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From: KAMEZAWA Hiroyuki on 10 Dec 2009 03:10

One of 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(a)bluextal ~]$ cat /proc/self/status
Name: cat
State: R (running)
Tgid: 2904
Pid: 2904
PPid: 2862
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: 504 kB
VmRSS: 504 kB
VmData: 172 kB
VmStk: 84 kB
VmExe: 48 kB
VmLib: 1568 kB
VmPTE: 40 kB
VmSwap: 0 kB <============== this.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com>
---
fs/proc/task_mmu.c | 9 ++++++---
include/linux/mm_types.h | 1 +
mm/memory.c | 16 ++++++++++++----
mm/rmap.c | 3 ++-
mm/swapfile.c | 1 +
5 files changed, 22 insertions(+), 8 deletions(-)

Index: mmotm-2.6.32-Dec8/include/linux/mm_types.h
===================================================================
--- mmotm-2.6.32-Dec8.orig/include/linux/mm_types.h
+++ mmotm-2.6.32-Dec8/include/linux/mm_types.h
@@ -202,6 +202,7 @@ typedef unsigned long mm_counter_t;
enum {
MM_FILEPAGES,
MM_ANONPAGES,
+ MM_SWAPENTS,
NR_MM_COUNTERS
};

Index: mmotm-2.6.32-Dec8/mm/memory.c
===================================================================
--- mmotm-2.6.32-Dec8.orig/mm/memory.c
+++ mmotm-2.6.32-Dec8/mm/memory.c
@@ -650,7 +650,9 @@ copy_one_pte(struct mm_struct *dst_mm, s
&src_mm->mmlist);
spin_unlock(&mmlist_lock);
}
- if (is_write_migration_entry(entry) &&
+ if (likely(!non_swap_entry(entry)))
+ rss[MM_SWAPENTS]++;
+ else if (is_write_migration_entry(entry) &&
is_cow_mapping(vm_flags)) {
/*
* COW mappings require pages in both parent
@@ -945,9 +947,14 @@ static unsigned long zap_pte_range(struc
if (pte_file(ptent)) {
if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
print_bad_pte(vma, addr, ptent, NULL);
- } else if
- (unlikely(!free_swap_and_cache(pte_to_swp_entry(ptent))))
- print_bad_pte(vma, addr, ptent, NULL);
+ } else {
+ swp_entry_t entry = pte_to_swp_entry(ptent);
+
+ if (!non_swap_entry(entry))
+ rss[MM_SWAPENTS]--;
+ if (unlikely(!free_swap_and_cache(entry)))
+ print_bad_pte(vma, addr, ptent, NULL);
+ }
pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
} while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));

@@ -2659,6 +2666,7 @@ static int do_swap_page(struct mm_struct
*/

inc_mm_counter_fast(mm, MM_ANONPAGES);
+ dec_mm_counter_fast(mm, MM_SWAPENTS);
pte = mk_pte(page, vma->vm_page_prot);
if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
pte = maybe_mkwrite(pte_mkdirty(pte), vma);
Index: mmotm-2.6.32-Dec8/mm/rmap.c
===================================================================
--- mmotm-2.6.32-Dec8.orig/mm/rmap.c
+++ mmotm-2.6.32-Dec8/mm/rmap.c
@@ -814,7 +814,7 @@ int try_to_unmap_one(struct page *page,
update_hiwater_rss(mm);

if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
- if (PageAnon(page))
+ if (PageAnon(page)) /* Not increments swapents counter */
dec_mm_counter(mm, MM_ANONPAGES);
else
dec_mm_counter(mm, MM_FILEPAGES);
@@ -840,6 +840,7 @@ int try_to_unmap_one(struct page *page,
spin_unlock(&mmlist_lock);
}
dec_mm_counter(mm, MM_ANONPAGES);
+ inc_mm_counter(mm, MM_SWAPENTS);
} else if (PAGE_MIGRATION) {
/*
* Store the pfn of the page in a special migration
Index: mmotm-2.6.32-Dec8/mm/swapfile.c
===================================================================
--- mmotm-2.6.32-Dec8.orig/mm/swapfile.c
+++ mmotm-2.6.32-Dec8/mm/swapfile.c
@@ -840,6 +840,7 @@ static int unuse_pte(struct vm_area_stru
goto out;
}

+ dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
get_page(page);
set_pte_at(vma->vm_mm, addr, pte,
Index: mmotm-2.6.32-Dec8/fs/proc/task_mmu.c
===================================================================
--- mmotm-2.6.32-Dec8.orig/fs/proc/task_mmu.c
+++ mmotm-2.6.32-Dec8/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
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
"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
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)

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Prev: [RFC mm][PATCH 5/5] counting lowmem rss per mm
Next: [GIT PULL] UBIFS changes for 2.6.33