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[PATCH 2/2] mm, memory_hotplug: remove zone restrictions

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  [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Michal Hocko <mhocko@kernel.org> - 2017-06-29 09:40 +0200
    Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Joonsoo Kim <js1304@gmail.com> - 2017-06-30 03:20 +0200
    Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Wei Yang <richard.weiyang@gmail.com> - 2017-06-30 05:20 +0200
      Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Michal Hocko <mhocko@kernel.org> - 2017-06-30 10:40 +0200
        Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Wei Yang <richard.weiyang@gmail.com> - 2017-06-30 11:50 +0200
          Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Michal Hocko <mhocko@kernel.org> - 2017-06-30 12:00 +0200
            Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Michal Hocko <mhocko@kernel.org> - 2017-06-30 13:10 +0200

#1677485 — [PATCH 2/2] mm, memory_hotplug: remove zone restrictions

From: Michal Hocko <mhocko@suse.com>

Historically we have enforced that any kernel zone (e.g ZONE_NORMAL) has
to precede the Movable zone in the physical memory range. The purpose of
the movable zone is, however, not bound to any physical memory restriction.
It merely defines a class of migrateable and reclaimable memory.

There are users (e.g. CMA) who might want to reserve specific physical
memory ranges for their own purpose. Moreover our pfn walkers have to be
prepared for zones overlapping in the physical range already because we
do support interleaving NUMA nodes and therefore zones can interleave as
well. This means we can allow each memory block to be associated with a
different zone.

Loosen the current onlining semantic and allow explicit onlining type on
any memblock. That means that online_{kernel,movable} will be allowed
regardless of the physical address of the memblock as long as it is
offline of course. This might result in moveble zone overlapping with
other kernel zones. Default onlining then becomes a bit tricky but still
sensible. echo online > memoryXY/state will online the given block to
	1) the default zone if the given range is outside of any zone
	2) the enclosing zone if such a zone doesn't interleave with
	   any other zone
        3) the default zone if more zones interleave for this range
where default zone is movable zone only if movable_node is enabled
otherwise it is a kernel zone.

Here is an example of the semantic with (movable_node is not present but
it work in an analogous way). We start with following memblocks, all of
them offline
memory34/valid_zones:Normal Movable
memory35/valid_zones:Normal Movable
memory36/valid_zones:Normal Movable
memory37/valid_zones:Normal Movable
memory38/valid_zones:Normal Movable
memory39/valid_zones:Normal Movable
memory40/valid_zones:Normal Movable
memory41/valid_zones:Normal Movable

Now, we online block 34 in default mode and block 37 as movable
root@test1:/sys/devices/system/node/node1# echo online > memory34/state
root@test1:/sys/devices/system/node/node1# echo online_movable > memory37/state
memory34/valid_zones:Normal
memory35/valid_zones:Normal Movable
memory36/valid_zones:Normal Movable
memory37/valid_zones:Movable
memory38/valid_zones:Normal Movable
memory39/valid_zones:Normal Movable
memory40/valid_zones:Normal Movable
memory41/valid_zones:Normal Movable

As we can see all other blocks can still be onlined both into Normal and
Movable zones and the Normal is default because the Movable zone spans
only block37 now.
root@test1:/sys/devices/system/node/node1# echo online_movable > memory41/state
memory34/valid_zones:Normal
memory35/valid_zones:Normal Movable
memory36/valid_zones:Normal Movable
memory37/valid_zones:Movable
memory38/valid_zones:Movable Normal
memory39/valid_zones:Movable Normal
memory40/valid_zones:Movable Normal
memory41/valid_zones:Movable

Now the default zone for blocks 37-41 has changed because movable zone
spans that range.
root@test1:/sys/devices/system/node/node1# echo online_kernel > memory39/state
memory34/valid_zones:Normal
memory35/valid_zones:Normal Movable
memory36/valid_zones:Normal Movable
memory37/valid_zones:Movable
memory38/valid_zones:Normal Movable
memory39/valid_zones:Normal
memory40/valid_zones:Movable Normal
memory41/valid_zones:Movable

Note that the block 39 now belongs to the zone Normal and so block38
falls into Normal by default as well.

