From 5b52fc890bece77bffb9fade69239f71384ef02b Mon Sep 17 00:00:00 2001 From: Stephen Wilson Date: Tue, 24 May 2011 17:12:49 -0700 Subject: [PATCH] proc: allocate storage for numa_maps statistics once 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 Reviewed-by: KOSAKI Motohiro Cc: Hugh Dickins Cc: David Rientjes Cc: Lee Schermerhorn Cc: Alexey Dobriyan Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 36 +++++++++++++++++++++++++++--------- 1 file changed, 27 insertions(+), 9 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 2ed53d18b2e..2c9db29ea35 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -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 = { -- 2.20.1