What does it mean for /proc/kpagecount to be zero
for some entries in /proc/kpagecount, all the 64 bit entry is zeros and yet the page is allocated (confirmed from /proc/kpageflags). What does it mean for kpagecount to be zero for certain physical pages? does that mean that a daemon process is using this memory?
kernel ram proc
asked Nov 13 '14 at 22:16
KeetoKeeto
1084
add a comment |
for some entries in /proc/kpagecount, all the 64 bit entry is zeros and yet the page is allocated (confirmed from /proc/kpageflags). What does it mean for kpagecount to be zero for certain physical pages? does that mean that a daemon process is using this memory?
kernel ram proc
asked Nov 13 '14 at 22:16
KeetoKeeto
1084
add a comment |
for some entries in /proc/kpagecount, all the 64 bit entry is zeros and yet the page is allocated (confirmed from /proc/kpageflags). What does it mean for kpagecount to be zero for certain physical pages? does that mean that a daemon process is using this memory?
kernel ram proc
asked Nov 13 '14 at 22:16
KeetoKeeto
1084
for some entries in /proc/kpagecount, all the 64 bit entry is zeros and yet the page is allocated (confirmed from /proc/kpageflags). What does it mean for kpagecount to be zero for certain physical pages? does that mean that a daemon process is using this memory?
kernel ram proc
kernel ram proc
asked Nov 13 '14 at 22:16
KeetoKeeto
1084
asked Nov 13 '14 at 22:16
KeetoKeeto
1084
asked Nov 13 '14 at 22:16
KeetoKeeto
1084
asked Nov 13 '14 at 22:16
KeetoKeeto
1084
asked Nov 13 '14 at 22:16
KeetoKeeto
1084
1084
add a comment |
add a comment |
1 Answer
1
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proc/kpagecount is a virtual file, when you read it, you get the result of executing function kpagecound_read().
static ssize_t kpagecount_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
// ....
u64 pcount;
pfn = src / KPMSIZE;
count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
if (src & KPMMASK || count & KPMMASK)
return -EINVAL;
while (count > 0) {
if (pfn_valid(pfn))
ppage = pfn_to_page(pfn);
else
ppage = NULL;
if (!ppage || PageSlab(ppage) || page_has_type(ppage))
pcount = 0;
else
pcount = page_mapcount(ppage);
if (put_user(pcount, out)) {
ret = -EFAULT;
break;
}
pfn++;
out++;
count -= KPMSIZE;
cond_resched();
}
// ...
}
and page_has_type() is.
static inline int page_has_type(struct page *page)
{
return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
}
If the entry for a page is zero in kpagecount and is allocated, it means:
- It is used in slabs.
page->page_type < PAGE_MAPCOUNT_RESERVEsee patch :return 0 for special pages that are never mapped. This patch is quite new. Consider when this question is asked, I don't think it's the case.
page_mapcount(page)returns zero. some page are allocated but not mapped.
I'am not sure why. Anyway, you can write kernel module/code that allocate page without create a mapping.
answered Jan 16 at 5:59
reverielreveriel
11
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
proc/kpagecount is a virtual file, when you read it, you get the result of executing function kpagecound_read().
static ssize_t kpagecount_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
// ....
u64 pcount;
pfn = src / KPMSIZE;
count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
if (src & KPMMASK || count & KPMMASK)
return -EINVAL;
while (count > 0) {
if (pfn_valid(pfn))
ppage = pfn_to_page(pfn);
else
ppage = NULL;
if (!ppage || PageSlab(ppage) || page_has_type(ppage))
pcount = 0;
else
pcount = page_mapcount(ppage);
if (put_user(pcount, out)) {
ret = -EFAULT;
break;
}
pfn++;
out++;
count -= KPMSIZE;
cond_resched();
}
// ...
}
and page_has_type() is.
static inline int page_has_type(struct page *page)
{
return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
}
If the entry for a page is zero in kpagecount and is allocated, it means:
- It is used in slabs.
page->page_type < PAGE_MAPCOUNT_RESERVEsee patch :return 0 for special pages that are never mapped. This patch is quite new. Consider when this question is asked, I don't think it's the case.
page_mapcount(page)returns zero. some page are allocated but not mapped.