For completness
root@test1:/sys/devices/system/node/node1# for i in memory[34]?
do
	echo online > $i/state 2>/dev/null
done

memory34/valid_zones:Normal
memory35/valid_zones:Normal
memory36/valid_zones:Normal
memory37/valid_zones:Movable
memory38/valid_zones:Normal
memory39/valid_zones:Normal
memory40/valid_zones:Movable
memory41/valid_zones:Movable

Implementation wise the change is quite straightforward. We can get rid
of allow_online_pfn_range altogether. online_pages allows only offline
nodes already. The original default_zone_for_pfn will become
default_kernel_zone_for_pfn. New default_zone_for_pfn implements the
above semantic. zone_for_pfn_range is slightly reorganized to implement
kernel and movable online type explicitly and MMOP_ONLINE_KEEP becomes
a catch all default behavior.

Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 drivers/base/memory.c |  3 ---
 mm/memory_hotplug.c   | 74 ++++++++++++++++-----------------------------------
 2 files changed, 23 insertions(+), 54 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 26383af9900c..4e3b61cda520 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -394,9 +394,6 @@ static void print_allowed_zone(char *buf, int nid, unsigned long start_pfn,
 {
 	struct zone *zone;
 
-	if (!allow_online_pfn_range(nid, start_pfn, nr_pages, online_type))
-		return;
-
 	zone = zone_for_pfn_range(online_type, nid, start_pfn, nr_pages);
 	if (zone != default_zone) {
 		strcat(buf, " ");
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6b9a60115e37..670f7acbecf4 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -894,7 +894,7 @@ void __ref move_pfn_range_to_zone(struct zone *zone,
  * If no kernel zone covers this pfn range it will automatically go
  * to the ZONE_NORMAL.
  */
-static struct zone *default_zone_for_pfn(int nid, unsigned long start_pfn,
+static struct zone *default_kernel_zone_for_pfn(int nid, unsigned long start_pfn,
 		unsigned long nr_pages)
 {
 	struct pglist_data *pgdat = NODE_DATA(nid);
@@ -910,65 +910,40 @@ static struct zone *default_zone_for_pfn(int nid, unsigned long start_pfn,
 	return &pgdat->node_zones[ZONE_NORMAL];
 }
 
-bool allow_online_pfn_range(int nid, unsigned long pfn, unsigned long nr_pages, int online_type)
+static inline struct zone *default_zone_for_pfn(int nid, unsigned long start_pfn,
+		unsigned long nr_pages)
 {
-	struct pglist_data *pgdat = NODE_DATA(nid);
-	struct zone *movable_zone = &pgdat->node_zones[ZONE_MOVABLE];
-	struct zone *default_zone = default_zone_for_pfn(nid, pfn, nr_pages);
+	struct zone *kernel_zone = default_kernel_zone_for_pfn(nid, start_pfn,
+			nr_pages);
+	struct zone *movable_zone = &NODE_DATA(nid)->node_zones[ZONE_MOVABLE];
+	bool in_kernel = zone_intersects(kernel_zone, start_pfn, nr_pages);
+	bool in_movable = zone_intersects(movable_zone, start_pfn, nr_pages);
 
 	/*
-	 * TODO there shouldn't be any inherent reason to have ZONE_NORMAL
-	 * physically before ZONE_MOVABLE. All we need is they do not
-	 * overlap. Historically we didn't allow ZONE_NORMAL after ZONE_MOVABLE
-	 * though so let's stick with it for simplicity for now.
-	 * TODO make sure we do not overlap with ZONE_DEVICE
+	 * We inherit the existing zone in a simple case where zones do not
+	 * overlap in the given range
 	 */
-	if (online_type == MMOP_ONLINE_KERNEL) {
-		if (zone_is_empty(movable_zone))
-			return true;
-		return movable_zone->zone_start_pfn >= pfn + nr_pages;
-	} else if (online_type == MMOP_ONLINE_MOVABLE) {
-		return zone_end_pfn(default_zone) <= pfn;
-	}
-
-	/* MMOP_ONLINE_KEEP will always succeed and inherits the current zone */
-	return online_type == MMOP_ONLINE_KEEP;
-}
-
-static inline bool movable_pfn_range(int nid, struct zone *default_zone,
-		unsigned long start_pfn, unsigned long nr_pages)
-{
-	if (!allow_online_pfn_range(nid, start_pfn, nr_pages,
-				MMOP_ONLINE_KERNEL))
-		return true;
-
-	if (!movable_node_is_enabled())
-		return false;
+	if (in_kernel ^ in_movable)
+		return (in_kernel) ? kernel_zone : movable_zone;
 
