Hi guys,
Recently, I did a personal kernel hack simply to count how many
anonymous pages that is currently swapped out. Please take a look on
the embedded patch after the end of this message. The patch is made on
top of 2.6.16.1 and tested inside Qemu 0.7.2 using FC2 disk image.
So far, this patch doesn't work as expected. First I check the counter
when nothing swaps out (SwpOut shows zero for all tasks). Then I ran a
memory hogger application (such as "tail -f /dev/zero") to force other
applications to be swapped out partially, then I stopped the mem-hogger
application (since I don't need to fully occupy the RAM anyway). Again,
I checked the counters and some task's counters showed non-zero numbers
(meaning they were swapped out).
The quirk happened here. I disabled the swap areas (swapoff -a) and
AFAIK this would force the kernel to swap-in all the currently swapped
out pages. I re-checked the counters and strangely the swapped counters
didn't go back to zero. What did I do wrong here?
Any suggestions are welcome...
regards,
Mulyadi.
fs/proc/task_mmu.c | 14 ++++++++++++--
include/linux/mm.h | 1 +
mm/memory.c | 2 ++
mm/rmap.c | 1 +
4 files changed, 16 insertions(+), 2 deletions(-)
--- fs/proc/task_mmu.c.bak 2006-03-28 13:49:02.000000000 +0700
+++ fs/proc/task_mmu.c 2006-07-22 19:18:33.000000000 +0700
@@ -15,6 +15,8 @@ char *task_mem(struct mm_struct *mm, cha
{
unsigned long data, text, lib;
unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;
+ struct vm_area_struct * this_vma;
+ unsigned long swp_out_pages=0;
/*
* Note: to minimize their overhead, mm maintains hiwater_vm and
@@ -33,6 +35,12 @@ char *task_mem(struct mm_struct *mm, cha
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;
+
+ for(this_vma = mm->mmap;this_vma;this_vma = this_vma->vm_next)
+ {
+ swp_out_pages += atomic_read(&(this_vma)->swapped_out);
+ }
+
buffer += sprintf(buffer,
"VmPeak:\t%8lu kB\n"
"VmSize:\t%8lu kB\n"
@@ -43,7 +51,8 @@ char *task_mem(struct mm_struct *mm, cha
"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"
+ "VmSwp:\t%8lu kB\n",
hiwater_vm << (PAGE_SHIFT-10),
(total_vm - mm->reserved_vm) << (PAGE_SHIFT-10),
mm->locked_vm << (PAGE_SHIFT-10),
@@ -51,7 +60,8 @@ char *task_mem(struct mm_struct *mm, cha
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,
+ swp_out_pages << (PAGE_SHIFT-10) );
return buffer;
}
--- include/linux/mm.h.bak 2006-03-28 13:49:02.000000000 +0700
+++ include/linux/mm.h 2006-07-22 19:20:34.000000000 +0700
@@ -111,6 +111,7 @@ struct vm_area_struct {
#ifdef CONFIG_NUMA
struct mempolicy *vm_policy; /* NUMA policy for the VMA */
#endif
+ atomic_t swapped_out; /* swapped out pages in this VMA */
};
/*
--- mm/rmap.c.bak 2006-03-28 13:49:02.000000000 +0700
+++ mm/rmap.c 2006-07-22 19:19:47.000000000 +0700
@@ -635,6 +635,7 @@ static int try_to_unmap_one(struct page
set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
BUG_ON(pte_file(*pte));
dec_mm_counter(mm, anon_rss);
+ atomic_inc(&(vma)->swapped_out);
} else
dec_mm_counter(mm, file_rss);
--- mm/memory.c.bak 2006-03-28 13:49:02.000000000 +0700
+++ mm/memory.c 2006-07-22 19:20:10.000000000 +0700
@@ -1928,6 +1928,8 @@ again:
/* The page isn't present yet, go ahead with the fault. */
inc_mm_counter(mm, anon_rss);
+ printk("Reducing swapped_out variable...\n");
+ atomic_dec(&(vma)->swapped_out);
pte = mk_pte(page, vma->vm_page_prot);
if (write_access && can_share_swap_page(page)) {
pte = maybe_mkwrite(pte_mkdirty(pte), vma);
--
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