I'am not sure why. Anyway, you can write kernel module/code that allocate page without create a mapping.
answered Jan 16 at 5:59
reverielreveriel
11
add a comment |
proc/kpagecount is a virtual file, when you read it, you get the result of executing function kpagecound_read().
static ssize_t kpagecount_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
// ....
u64 pcount;
pfn = src / KPMSIZE;
count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
if (src & KPMMASK || count & KPMMASK)
return -EINVAL;
while (count > 0) {
if (pfn_valid(pfn))
ppage = pfn_to_page(pfn);
else
ppage = NULL;
if (!ppage || PageSlab(ppage) || page_has_type(ppage))
pcount = 0;
else
pcount = page_mapcount(ppage);
if (put_user(pcount, out)) {
ret = -EFAULT;
break;
}
pfn++;
out++;
count -= KPMSIZE;
cond_resched();
}
// ...
}
and page_has_type() is.
static inline int page_has_type(struct page *page)
{
return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
}
If the entry for a page is zero in kpagecount and is allocated, it means:
- It is used in slabs.
page->page_type < PAGE_MAPCOUNT_RESERVEsee patch :return 0 for special pages that are never mapped. This patch is quite new. Consider when this question is asked, I don't think it's the case.
page_mapcount(page)returns zero. some page are allocated but not mapped.
I'am not sure why. Anyway, you can write kernel module/code that allocate page without create a mapping.
answered Jan 16 at 5:59
reverielreveriel
11
add a comment |
proc/kpagecount is a virtual file, when you read it, you get the result of executing function kpagecound_read().
static ssize_t kpagecount_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
// ....
u64 pcount;
pfn = src / KPMSIZE;
count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
if (src & KPMMASK || count & KPMMASK)
return -EINVAL;
while (count > 0) {
if (pfn_valid(pfn))
ppage = pfn_to_page(pfn);
else
ppage = NULL;
if (!ppage || PageSlab(ppage) || page_has_type(ppage))
pcount = 0;
else
pcount = page_mapcount(ppage);
if (put_user(pcount, out)) {
ret = -EFAULT;
break;
}
pfn++;
out++;
count -= KPMSIZE;
cond_resched();
}
// ...
}
and page_has_type() is.
static inline int page_has_type(struct page *page)
{
return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
}
If the entry for a page is zero in kpagecount and is allocated, it means:
- It is used in slabs.
page->page_type < PAGE_MAPCOUNT_RESERVEsee patch :return 0 for special pages that are never mapped. This patch is quite new. Consider when this question is asked, I don't think it's the case.
page_mapcount(page)returns zero. some page are allocated but not mapped.
I'am not sure why. Anyway, you can write kernel module/code that allocate page without create a mapping.
answered Jan 16 at 5:59
reverielreveriel
11
proc/kpagecount is a virtual file, when you read it, you get the result of executing function kpagecound_read().
static ssize_t kpagecount_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
// ....
u64 pcount;
pfn = src / KPMSIZE;
count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
if (src & KPMMASK || count & KPMMASK)
return -EINVAL;
while (count > 0) {
if (pfn_valid(pfn))
ppage = pfn_to_page(pfn);
else
ppage = NULL;
if (!ppage || PageSlab(ppage) || page_has_type(ppage))
pcount = 0;
else
pcount = page_mapcount(ppage);
if (put_user(pcount, out)) {
ret = -EFAULT;
break;
}
pfn++;
out++;
count -= KPMSIZE;
cond_resched();
}
// ...
}
and page_has_type() is.
static inline int page_has_type(struct page *page)
{
return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
}
If the entry for a page is zero in kpagecount and is allocated, it means:
- It is used in slabs.
page->page_type < PAGE_MAPCOUNT_RESERVEsee patch :return 0 for special pages that are never mapped. This patch is quite new. Consider when this question is asked, I don't think it's the case.
page_mapcount(page)returns zero. some page are allocated but not mapped.
I'am not sure why. Anyway, you can write kernel module/code that allocate page without create a mapping.
answered Jan 16 at 5:59
reverielreveriel
11
answered Jan 16 at 5:59
reverielreveriel
11
answered Jan 16 at 5:59
reverielreveriel
11
answered Jan 16 at 5:59
reverielreveriel
11
11
add a comment |
add a comment |
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