-	return !zone_intersects(default_zone, start_pfn, nr_pages);
+	/*
+	 * If the range doesn't belong to any zone or two zones overlap in the
+	 * given range then we use movable zone only if movable_node is
+	 * enabled because we always online to a kernel zone by default.
+	 */
+	return movable_node_enabled ? movable_zone : kernel_zone;
 }
 
 struct zone * zone_for_pfn_range(int online_type, int nid, unsigned start_pfn,
 		unsigned long nr_pages)
 {
-	struct pglist_data *pgdat = NODE_DATA(nid);
-	struct zone *zone = default_zone_for_pfn(nid, start_pfn, nr_pages);
+	if (online_type == MMOP_ONLINE_KERNEL)
+		return default_kernel_zone_for_pfn(nid, start_pfn, nr_pages);
 
-	if (online_type == MMOP_ONLINE_KEEP) {
-		struct zone *movable_zone = &pgdat->node_zones[ZONE_MOVABLE];
-		/*
-		 * MMOP_ONLINE_KEEP defaults to MMOP_ONLINE_KERNEL but use
-		 * movable zone if that is not possible (e.g. we are within
-		 * or past the existing movable zone). movable_node overrides
-		 * this default and defaults to movable zone
-		 */
-		if (movable_pfn_range(nid, zone, start_pfn, nr_pages))
-			zone = movable_zone;
-	} else if (online_type == MMOP_ONLINE_MOVABLE) {
-		zone = &pgdat->node_zones[ZONE_MOVABLE];
-	}
+	if (online_type == MMOP_ONLINE_MOVABLE)
+		return &NODE_DATA(nid)->node_zones[ZONE_MOVABLE];
 
-	return zone;
+	return default_zone_for_pfn(nid, start_pfn, nr_pages);
 }
 
 /*
@@ -997,9 +972,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	struct memory_notify arg;
 
 	nid = pfn_to_nid(pfn);
-	if (!allow_online_pfn_range(nid, pfn, nr_pages, online_type))
-		return -EINVAL;
-
 	/* associate pfn range with the zone */
 	zone = move_pfn_range(online_type, nid, pfn, nr_pages);
 
