md, 0, sizeof(*md));
md->vma = vma;
@ -987,7 +992,7 @@ static int show_numa_map(struct seq_file *m, void *v)
walk.private = md;
walk.mm = mm;
pol = get_vma_policy(priv->task, vma, vma->vm_start);
pol = get_vma_policy(proc_priv->task, vma, vma->vm_start);
mpol_to_str(buffer, sizeof(buffer), pol, 0);
mpol_cond_put(pol);
@ -1034,12 +1039,12 @@ static int show_numa_map(struct seq_file *m, void *v)
seq_printf(m, " N%d=%lu", n, md->node[n]);
out:
seq_putc(m, '\n');
kfree(md);
if (m->count < m->size)
m->version = (vma != priv->tail_vma) ? vma->vm_start : 0;
m->version = (vma != proc_priv->tail_vma) ? vma->vm_start : 0;
return 0;
}
static const struct seq_operations proc_pid_numa_maps_op = {
.start = m_start,
.next = m_next,
@ -1049,7 +1054,20 @@ static const struct seq_operations proc_pid_numa_maps_op = {
static int numa_maps_open(struct inode *inode, struct file *file)
{
return do_maps_open(inode, file, &proc_pid_numa_maps_op);
struct numa_maps_private *priv;
int ret = -ENOMEM;
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (priv) {
priv->proc_maps.pid = proc_pid(inode);
ret = seq_open(file, &proc_pid_numa_maps_op);
if (!ret) {
struct seq_file *m = file->private_data;
m->private = priv;
} else {
kfree(priv);
}
}
return ret;
}
const struct file_operations proc_numa_maps_operations = {