Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760330Ab1D0XiI (ORCPT ); Wed, 27 Apr 2011 19:38:08 -0400 Received: from mout.perfora.net ([74.208.4.194]:49952 "EHLO mout.perfora.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760320Ab1D0XiE (ORCPT ); Wed, 27 Apr 2011 19:38:04 -0400 From: Stephen Wilson To: Andrew Morton Cc: Alexander Viro , KOSAKI Motohiro , Hugh Dickins , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 8/8] proc: allocate storage for numa_maps statistics once Date: Wed, 27 Apr 2011 19:35:49 -0400 Message-Id: <1303947349-3620-9-git-send-email-wilsons@start.ca> X-Mailer: git-send-email 1.7.3.5 In-Reply-To: <1303947349-3620-1-git-send-email-wilsons@start.ca> References: <1303947349-3620-1-git-send-email-wilsons@start.ca> X-Provags-ID: V02:K0:vP8tTsLg37Ze7I6DaPUq8uJ5o8/AnCdR0O3881FIhAu PiHN5qSlPQ2iRgts94GXLoz2GG5voT5LvazTAReEiMyyucd2SU hMKex6r0Jj47I8exoncYTEIh9t2b47K5zxB4MGP9vvDO5a51dD b7/riMUX7CfIgic4uuRTTDYp/xrBWd21pjdVOUfiAhln2xOeR4 9vwODijx0wWTq80m+KF6+c3B06RQHQvD10F6kpCnJk= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3872 Lines: 118 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 --- fs/proc/task_mmu.c | 36 +++++++++++++++++++++++++++--------- 1 files changed, 27 insertions(+), 9 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 9f069d2..1ca3a00 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -868,6 +868,11 @@ 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); @@ -949,9 +954,10 @@ 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 = {}; @@ -962,16 +968,15 @@ 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)); walk.hugetlb_entry = gather_hugetbl_stats; walk.pte_entry = gather_pte_stats; 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); @@ -1018,12 +1023,12 @@ 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, @@ -1033,7 +1038,20 @@ 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 = { -- 1.7.3.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/