-- 
2.11.0

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#1678368

On Thu, Jun 29, 2017 at 09:35:09AM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> Historically we have enforced that any kernel zone (e.g ZONE_NORMAL) has
> to precede the Movable zone in the physical memory range. The purpose of
> the movable zone is, however, not bound to any physical memory restriction.
> It merely defines a class of migrateable and reclaimable memory.
> 
> There are users (e.g. CMA) who might want to reserve specific physical
> memory ranges for their own purpose. Moreover our pfn walkers have to be
> prepared for zones overlapping in the physical range already because we
> do support interleaving NUMA nodes and therefore zones can interleave as
> well. This means we can allow each memory block to be associated with a
> different zone.
> 
> Loosen the current onlining semantic and allow explicit onlining type on
> any memblock. That means that online_{kernel,movable} will be allowed
> regardless of the physical address of the memblock as long as it is
> offline of course. This might result in moveble zone overlapping with
> other kernel zones. Default onlining then becomes a bit tricky but still
> sensible. echo online > memoryXY/state will online the given block to
> 	1) the default zone if the given range is outside of any zone
> 	2) the enclosing zone if such a zone doesn't interleave with
> 	   any other zone
>         3) the default zone if more zones interleave for this range
> where default zone is movable zone only if movable_node is enabled
> otherwise it is a kernel zone.
> 
> Here is an example of the semantic with (movable_node is not present but
> it work in an analogous way). We start with following memblocks, all of
> them offline
> memory34/valid_zones:Normal Movable
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Normal Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal Movable
> memory40/valid_zones:Normal Movable
> memory41/valid_zones:Normal Movable
> 
> Now, we online block 34 in default mode and block 37 as movable
> root@test1:/sys/devices/system/node/node1# echo online > memory34/state
> root@test1:/sys/devices/system/node/node1# echo online_movable > memory37/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal Movable
> memory40/valid_zones:Normal Movable
> memory41/valid_zones:Normal Movable
> 
> As we can see all other blocks can still be onlined both into Normal and
> Movable zones and the Normal is default because the Movable zone spans
> only block37 now.
> root@test1:/sys/devices/system/node/node1# echo online_movable > memory41/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Movable Normal
> memory39/valid_zones:Movable Normal
> memory40/valid_zones:Movable Normal
> memory41/valid_zones:Movable
> 
> Now the default zone for blocks 37-41 has changed because movable zone
> spans that range.
> root@test1:/sys/devices/system/node/node1# echo online_kernel > memory39/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal
> memory40/valid_zones:Movable Normal
> memory41/valid_zones:Movable
> 
> Note that the block 39 now belongs to the zone Normal and so block38
> falls into Normal by default as well.
> 
> For completness
> root@test1:/sys/devices/system/node/node1# for i in memory[34]?
> do
> 	echo online > $i/state 2>/dev/null
> done
> 
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal
> memory36/valid_zones:Normal
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal
> memory39/valid_zones:Normal
> memory40/valid_zones:Movable
> memory41/valid_zones:Movable
> 
> Implementation wise the change is quite straightforward. We can get rid
> of allow_online_pfn_range altogether. online_pages allows only offline
> nodes already. The original default_zone_for_pfn will become
> default_kernel_zone_for_pfn. New default_zone_for_pfn implements the
> above semantic. zone_for_pfn_range is slightly reorganized to implement
> kernel and movable online type explicitly and MMOP_ONLINE_KEEP becomes
> a catch all default behavior.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.com>

I appreaciate your help!

Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Thanks.

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#1678426

On Thu, Jun 29, 2017 at 3:35 PM, Michal Hocko <mhocko@kernel.org> wrote:
> From: Michal Hocko <mhocko@suse.com>
>

Michal,

I love the idea very much.

> Historically we have enforced that any kernel zone (e.g ZONE_NORMAL) has
> to precede the Movable zone in the physical memory range. The purpose of
> the movable zone is, however, not bound to any physical memory restriction.
> It merely defines a class of migrateable and reclaimable memory.
>
> There are users (e.g. CMA) who might want to reserve specific physical
> memory ranges for their own purpose. Moreover our pfn walkers have to be
> prepared for zones overlapping in the physical range already because we
> do support interleaving NUMA nodes and therefore zones can interleave as
> well. This means we can allow each memory block to be associated with a
> different zone.
>
> Loosen the current onlining semantic and allow explicit onlining type on
> any memblock. That means that online_{kernel,movable} will be allowed
> regardless of the physical address of the memblock as long as it is
> offline of course. This might result in moveble zone overlapping with
> other kernel zones. Default onlining then becomes a bit tricky but still

As here mentioned, we just remove the restriction for zone_movable.
For other zones, we still keep the restriction and the order as before.

Maybe the title is a little misleading. Audience may thinks no restriction
for all zones.

