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

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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 <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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KOSAKI Motohiro 2010-01-08 14:42:56 -08:00 committed by Linus Torvalds
parent f146aabfe9
commit 1306d603fc
2 changed files with 0 additions and 91 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/filesystems/proc.txt
View File

@ -177,7 +177,6 @@ read the file /proc/PID/status:
CapBnd: ffffffffffffffff CapBnd: ffffffffffffffff
voluntary_ctxt_switches: 0 voluntary_ctxt_switches: 0
nonvoluntary_ctxt_switches: 1 nonvoluntary_ctxt_switches: 1
Stack usage: 12 kB
This shows you nearly the same information you would get if you viewed it with 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 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" Mems_allowed_list Same as previous, but in "list format"
voluntary_ctxt_switches number of voluntary context switches voluntary_ctxt_switches number of voluntary context switches
nonvoluntary_ctxt_switches number of non 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)

89
fs/proc/array.c
View File

@ -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) static void task_cpus_allowed(struct seq_file *m, struct task_struct *task)
{ {
seq_printf(m, "Cpus_allowed:\t"); 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); task_show_regs(m, task);
#endif #endif
task_context_switch_counts(m, task); task_context_switch_counts(m, task);
task_show_stack_usage(m, task);
return 0; return 0;
} }