proc: partially revert "procfs: provide stack information for threads"

Commit d899bf7b (procfs: provide stack information for threads) introduced
to show stack information in /proc/{pid}/status.  But it cause large
performance regression.  Unfortunately /proc/{pid}/status is used ps
command too and ps is one of most important component.  Because both to
take mmap_sem and page table walk are heavily operation.

If many process run, the ps performance is,

[before d899bf7b]

% perf stat ps >/dev/null

 Performance counter stats for 'ps':

     4090.435806  task-clock-msecs         #      0.032 CPUs
             229  context-switches         #      0.000 M/sec
               0  CPU-migrations           #      0.000 M/sec
             234  page-faults              #      0.000 M/sec
      8587565207  cycles                   #   2099.425 M/sec
      9866662403  instructions             #      1.149 IPC
      3789415411  cache-references         #    926.409 M/sec
        30419509  cache-misses             #      7.437 M/sec

   128.859521955  seconds time elapsed

[after d899bf7b]

% perf stat  ps  > /dev/null

 Performance counter stats for 'ps':

     4305.081146  task-clock-msecs         #      0.028 CPUs
             480  context-switches         #      0.000 M/sec
               2  CPU-migrations           #      0.000 M/sec
             237  page-faults              #      0.000 M/sec
      9021211334  cycles                   #   2095.480 M/sec
     10605887536  instructions             #      1.176 IPC
      3612650999  cache-references         #    839.160 M/sec
        23917502  cache-misses             #      5.556 M/sec

   152.277819582  seconds time elapsed

Thus, this patch revert it. Fortunately /proc/{pid}/task/{tid}/smaps
provide almost same information. we can use it.

Commit d899bf7b introduced two features:

 1) Add the annotattion of [thread stack: xxxx] mark to
    /proc/{pid}/task/{tid}/maps.
 2) Add StackUsage field to /proc/{pid}/status.

I only revert (2), because I haven't seen (1) cause regression.

Signed-off-by: KOSAKI Motohiro <[email protected]>
Cc: Stefani Seibold <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andi Kleen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 220cc6376ef80e0c9bcfec162d45552e729cdf5a..0d07513a67a661440fc1599121bb1dc38560bc33 100644 (file)
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -177,7 +177,6 @@ read the file /proc/PID/status:
   CapBnd: ffffffffffffffff
   voluntary_ctxt_switches:        0
   nonvoluntary_ctxt_switches:     1
   CapBnd: ffffffffffffffff
   voluntary_ctxt_switches:        0
   nonvoluntary_ctxt_switches:     1

-  Stack usage:    12 kB

 
 This shows you nearly the same information you would get if you viewed it with
 the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
 
 This shows you nearly the same information you would get if you viewed it with
 the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its


@@ -231,7 +230,6 @@ Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
  Mems_allowed_list           Same as previous, but in "list format"
  voluntary_ctxt_switches     number of voluntary context switches
  nonvoluntary_ctxt_switches  number of non voluntary context switches
  Mems_allowed_list           Same as previous, but in "list format"
  voluntary_ctxt_switches     number of voluntary context switches
  nonvoluntary_ctxt_switches  number of non voluntary context switches

- Stack usage:                stack usage high water mark (round up to page size)

 ..............................................................................
 
 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
 ..............................................................................
 
 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index f560325c444f0c10e6258ce7c5d9836c58d703b9..13b5d07081751e1cb42aca4ce491c9a52b70ab4f 100644 (file)
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -327,94 +327,6 @@ static inline void task_context_switch_counts(struct seq_file *m,
                        p->nivcsw);
 }
 
                        p->nivcsw);
 }
 

-#ifdef CONFIG_MMU
-
-struct stack_stats {
-       struct vm_area_struct *vma;
-       unsigned long   startpage;
-       unsigned long   usage;
-};
-
-static int stack_usage_pte_range(pmd_t *pmd, unsigned long addr,
-                               unsigned long end, struct mm_walk *walk)
-{
-       struct stack_stats *ss = walk->private;
-       struct vm_area_struct *vma = ss->vma;
-       pte_t *pte, ptent;
-       spinlock_t *ptl;
-       int ret = 0;
-
-       pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
-       for (; addr != end; pte++, addr += PAGE_SIZE) {
-               ptent = *pte;
-
-#ifdef CONFIG_STACK_GROWSUP
-               if (pte_present(ptent) || is_swap_pte(ptent))
-                       ss->usage = addr - ss->startpage + PAGE_SIZE;
-#else
-               if (pte_present(ptent) || is_swap_pte(ptent)) {
-                       ss->usage = ss->startpage - addr + PAGE_SIZE;
-                       pte++;
-                       ret = 1;
-                       break;
-               }
-#endif
-       }
-       pte_unmap_unlock(pte - 1, ptl);
-       cond_resched();
-       return ret;
-}
-
-static inline unsigned long get_stack_usage_in_bytes(struct vm_area_struct *vma,
-                               struct task_struct *task)
-{
-       struct stack_stats ss;
-       struct mm_walk stack_walk = {
-               .pmd_entry = stack_usage_pte_range,
-               .mm = vma->vm_mm,
-               .private = &ss,
-       };
-
-       if (!vma->vm_mm || is_vm_hugetlb_page(vma))
-               return 0;
-
-       ss.vma = vma;
-       ss.startpage = task->stack_start & PAGE_MASK;
-       ss.usage = 0;
-
-#ifdef CONFIG_STACK_GROWSUP
-       walk_page_range(KSTK_ESP(task) & PAGE_MASK, vma->vm_end,
-               &stack_walk);
-#else
-       walk_page_range(vma->vm_start, (KSTK_ESP(task) & PAGE_MASK) + PAGE_SIZE,
-               &stack_walk);
-#endif
-       return ss.usage;
-}
-
-static inline void task_show_stack_usage(struct seq_file *m,
-                                               struct task_struct *task)
-{
-       struct vm_area_struct   *vma;
-       struct mm_struct        *mm = get_task_mm(task);
-
-       if (mm) {
-               down_read(&mm->mmap_sem);
-               vma = find_vma(mm, task->stack_start);
-               if (vma)
-                       seq_printf(m, "Stack usage:\t%lu kB\n",
-                               get_stack_usage_in_bytes(vma, task) >> 10);
-
-               up_read(&mm->mmap_sem);
-               mmput(mm);
-       }
-}
-#else
-static void task_show_stack_usage(struct seq_file *m, struct task_struct *task)
-{
-}
-#endif         /* CONFIG_MMU */
-

 static void task_cpus_allowed(struct seq_file *m, struct task_struct *task)
 {
        seq_printf(m, "Cpus_allowed:\t");
 static void task_cpus_allowed(struct seq_file *m, struct task_struct *task)
 {
        seq_printf(m, "Cpus_allowed:\t");


@@ -445,7 +357,6 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
        task_show_regs(m, task);
 #endif
        task_context_switch_counts(m, task);
        task_show_regs(m, task);
 #endif
        task_context_switch_counts(m, task);

-       task_show_stack_usage(m, task);

        return 0;
 }
 
        return 0;
 }