Re: [Bug 53501] New: Duplicated MemTotal with different values

Re: [Bug 53501] New: Duplicated MemTotal with different values

[Andrew Morton]

(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Fri,  8 Feb 2013 09:39:27 +0000 (UTC)
bugzilla-daemon@bugzilla.kernel.org wrote:

> https://bugzilla.kernel.org/show_bug.cgi?id=53501
> 
>            Summary: Duplicated MemTotal with different values
>            Product: Memory Management
>            Version: 2.5
>     Kernel Version: Ubuntu 3.8.0-4.8-generic 3.8.0-rc6
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>         AssignedTo: akpm@linux-foundation.org
>         ReportedBy: sworddragon2@aol.com
>         Regression: No
> 
> 
> The installed memory on my system is 16 GiB. /proc/meminfo is showing me
> "MemTotal:       16435048 kB" but /sys/devices/system/node/node0/meminfo is
> showing me "Node 0 MemTotal:       16776380 kB".
> 
> My suggestion: MemTotal in /proc/meminfo should be 16776380 kB too. The old
> value of 16435048 kB could have its own key "MemAvailable".

hm, mine does that too.  A discrepancy between `totalram_pages' and
NODE_DATA(0)->node_present_pages.

I don't know what the reasons are for that but yes, one would expect
the per-node MemTotals to sum up to the global one.

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[David Rientjes]

On Tue, 12 Feb 2013, Andrew Morton wrote:

> >            Summary: Duplicated MemTotal with different values
> >            Product: Memory Management
> >            Version: 2.5
> >     Kernel Version: Ubuntu 3.8.0-4.8-generic 3.8.0-rc6
> >           Platform: All
> >         OS/Version: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: normal
> >           Priority: P1
> >          Component: Other
> >         AssignedTo: akpm@linux-foundation.org
> >         ReportedBy: sworddragon2@aol.com
> >         Regression: No
> > 
> > 
> > The installed memory on my system is 16 GiB. /proc/meminfo is showing me
> > "MemTotal:       16435048 kB" but /sys/devices/system/node/node0/meminfo is
> > showing me "Node 0 MemTotal:       16776380 kB".
> > 
> > My suggestion: MemTotal in /proc/meminfo should be 16776380 kB too. The old
> > value of 16435048 kB could have its own key "MemAvailable".
> 
> hm, mine does that too.  A discrepancy between `totalram_pages' and
> NODE_DATA(0)->node_present_pages.
> 
> I don't know what the reasons are for that but yes, one would expect
> the per-node MemTotals to sum up to the global one.
> 

I'd suspect it has something to do with 9feedc9d831e ("mm: introduce new 
field "managed_pages" to struct zone") and 3.8 would be the first kernel 
release with this change.  Is it possible to try 3.7 or, better yet, with 
this patch reverted?

If neither of these are the case, or you aren't comfortable building and 
booting a custom kernel, please send along your /proc/zoneinfo.

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[Andrew Morton]

On Tue, 12 Feb 2013 17:45:42 -0800 (PST) David Rientjes <rientjes@google.com> wrote:

> > > The installed memory on my system is 16 GiB. /proc/meminfo is showing me
> > > "MemTotal:       16435048 kB" but /sys/devices/system/node/node0/meminfo is
> > > showing me "Node 0 MemTotal:       16776380 kB".
> > > 
> > > My suggestion: MemTotal in /proc/meminfo should be 16776380 kB too. The old
> > > value of 16435048 kB could have its own key "MemAvailable".
> > 
> > hm, mine does that too.  A discrepancy between `totalram_pages' and
> > NODE_DATA(0)->node_present_pages.
> > 
> > I don't know what the reasons are for that but yes, one would expect
> > the per-node MemTotals to sum up to the global one.
> > 
> 
> I'd suspect it has something to do with 9feedc9d831e ("mm: introduce new 
> field "managed_pages" to struct zone") and 3.8 would be the first kernel 
> release with this change.  Is it possible to try 3.7 or, better yet, with 
> this patch reverted?

My desktop machine at google in inconsistent, as is the 2.6.32-based
machine, so it obviously predates 9feedc9d831e.

