Commit 1306d603 authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds
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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
......@@ -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)
......
......@@ -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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