> sensible. echo online > memoryXY/state will online the given block to
>         1) the default zone if the given range is outside of any zone
>         2) the enclosing zone if such a zone doesn't interleave with
>            any other zone
>         3) the default zone if more zones interleave for this range
> where default zone is movable zone only if movable_node is enabled
> otherwise it is a kernel zone.
>
> Here is an example of the semantic with (movable_node is not present but
> it work in an analogous way). We start with following memblocks, all of
> them offline
> memory34/valid_zones:Normal Movable
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Normal Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal Movable
> memory40/valid_zones:Normal Movable
> memory41/valid_zones:Normal Movable
>
> Now, we online block 34 in default mode and block 37 as movable
> root@test1:/sys/devices/system/node/node1# echo online > memory34/state
> root@test1:/sys/devices/system/node/node1# echo online_movable > memory37/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal Movable
> memory40/valid_zones:Normal Movable
> memory41/valid_zones:Normal Movable
>
> As we can see all other blocks can still be onlined both into Normal and
> Movable zones and the Normal is default because the Movable zone spans
> only block37 now.
> root@test1:/sys/devices/system/node/node1# echo online_movable > memory41/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Movable Normal
> memory39/valid_zones:Movable Normal
> memory40/valid_zones:Movable Normal
> memory41/valid_zones:Movable
>

As I spotted on the previous patch, after several round of online/offline,
The output of valid_zones will differ.

For example in this case, after I offline memory37 and 41, I expect this:

 memory34/valid_zones:Normal
 memory35/valid_zones:Normal Movable
 memory36/valid_zones:Normal Movable
 memory37/valid_zones:Normal Movable
 memory38/valid_zones:Normal Movable
 memory39/valid_zones:Normal Movable
 memory40/valid_zones:Normal Movable
 memory41/valid_zones:Normal Movable

While the current result would be

 memory34/valid_zones:Normal
 memory35/valid_zones:Normal Movable
 memory36/valid_zones:Normal Movable
 memory37/valid_zones:Movable Normal
 memory38/valid_zones:Movable Normal
 memory39/valid_zones:Movable Normal
 memory40/valid_zones:Movable Normal
 memory41/valid_zones:Movable Normal

The reason is the same, we don't adjust the zone's range when offline
memory.

This is also a known issue?

> Now the default zone for blocks 37-41 has changed because movable zone
> spans that range.
> root@test1:/sys/devices/system/node/node1# echo online_kernel > memory39/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal
> memory40/valid_zones:Movable Normal
> memory41/valid_zones:Movable
>
> Note that the block 39 now belongs to the zone Normal and so block38
> falls into Normal by default as well.
>
> For completness
> root@test1:/sys/devices/system/node/node1# for i in memory[34]?
> do
>         echo online > $i/state 2>/dev/null
> done
>
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal
> memory36/valid_zones:Normal
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal
> memory39/valid_zones:Normal
> memory40/valid_zones:Movable
> memory41/valid_zones:Movable
>
> Implementation wise the change is quite straightforward. We can get rid
> of allow_online_pfn_range altogether. online_pages allows only offline
> nodes already. The original default_zone_for_pfn will become
> default_kernel_zone_for_pfn. New default_zone_for_pfn implements the
> above semantic. zone_for_pfn_range is slightly reorganized to implement
> kernel and movable online type explicitly and MMOP_ONLINE_KEEP becomes
> a catch all default behavior.
>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---

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#1678598

On Fri 30-06-17 11:09:51, Wei Yang wrote:
> On Thu, Jun 29, 2017 at 3:35 PM, Michal Hocko <mhocko@kernel.org> wrote:
> > From: Michal Hocko <mhocko@suse.com>
> >
> 
> Michal,
> 
> I love the idea very much.
> 
> > Historically we have enforced that any kernel zone (e.g ZONE_NORMAL) has
> > to precede the Movable zone in the physical memory range. The purpose of
> > the movable zone is, however, not bound to any physical memory restriction.
> > It merely defines a class of migrateable and reclaimable memory.
> >
> > There are users (e.g. CMA) who might want to reserve specific physical
> > memory ranges for their own purpose. Moreover our pfn walkers have to be
> > prepared for zones overlapping in the physical range already because we
> > do support interleaving NUMA nodes and therefore zones can interleave as
> > well. This means we can allow each memory block to be associated with a
> > different zone.
> >
> > Loosen the current onlining semantic and allow explicit onlining type on
> > any memblock. That means that online_{kernel,movable} will be allowed
> > regardless of the physical address of the memblock as long as it is
> > offline of course. This might result in moveble zone overlapping with
> > other kernel zones. Default onlining then becomes a bit tricky but still
> 
> As here mentioned, we just remove the restriction for zone_movable.
> For other zones, we still keep the restriction and the order as before.