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[David Rientjes]

On Tue, 12 Feb 2013, Andrew Morton wrote:

> > > > The installed memory on my system is 16 GiB. /proc/meminfo is showing me
> > > > "MemTotal:       16435048 kB" but /sys/devices/system/node/node0/meminfo is
> > > > showing me "Node 0 MemTotal:       16776380 kB".
> > > > 
> > > > My suggestion: MemTotal in /proc/meminfo should be 16776380 kB too. The old
> > > > value of 16435048 kB could have its own key "MemAvailable".
> > > 
> > > hm, mine does that too.  A discrepancy between `totalram_pages' and
> > > NODE_DATA(0)->node_present_pages.
> > > 
> > > I don't know what the reasons are for that but yes, one would expect
> > > the per-node MemTotals to sum up to the global one.
> > > 
> > 
> > I'd suspect it has something to do with 9feedc9d831e ("mm: introduce new 
> > field "managed_pages" to struct zone") and 3.8 would be the first kernel 
> > release with this change.  Is it possible to try 3.7 or, better yet, with 
> > this patch reverted?
> 
> My desktop machine at google in inconsistent, as is the 2.6.32-based
> machine, so it obviously predates 9feedc9d831e.
> 

Hmm, ok.  The question is which one is right: the per-node MemTotal is the 
amount of present RAM, the spanned range minus holes, and the system 
MemTotal is the amount of pages released to the buddy allocator by 
bootmem and discounts not only the memory holes but also reserved pages.  
Should they both be the amount of RAM present or the amount of unreserved 
RAM present?

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[Jiang Liu]

On 02/14/2013 11:19 AM, David Rientjes wrote:
> On Tue, 12 Feb 2013, Andrew Morton wrote:
> 
>>>>> The installed memory on my system is 16 GiB. /proc/meminfo is showing me
>>>>> "MemTotal:       16435048 kB" but /sys/devices/system/node/node0/meminfo is
>>>>> showing me "Node 0 MemTotal:       16776380 kB".
>>>>>
>>>>> My suggestion: MemTotal in /proc/meminfo should be 16776380 kB too. The old
>>>>> value of 16435048 kB could have its own key "MemAvailable".
>>>>
>>>> hm, mine does that too.  A discrepancy between `totalram_pages' and
>>>> NODE_DATA(0)->node_present_pages.
>>>>
>>>> I don't know what the reasons are for that but yes, one would expect
>>>> the per-node MemTotals to sum up to the global one.
>>>>
>>>
>>> I'd suspect it has something to do with 9feedc9d831e ("mm: introduce new 
>>> field "managed_pages" to struct zone") and 3.8 would be the first kernel 
>>> release with this change.  Is it possible to try 3.7 or, better yet, with 
>>> this patch reverted?
>>
>> My desktop machine at google in inconsistent, as is the 2.6.32-based
>> machine, so it obviously predates 9feedc9d831e.
>>
> 
> Hmm, ok.  The question is which one is right: the per-node MemTotal is the 
> amount of present RAM, the spanned range minus holes, and the system 
> MemTotal is the amount of pages released to the buddy allocator by 
> bootmem and discounts not only the memory holes but also reserved pages.  
> Should they both be the amount of RAM present or the amount of unreserved 
> RAM present?
> 
Hi David,
	We have worked out a patch set to address this issue. The first two
patches have been merged into v3.8, and another two patches are queued in
Andrew's mm tree for v3.9.
	The patch set introduces a new field named managed_pages into struct
zone to distinguish between pages present in a zone and pages managed by the
buddy system. So
zone->present_pages = zone->spanned_pages - pages_in_hole;
zone->managed_pages = pages_managed_by_buddy_system_in_the_zone;
	We have also added a field named "managed" into /proc/zoneinfo, but
haven't touch /proc/meminfo and /sys/devices/system/node/nodex/meminfo yet.
If preferred, we could work out another patch to enhance these two files
as suggested above.
	Regards!
	Gerry
 

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[David Rientjes]

On Thu, 14 Feb 2013, Jiang Liu wrote:

