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Message-Id: <20091231231051.1A1B.A69D9226@jp.fujitsu.com>
Date: Thu, 31 Dec 2009 23:12:22 +0900 (JST)
From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: kosaki.motohiro@...fujitsu.com,
Stefani Seibold <stefani@...bold.net>,
Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Alexey Dobriyan <adobriyan@...il.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Randy Dunlap <randy.dunlap@...cle.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] proc: revert to show stack information in /proc/{pid}/status
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.
Cc: Stefani Seibold <stefani@...bold.net>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Alexey Dobriyan <adobriyan@...il.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Randy Dunlap <randy.dunlap@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
Documentation/filesystems/proc.txt | 2 -
fs/proc/array.c | 89 ------------------------------------
2 files changed, 0 insertions(+), 91 deletions(-)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 220cc63..0d07513 100644
--- 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
- 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)
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 2e5c2a3..b8df659 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -322,94 +322,6 @@ 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");
@@ -440,7 +352,6 @@ 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;
}
--
1.6.6
--
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