mm: count swap usage

A frequent questions from users about memory management is what numbers of
swap ents are user for processes.  And this information will give some
hints to oom-killer.

Besides we can count the number of swapents per a process by scanning
/proc/<pid>/smaps, this is very slow and not good for usual process
information handler which works like 'ps' or 'top'.  (ps or top is now
enough slow..)

This patch adds a counter of swapents to mm_counter and update is at each
swap events.  Information is exported via /proc/<pid>/status file as

[kamezawa@bluextal memory]$ cat /proc/self/status
Name:   cat
State:  R (running)
Tgid:   2910
Pid:    2910
PPid:   2823
TracerPid:      0
Uid:    500     500     500     500
Gid:    500     500     500     500
FDSize: 256
Groups: 500
VmPeak:    82696 kB
VmSize:    82696 kB
VmLck:         0 kB
VmHWM:       432 kB
VmRSS:       432 kB
VmData:      172 kB
VmStk:        84 kB
VmExe:        48 kB
VmLib:      1568 kB
VmPTE:        40 kB
VmSwap:        0 kB <=============== this.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 375581276011..183f8ff5f400 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -16,7 +16,7 @@
 
 void task_mem(struct seq_file *m, struct mm_struct *mm)
 {
-        unsigned long data, text, lib;
+        unsigned long data, text, lib, swap;
         unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;
 
         /*
@@ -36,6 +36,7 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
         data = mm->total_vm - mm->shared_vm - mm->stack_vm;
         text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) >> 10;
         lib = (mm->exec_vm << (PAGE_SHIFT-10)) - text;
+        swap = get_mm_counter(mm, MM_SWAPENTS);
         seq_printf(m,
                 "VmPeak:\t%8lu kB\n"
                 "VmSize:\t%8lu kB\n"
@@ -46,7 +47,8 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
                 "VmStk:\t%8lu kB\n"
                 "VmExe:\t%8lu kB\n"
                 "VmLib:\t%8lu kB\n"
-                "VmPTE:\t%8lu kB\n",
+                "VmPTE:\t%8lu kB\n"
+                "VmSwap:\t%8lu kB\n",
                 hiwater_vm << (PAGE_SHIFT-10),
                 (total_vm - mm->reserved_vm) << (PAGE_SHIFT-10),
                 mm->locked_vm << (PAGE_SHIFT-10),
@@ -54,7 +56,8 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
                 total_rss << (PAGE_SHIFT-10),
                 data << (PAGE_SHIFT-10),
                 mm->stack_vm << (PAGE_SHIFT-10), text, lib,
-                (PTRS_PER_PTE*sizeof(pte_t)*mm->nr_ptes) >> 10);
+                (PTRS_PER_PTE*sizeof(pte_t)*mm->nr_ptes) >> 10,
+                swap << (PAGE_SHIFT-10));
 }
 
 unsigned long task_vsize(struct mm_struct *mm)