> > Hmm, ok.  The question is which one is right: the per-node MemTotal is the 
> > amount of present RAM, the spanned range minus holes, and the system 
> > MemTotal is the amount of pages released to the buddy allocator by 
> > bootmem and discounts not only the memory holes but also reserved pages.  
> > Should they both be the amount of RAM present or the amount of unreserved 
> > RAM present?
> > 
> Hi David,
> 	We have worked out a patch set to address this issue. The first two
> patches have been merged into v3.8, and another two patches are queued in
> Andrew's mm tree for v3.9.
> 	The patch set introduces a new field named managed_pages into struct
> zone to distinguish between pages present in a zone and pages managed by the
> buddy system. So
> zone->present_pages = zone->spanned_pages - pages_in_hole;
> zone->managed_pages = pages_managed_by_buddy_system_in_the_zone;
> 	We have also added a field named "managed" into /proc/zoneinfo, but
> haven't touch /proc/meminfo and /sys/devices/system/node/nodex/meminfo yet.
> If preferred, we could work out another patch to enhance these two files
> as suggested above.

I'm glad this is a known issue that you're working on, but my question 
still stands: if MemTotal is going to be consistent throughout 
/proc/meminfo and /sys/devices/system/node/nodeX/meminfo, which is 
correct?  The present RAM minus holes or the amount available to the buddy 
allocator not including reserved memory?

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[PATCH 1/2] vm: add 'MemManaged' field to /proc/meminfo and /sys/.../nodex/meminfo

[Jiang Liu]

As reported by https://bugzilla.kernel.org/show_bug.cgi?id=53501,
"MemTotal" from /proc/meminfo means memory pages managed by the buddy
system (managed_pages), but "MemTotal" from /sys/.../node/nodex/meminfo
means phsical pages present (present_pages) within the NUMA node.
There's a difference between managed_pages and present_pages due to
bootmem allocator and reserved pages.

So introduce a new field "MemManaged" to /sys/.../nodex/meminfo and
/proc/meminfo, so that:
MemTotal = present_pages
MemManaged = managed_pages = present_pages - reserved_pages

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Reported-by: sworddragon2@aol.com
---
Hi Andrew and David,
	How about these draft patches? It just passes compilation. If you
are OK with them, we will conduct tests tomorrow.
	Regards!
	Gerry
---
 drivers/base/node.c |    2 ++
 fs/proc/meminfo.c   |    2 ++
 mm/page_alloc.c     |   19 ++++++++++++++++++-
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index fac124a..6508c4d 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -66,6 +66,7 @@ static ssize_t node_read_meminfo(struct device *dev,
 	si_meminfo_node(&i, nid);
 	n = sprintf(buf,
 		       "Node %d MemTotal:       %8lu kB\n"
+		       "Node %d MemManaged:     %8lu kB\n"
 		       "Node %d MemFree:        %8lu kB\n"
 		       "Node %d MemUsed:        %8lu kB\n"
 		       "Node %d Active:         %8lu kB\n"
@@ -77,6 +78,7 @@ static ssize_t node_read_meminfo(struct device *dev,
 		       "Node %d Unevictable:    %8lu kB\n"
 		       "Node %d Mlocked:        %8lu kB\n",
 		       nid, K(i.totalram),
+		       nid, K(i.sharedram),
 		       nid, K(i.freeram),
 		       nid, K(i.totalram - i.freeram),
 		       nid, K(node_page_state(nid, NR_ACTIVE_ANON) +
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 80e4645..5d58cbb 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -54,6 +54,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	 */
 	seq_printf(m,
 		"MemTotal:       %8lu kB\n"
+		"MemManaged:     %8lu kB\n"
 		"MemFree:        %8lu kB\n"
 		"Buffers:        %8lu kB\n"
 		"Cached:         %8lu kB\n"
@@ -106,6 +107,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 #endif
 		,
 		K(i.totalram),
+		K(totalram_pages),
 		K(i.freeram),
 		K(i.bufferram),
 		K(cached),
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 595e655..6884dc5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2830,7 +2830,13 @@ static inline void show_node(struct zone *zone)
 
 void si_meminfo(struct sysinfo *val)
 {
-	val->totalram = totalram_pages;
+	int nid;
+	unsigned long present_pages = 0;
+
+	for_each_node_state(nid, N_MEMORY)
+		present_pages += node_present_pages(nid);
+
+	val->totalram = present_pages;
 	val->sharedram = 0;
 	val->freeram = global_page_state(NR_FREE_PAGES);
 	val->bufferram = nr_blockdev_pages();
@@ -2844,8 +2850,19 @@ EXPORT_SYMBOL(si_meminfo);
 #ifdef CONFIG_NUMA
 void si_meminfo_node(struct sysinfo *val, int nid)
 {
+	int zone_type;
+	unsigned long managed_pages = 0;
 	pg_data_t *pgdat = NODE_DATA(nid);
 
