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authorJohannes Weiner <hannes@cmpxchg.org>2016-02-02 16:57:29 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-02-03 08:28:43 -0800
commit65376df582174ffcec9e6471bf5b0dd79ba05e4a (patch)
tree60c4841a00605605bf8c315783ed48648333e865 /mm/util.c
parent5c2ff95e41c9290d16556cd02e35b25d81be8fe0 (diff)
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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 'mm/util.c')
-rw-r--r--mm/util.c27
1 files changed, 1 insertions, 26 deletions
diff --git a/mm/util.c b/mm/util.c
index c108a6542d05..4fb14ca5a419 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -230,36 +230,11 @@ void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
}
/* Check if the vma is being used as a stack by this task */
-static int vm_is_stack_for_task(struct task_struct *t,
- struct vm_area_struct *vma)
+int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t)
{
return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
}
-/*
- * Check if the vma is being used as a stack.
- * If is_group is non-zero, check in the entire thread group or else
- * just check in the current task. Returns the task_struct of the task
- * that the vma is stack for. Must be called under rcu_read_lock().
- */
-struct task_struct *task_of_stack(struct task_struct *task,
- struct vm_area_struct *vma, bool in_group)
-{
- if (vm_is_stack_for_task(task, vma))
- return task;
-
- if (in_group) {
- struct task_struct *t;
-
- for_each_thread(task, t) {
- if (vm_is_stack_for_task(t, vma))
- return t;
- }
- }
-
- return NULL;
-}
-
#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
void arch_pick_mmap_layout(struct mm_struct *mm)
{