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authorJohannes Weiner <hannes@cmpxchg.org>2016-02-03 03:57:29 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-02-03 19:28:43 +0300
commit65376df582174ffcec9e6471bf5b0dd79ba05e4a (patch)
tree60c4841a00605605bf8c315783ed48648333e865 /fs/proc/task_mmu.c
parent5c2ff95e41c9290d16556cd02e35b25d81be8fe0 (diff)
downloadlinux-65376df582174ffcec9e6471bf5b0dd79ba05e4a.tar.xz
proc: revert /proc/<pid>/maps [stack:TID] annotation
Commit b76437579d13 ("procfs: mark thread stack correctly in proc/<pid>/maps") added [stack:TID] annotation to /proc/<pid>/maps. Finding the task of a stack VMA requires walking the entire thread list, turning this into quadratic behavior: a thousand threads means a thousand stacks, so the rendering of /proc/<pid>/maps needs to look at a million combinations. The cost is not in proportion to the usefulness as described in the patch. Drop the [stack:TID] annotation to make /proc/<pid>/maps (and /proc/<pid>/numa_maps) usable again for higher thread counts. The [stack] annotation inside /proc/<pid>/task/<tid>/maps is retained, as identifying the stack VMA there is an O(1) operation. Siddesh said: "The end users needed a way to identify thread stacks programmatically and there wasn't a way to do that. I'm afraid I no longer remember (or have access to the resources that would aid my memory since I changed employers) the details of their requirement. However, I did do this on my own time because I thought it was an interesting project for me and nobody really gave any feedback then as to its utility, so as far as I am concerned you could roll back the main thread maps information since the information is available in the thread-specific files" Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com> Cc: Shaohua Li <shli@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc/task_mmu.c')
-rw-r--r--fs/proc/task_mmu.c66
1 files changed, 23 insertions, 43 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4a0c31f904a6..fa95ab2d3674 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -259,23 +259,29 @@ static int do_maps_open(struct inode *inode, struct file *file,
sizeof(struct proc_maps_private));
}
-static pid_t pid_of_stack(struct proc_maps_private *priv,
- struct vm_area_struct *vma, bool is_pid)
+/*
+ * Indicate if the VMA is a stack for the given task; for
+ * /proc/PID/maps that is the stack of the main task.
+ */
+static int is_stack(struct proc_maps_private *priv,
+ struct vm_area_struct *vma, int is_pid)
{
- struct inode *inode = priv->inode;
- struct task_struct *task;
- pid_t ret = 0;
+ int stack = 0;
+
+ if (is_pid) {
+ stack = vma->vm_start <= vma->vm_mm->start_stack &&
+ vma->vm_end >= vma->vm_mm->start_stack;
+ } else {
+ struct inode *inode = priv->inode;
+ struct task_struct *task;
- rcu_read_lock();
- task = pid_task(proc_pid(inode), PIDTYPE_PID);
- if (task) {
- task = task_of_stack(task, vma, is_pid);
+ rcu_read_lock();
+ task = pid_task(proc_pid(inode), PIDTYPE_PID);
if (task)
- ret = task_pid_nr_ns(task, inode->i_sb->s_fs_info);
+ stack = vma_is_stack_for_task(vma, task);
+ rcu_read_unlock();
}
- rcu_read_unlock();
-
- return ret;
+ return stack;
}
static void
@@ -335,8 +341,6 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
name = arch_vma_name(vma);
if (!name) {
- pid_t tid;
-
if (!mm) {
name = "[vdso]";
goto done;
@@ -348,21 +352,8 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
goto done;
}
- tid = pid_of_stack(priv, vma, is_pid);
- if (tid != 0) {
- /*
- * Thread stack in /proc/PID/task/TID/maps or
- * the main process stack.
- */
- if (!is_pid || (vma->vm_start <= mm->start_stack &&
- vma->vm_end >= mm->start_stack)) {
- name = "[stack]";
- } else {
- /* Thread stack in /proc/PID/maps */
- seq_pad(m, ' ');
- seq_printf(m, "[stack:%d]", tid);
- }
- }
+ if (is_stack(priv, vma, is_pid))
+ name = "[stack]";
}
done:
@@ -1618,19 +1609,8 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
seq_file_path(m, file, "\n\t= ");
} else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
seq_puts(m, " heap");
- } else {
- pid_t tid = pid_of_stack(proc_priv, vma, is_pid);
- if (tid != 0) {
- /*
- * Thread stack in /proc/PID/task/TID/maps or
- * the main process stack.
- */
- if (!is_pid || (vma->vm_start <= mm->start_stack &&
- vma->vm_end >= mm->start_stack))
- seq_puts(m, " stack");
- else
- seq_printf(m, " stack:%d", tid);
- }
+ } else if (is_stack(proc_priv, vma, is_pid)) {
+ seq_puts(m, " stack");
}
if (is_vm_hugetlb_page(vma))