+	for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++)
+		managed_pages += pgdat->node_zones[zone_type].managed_pages;
+
+	/*
+	 * Ugly hack: struct sysinfo is exported to userspace and there's no
+	 * space available for a new field "managedram", so reuse field
+	 * "sharedram".
+	 */
+	val->sharedram = managed_pages;
 	val->totalram = pgdat->node_present_pages;
 	val->freeram = node_page_state(nid, NR_FREE_PAGES);
 #ifdef CONFIG_HIGHMEM
-- 
1.7.9.5

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[PATCH 2/2] mm: protect si_meminfo() and si_meminfo_node() from memory hotplug operations

[Jiang Liu]

There's typical usage of si_meminfo as below:
	si_meminfo(&si);
	threshold = si->totalram - si.totalhigh;

It may cause underflow if memory hotplug races with si_meminfo() because
there's no mechanism to protect si_meminfo() from memory hotplug
operations. And some callers expects that si_meminfo() is a lightweight
operations. So introduce a lightweight mechanism to protect si_meminfo()
from memory hotplug operations.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
---
 mm/page_alloc.c |   24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6884dc5..5cf03d4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2831,18 +2831,34 @@ static inline void show_node(struct zone *zone)
 void si_meminfo(struct sysinfo *val)
 {
 	int nid;
-	unsigned long present_pages = 0;
+	unsigned long present_pages;
 
+	val->sharedram = 0;
+	val->mem_unit = PAGE_SIZE;
+
+restart:
+	present_pages = 0;
 	for_each_node_state(nid, N_MEMORY)
 		present_pages += node_present_pages(nid);
 
 	val->totalram = present_pages;
-	val->sharedram = 0;
 	val->freeram = global_page_state(NR_FREE_PAGES);
 	val->bufferram = nr_blockdev_pages();
 	val->totalhigh = totalhigh_pages;
 	val->freehigh = nr_free_highpages();
-	val->mem_unit = PAGE_SIZE;
+
+	/*
+	 * si_meminfo() may generate invalid results because it isn't protected
+	 * from memory hotplug operaitons. And some callers expect that it's an
+	 * lightweigh operation. So provide minimal protections without heavy
+	 * overhead.
+	 */
+	if (val->totalram < val->freeram ||
+	    val->totalram < val->bufferram ||
+	    val->totalram < val->totalhigh ||
+	    val->totalhigh < val->freehigh ||
+	    val->freeram < val->freehigh)
+		goto restart;
 }
 
 EXPORT_SYMBOL(si_meminfo);
@@ -2854,6 +2870,7 @@ void si_meminfo_node(struct sysinfo *val, int nid)
 	unsigned long managed_pages = 0;
 	pg_data_t *pgdat = NODE_DATA(nid);
 
+	lock_memory_hotplug();
 	for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++)
 		managed_pages += pgdat->node_zones[zone_type].managed_pages;
 
@@ -2874,6 +2891,7 @@ void si_meminfo_node(struct sysinfo *val, int nid)
 	val->freehigh = 0;
 #endif
 	val->mem_unit = PAGE_SIZE;
+	unlock_memory_hotplug();
 }
 #endif
 
-- 
1.7.9.5

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Re: [PATCH 1/2] vm: add 'MemManaged' field to /proc/meminfo and /sys/.../nodex/meminfo

[David Rientjes]

On Sun, 17 Feb 2013, Jiang Liu wrote:

> As reported by https://bugzilla.kernel.org/show_bug.cgi?id=53501,
> "MemTotal" from /proc/meminfo means memory pages managed by the buddy
> system (managed_pages), but "MemTotal" from /sys/.../node/nodex/meminfo
> means phsical pages present (present_pages) within the NUMA node.
> There's a difference between managed_pages and present_pages due to
> bootmem allocator and reserved pages.
> 
> So introduce a new field "MemManaged" to /sys/.../nodex/meminfo and
> /proc/meminfo, so that:
> MemTotal = present_pages
> MemManaged = managed_pages = present_pages - reserved_pages
> 

Nobody is asking for a MemManaged field, we're asking for consistency in 
MemTotal as exported by /proc/meminfo and 
/sys/devices/system/node/node*/meminfo.  In my opinion, this should be the 
amount of RAM installed on the system regardless of the amount of memory 
reserved, i.e. the current /sys/devices/system/node/node*/meminfo 
semantics.  There is no implicit guarantee that memory in MemTotal can be 
allocated by the buddy allocator.

