Commit 1306d603 authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds
Browse files

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: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f146aabf

Documentation/filesystems/proc.txt

+0 −2
Original line number Diff line number Diff line
@@ -177,7 +177,6 @@ read the file /proc/PID/status: 
  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
@@ -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

 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)

fs/proc/array.c

+0 −89
Original line number Diff line number Diff line
@@ -327,94 +327,6 @@ static inline void task_context_switch_counts(struct seq_file *m, 
			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");
@@ -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_stack_usage(m, task);

	return 0;

}

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