So how about we just make the MemTotal in /proc/meminfo coincide with 
these semantics?

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Re: [PATCH 2/2] mm: protect si_meminfo() and si_meminfo_node() from memory hotplug operations

[David Rientjes]

On Sun, 17 Feb 2013, Jiang Liu wrote:

> There's typical usage of si_meminfo as below:
> 	si_meminfo(&si);
> 	threshold = si->totalram - si.totalhigh;
> 
> It may cause underflow if memory hotplug races with si_meminfo() because
> there's no mechanism to protect si_meminfo() from memory hotplug
> operations. And some callers expects that si_meminfo() is a lightweight
> operations. So introduce a lightweight mechanism to protect si_meminfo()
> from memory hotplug operations.
> 

Instead of this, I think it would be appropriate to add a comment that 
requires synchronization if two fields are going to be compared, i.e. use 
{lock,unlock}_memory_hotplug() in the caller to si_meminfo(), or 
appropriate underflow checking is done upon return.

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[Simon Jeons]

Hi David,
On 02/15/2013 08:26 AM, David Rientjes wrote:
> On Thu, 14 Feb 2013, Jiang Liu wrote:
>
>>> Hmm, ok.  The question is which one is right: the per-node MemTotal is the
>>> amount of present RAM, the spanned range minus holes, and the system
>>> MemTotal is the amount of pages released to the buddy allocator by
>>> bootmem and discounts not only the memory holes but also reserved pages.
>>> Should they both be the amount of RAM present or the amount of unreserved
>>> RAM present?
>>>
>> Hi David,
>> 	We have worked out a patch set to address this issue. The first two
>> patches have been merged into v3.8, and another two patches are queued in
>> Andrew's mm tree for v3.9.
>> 	The patch set introduces a new field named managed_pages into struct
>> zone to distinguish between pages present in a zone and pages managed by the
>> buddy system. So
>> zone->present_pages = zone->spanned_pages - pages_in_hole;
>> zone->managed_pages = pages_managed_by_buddy_system_in_the_zone;
>> 	We have also added a field named "managed" into /proc/zoneinfo, but
>> haven't touch /proc/meminfo and /sys/devices/system/node/nodex/meminfo yet.
>> If preferred, we could work out another patch to enhance these two files
>> as suggested above.
> I'm glad this is a known issue that you're working on, but my question
> still stands: if MemTotal is going to be consistent throughout
> /proc/meminfo and /sys/devices/system/node/nodeX/meminfo, which is
> correct?  The present RAM minus holes or the amount available to the buddy
> allocator not including reserved memory?

What I confuse is why have /proc/meminfo and /proc/vmstat at the same 
time, they both use to monitor memory subsystem states. What's the root 
reason?

>
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Re: [Bug 53501] New: Duplicated MemTotal with different values

[David Rientjes]

On Wed, 20 Feb 2013, Simon Jeons wrote:

> What I confuse is why have /proc/meminfo and /proc/vmstat at the same time,
> they both use to monitor memory subsystem states. What's the root reason?
> 

This has nothing to do with this thread, but /proc/vmstat actually does 
not include the MemTotal value being discussed in this thread that 
/proc/meminfo does.  /proc/meminfo is typically the interface used by 
applications, probably mostly for historical purposes since both are 
present when procfs is configured and mounted, but also to avoid 
determining the native page size.  There's no implicit userspace API 
exported by /proc/vmstat.

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[PATCH v2] mm: let /proc/meminfo report physical memory installed as "MemTotal"

[Jiang Liu]

As reported by https://bugzilla.kernel.org/show_bug.cgi?id=53501,
"MemTotal" from /proc/meminfo means memory pages managed by the buddy
system (managed_pages), but "MemTotal" from /sys/.../node/nodex/meminfo
means phsical pages present (present_pages) within the NUMA node.
There's a difference between managed_pages and present_pages due to
bootmem allocator and reserved pages.

So change /proc/meminfo to report physical memory installed as
"MemTotal", which is
MemTotal = sum(pgdat->present_pages)

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Reported-by: sworddragon2@aol.com
---
Hi David,
	How about this simpilified version?
	Regards!
	Gerry
---
 mm/page_alloc.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e4e8bf1..8e53d6e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2835,7 +2835,13 @@ static inline void show_node(struct zone *zone)
 
 void si_meminfo(struct sysinfo *val)
 {
-	val->totalram = totalram_pages;
+	int nid;
+	unsigned long present_pages = 0;
+
+	for_each_node_state(nid, N_MEMORY)
+		present_pages += node_present_pages(nid);
+
+	val->totalram = present_pages;
 	val->sharedram = 0;
 	val->freeram = global_page_state(NR_FREE_PAGES);
 	val->bufferram = nr_blockdev_pages();
-- 
1.7.9.5

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Re: [PATCH v2] mm: let /proc/meminfo report physical memory installed as "MemTotal"

[Andrew Morton]

On Thu, 21 Feb 2013 01:27:25 +0800
Jiang Liu <liuj97@gmail.com> wrote:

> As reported by https://bugzilla.kernel.org/show_bug.cgi?id=53501,
> "MemTotal" from /proc/meminfo means memory pages managed by the buddy
> system (managed_pages), but "MemTotal" from /sys/.../node/nodex/meminfo
> means phsical pages present (present_pages) within the NUMA node.
> There's a difference between managed_pages and present_pages due to
> bootmem allocator and reserved pages.
> 
> So change /proc/meminfo to report physical memory installed as
> "MemTotal", which is
> MemTotal = sum(pgdat->present_pages)

Documentation/filesystems/proc.txt says

    MemTotal: Total usable ram (i.e. physical ram minus a few reserved
              bits and the kernel binary code)

And arguably, that is more useful than "total physical memory".

Presumably the per-node MemTotals are including kernel memory and
reserved memory.  Maybe they should be fixed instead (sounds hard).

Or maybe we just leave everything as-is and document it carefully.

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Re: [PATCH v2] mm: let /proc/meminfo report physical memory installed as "MemTotal"

[Jiang Liu]

On 02/21/2013 06:49 AM, Andrew Morton wrote:
> On Thu, 21 Feb 2013 01:27:25 +0800
> Jiang Liu <liuj97@gmail.com> wrote:
> 
>> As reported by https://bugzilla.kernel.org/show_bug.cgi?id=53501,
>> "MemTotal" from /proc/meminfo means memory pages managed by the buddy
>> system (managed_pages), but "MemTotal" from /sys/.../node/nodex/meminfo
>> means phsical pages present (present_pages) within the NUMA node.
>> There's a difference between managed_pages and present_pages due to
>> bootmem allocator and reserved pages.
>>
>> So change /proc/meminfo to report physical memory installed as
>> "MemTotal", which is
>> MemTotal = sum(pgdat->present_pages)
> 
> Documentation/filesystems/proc.txt says
> 
>     MemTotal: Total usable ram (i.e. physical ram minus a few reserved
>               bits and the kernel binary code)
> 
> And arguably, that is more useful than "total physical memory".
> 
> Presumably the per-node MemTotals are including kernel memory and
> reserved memory.  Maybe they should be fixed instead (sounds hard).
Hi Andrew,
	It's really hard, but I think it deserve it because have reduced
about 460 lines of code when fixing this bug. So how about following
patchset?
	The first 27 patches introduces some help functions to simplify
free_initmem() and free_initrd_mem() for most arches.
	The 28th patch increases zone->managed_pages when freeing reserved
pages.
	The 29th patch change /sys/.../nodex/meminfo to report "available
pages within the node" as MemTatoal.
	Regards!
	Gerry

Jiang Liu (29):
  mm: introduce free_reserved_mem/page() to reduce duplicated code
  mm/alpha: use common help functions to free reserved pages
  mm/ARM: use common help functions to free reserved pages
  mm/avr32: use common help functions to free reserved pages
  mm/blackfin: use common help functions to free reserved pages
  mm/c6x: use common help functions to free reserved pages
  mm/cris: use common help functions to free reserved pages
  mm/FRV: use common help functions to free reserved pages
  mm/h8300: use common help functions to free reserved pages
  mm/IA64: use common help functions to free reserved pages
  mm/m32r: use common help functions to free reserved pages
  mm/m68k: use common help functions to free reserved pages
  mm/microblaze: use common help functions to free reserved pages
  mm/MIPS: use common help functions to free reserved pages
  mm/mn10300: use common help functions to free reserved pages
  mm/openrisc: use common help functions to free reserved pages
  mm/parisc: use common help functions to free reserved pages
  mm/ppc: use common help functions to free reserved pages
  mm/s390: use common help functions to free reserved pages
  mm/score: use common help functions to free reserved pages
  mm/SH: use common help functions to free reserved pages
  mm/SPARC: use common help functions to free reserved pages
  mm/um: use common help functions to free reserved pages
  mm/unicore32: use common help functions to free reserved pages
  mm/x86: use common help functions to free reserved pages
  mm/xtensa: use common help functions to free reserved pages
  mm,kexec: use common help functions to free reserved pages
  mm: increase zone->managed_pages when freeing reserved pages
  mm: report available pages as "MemTotal" for each NUMA node

 arch/alpha/kernel/sys_nautilus.c             |    5 ++-
 arch/alpha/mm/init.c                         |   21 ++----------
 arch/arm/mm/init.c                           |   43 ++++++++++--------------
 arch/arm64/mm/init.c                         |   26 ++-------------
 arch/avr32/mm/init.c                         |   24 ++------------
 arch/blackfin/mm/init.c                      |   20 ++----------
 arch/c6x/mm/init.c                           |   30 ++---------------
 arch/cris/mm/init.c                          |   12 +------
 arch/frv/mm/init.c                           |   26 ++-------------
 arch/h8300/mm/init.c                         |   28 ++--------------
 arch/ia64/mm/init.c                          |   23 +++----------
 arch/m32r/mm/init.c                          |   21 ++----------
 arch/m68k/mm/init.c                          |   24 ++------------
 arch/microblaze/include/asm/setup.h          |    1 -
 arch/microblaze/mm/init.c                    |   28 ++--------------
 arch/mips/mm/init.c                          |   13 ++------
 arch/mn10300/mm/init.c                       |   23 ++-----------
 arch/openrisc/mm/init.c                      |   23 ++-----------
 arch/parisc/mm/init.c                        |   23 ++-----------
 arch/powerpc/kernel/crash_dump.c             |    5 +--
 arch/powerpc/kernel/fadump.c                 |    5 +--
 arch/powerpc/kernel/kvm.c                    |    7 +---
 arch/powerpc/mm/mem.c                        |   29 ++---------------
 arch/powerpc/platforms/512x/mpc512x_shared.c |    5 +--
 arch/s390/mm/init.c                          |   23 ++-----------
 arch/score/mm/init.c                         |   25 ++------------
 arch/sh/mm/init.c                            |   22 ++-----------
 arch/sparc/kernel/leon_smp.c                 |   15 ++-------
 arch/sparc/mm/init_32.c                      |   40 ++++-------------------
 arch/sparc/mm/init_64.c                      |   20 ++----------
 arch/tile/mm/init.c                          |    1 +
 arch/um/kernel/mem.c                         |   10 +-----
 arch/unicore32/mm/init.c                     |   26 ++-------------
 arch/x86/mm/init.c                           |    5 +--
 arch/xtensa/mm/init.c                        |   21 ++----------
 include/linux/mm.h                           |   45 ++++++++++++++++++++++++++
 kernel/kexec.c                               |    8 ++---
 mm/page_alloc.c                              |    8 ++++-
 38 files changed, 139 insertions(+), 595 deletions(-)


> 
> Or maybe we just leave everything as-is and document it carefully.
> 

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Re: [PATCH v2] mm: let /proc/meminfo report physical memory installed as "MemTotal"

[Andrew Morton]

On Fri, 22 Feb 2013 01:26:02 +0800
Jiang Liu <liuj97@gmail.com> wrote:

> 	It's really hard, but I think it deserve it because have reduced
> about 460 lines of code when fixing this bug. So how about following
> patchset?
> 	The first 27 patches introduces some help functions to simplify
> free_initmem() and free_initrd_mem() for most arches.
> 	The 28th patch increases zone->managed_pages when freeing reserved
> pages.
> 	The 29th patch change /sys/.../nodex/meminfo to report "available
> pages within the node" as MemTatoal.

yikes.

Let's defer the problem for now.  Please send the patches out in the
usual fashion after 3.9-rc1 and we'll take a look?

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Re: [PATCH v2] mm: let /proc/meminfo report physical memory installed as "MemTotal"

[Jiang Liu]

On 02/22/2013 05:31 AM, Andrew Morton wrote:
> On Fri, 22 Feb 2013 01:26:02 +0800
> Jiang Liu <liuj97@gmail.com> wrote:
> 
>> 	It's really hard, but I think it deserve it because have reduced
>> about 460 lines of code when fixing this bug. So how about following
>> patchset?
>> 	The first 27 patches introduces some help functions to simplify
>> free_initmem() and free_initrd_mem() for most arches.
>> 	The 28th patch increases zone->managed_pages when freeing reserved
>> pages.
>> 	The 29th patch change /sys/.../nodex/meminfo to report "available
>> pages within the node" as MemTatoal.
> 
> yikes.
> 
> Let's defer the problem for now.  Please send the patches out in the
> usual fashion after 3.9-rc1 and we'll take a look?
> 
Sure, will send out those patches after 3.9-rc1 is out.

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[Simon Jeons]

On 02/20/2013 03:09 PM, David Rientjes wrote:
> On Wed, 20 Feb 2013, Simon Jeons wrote:
>
>> What I confuse is why have /proc/meminfo and /proc/vmstat at the same time,
>> they both use to monitor memory subsystem states. What's the root reason?
>>
> This has nothing to do with this thread, but /proc/vmstat actually does
> not include the MemTotal value being discussed in this thread that
> /proc/meminfo does.  /proc/meminfo is typically the interface used by
> applications, probably mostly for historical purposes since both are

Do you mean /proc/vmstat is not used by  applications.
sar -B 1
pgpgin/s pgpgout/s   fault/s  majflt/s  pgfree/s pgscank/s pgscand/s 
pgsteal/s %vmeff
I think they are read from /proc/vmstat

> present when procfs is configured and mounted, but also to avoid
> determining the native page size.  There's no implicit userspace API
> exported by /proc/vmstat.

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[David Rientjes]

On Sat, 2 Mar 2013, Simon Jeons wrote:

> > This has nothing to do with this thread, but /proc/vmstat actually does
> > not include the MemTotal value being discussed in this thread that
> > /proc/meminfo does.  /proc/meminfo is typically the interface used by
> > applications, probably mostly for historical purposes since both are
> 
> Do you mean /proc/vmstat is not used by  applications.
> sar -B 1
> pgpgin/s pgpgout/s   fault/s  majflt/s  pgfree/s pgscank/s pgscand/s pgsteal/s
> %vmeff
> I think they are read from /proc/vmstat
> 

Yes, there is userspace code that parses /proc/vmstat.

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[Simon Jeons]

On 03/04/2013 07:18 PM, David Rientjes wrote:
> On Sat, 2 Mar 2013, Simon Jeons wrote:
>
>>> This has nothing to do with this thread, but /proc/vmstat actually does
>>> not include the MemTotal value being discussed in this thread that
>>> /proc/meminfo does.  /proc/meminfo is typically the interface used by
>>> applications, probably mostly for historical purposes since both are
>> Do you mean /proc/vmstat is not used by  applications.
>> sar -B 1
>> pgpgin/s pgpgout/s   fault/s  majflt/s  pgfree/s pgscank/s pgscand/s pgsteal/s
>> %vmeff
>> I think they are read from /proc/vmstat
>>
> Yes, there is userspace code that parses /proc/vmstat.

Then why both need /proc/meminfo and /proc/vmstat?

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Re: [Bug 53501] New: Duplicated MemTotal with different values

[David Rientjes]

On Tue, 5 Mar 2013, Simon Jeons wrote:

> Then why both need /proc/meminfo and /proc/vmstat?
> 

Because we do not break userspace.

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