All other zones except for ZONE_NORMAL are subject of the physical
memory restrictions.
 
> Maybe the title is a little misleading. Audience may thinks no restriction
> for all zones.

I thought the context was clear from the fact that this is a hotplug
related patch. As such we do not allow online_{dma,dma32,normal} we only
allow to online into a kernel zone. I can update the wording but do not
have a good idea how.

[...]
> As I spotted on the previous patch, after several round of online/offline,
> The output of valid_zones will differ.
> 
> For example in this case, after I offline memory37 and 41, I expect this:
> 
>  memory34/valid_zones:Normal
>  memory35/valid_zones:Normal Movable
>  memory36/valid_zones:Normal Movable
>  memory37/valid_zones:Normal Movable
>  memory38/valid_zones:Normal Movable
>  memory39/valid_zones:Normal Movable
>  memory40/valid_zones:Normal Movable
>  memory41/valid_zones:Normal Movable
> 
> While the current result would be
> 
>  memory34/valid_zones:Normal
>  memory35/valid_zones:Normal Movable
>  memory36/valid_zones:Normal Movable
>  memory37/valid_zones:Movable Normal
>  memory38/valid_zones:Movable Normal
>  memory39/valid_zones:Movable Normal
>  memory40/valid_zones:Movable Normal
>  memory41/valid_zones:Movable Normal

You haven't written your sequence of onlining but if you used the same
one as mentioned in the patch then you should get
memory34/valid_zones:Normal
memory35/valid_zones:Normal Movable
memory36/valid_zones:Normal Movable
memory37/valid_zones:Normal Movable
memory38/valid_zones:Normal Movable
memory39/valid_zones:Normal
memory40/valid_zones:Movable Normal
memory41/valid_zones:Movable Normal

Even if you kept 37 as movable and offline 38 you wouldn't get 38-41
movable by default because...

> The reason is the same, we don't adjust the zone's range when offline
> memory.

.. of this.

> This is also a known issue?

yes and to be honest I do not plan to fix it unless somebody has a real
life usecase for it. Now that we allow explicit onlininig type anywhere
it seems like a reasonable behavior and this will allow us to remove
quite some code which is always a good deal wrt longterm maintenance.

Thanks!
-- 
Michal Hocko
SUSE Labs

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#1678639

On Fri, Jun 30, 2017 at 4:39 PM, Michal Hocko <mhocko@kernel.org> wrote:
> On Fri 30-06-17 11:09:51, Wei Yang wrote:
>> On Thu, Jun 29, 2017 at 3:35 PM, Michal Hocko <mhocko@kernel.org> wrote:
>> > From: Michal Hocko <mhocko@suse.com>
>> >
>>
>> Michal,
>>
>> I love the idea very much.
>>

>
> You haven't written your sequence of onlining but if you used the same
> one as mentioned in the patch then you should get
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Normal Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal
> memory40/valid_zones:Movable Normal
> memory41/valid_zones:Movable Normal
>
> Even if you kept 37 as movable and offline 38 you wouldn't get 38-41
> movable by default because...
>

Yes, it depends on the zone range.

>> The reason is the same, we don't adjust the zone's range when offline
>> memory.
>
> .. of this.
>
>> This is also a known issue?
>
> yes and to be honest I do not plan to fix it unless somebody has a real
> life usecase for it. Now that we allow explicit onlininig type anywhere
> it seems like a reasonable behavior and this will allow us to remove
> quite some code which is always a good deal wrt longterm maintenance.
>

hmm... the statistics displayed in /proc/zoneinfo would be meaningless
for zone_normal and zone_movable.

I am not sure, maybe no one care about these fields.

> Thanks!
> --
> Michal Hocko
> SUSE Labs

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#1678644

On Fri 30-06-17 17:39:56, Wei Yang wrote:
> On Fri, Jun 30, 2017 at 4:39 PM, Michal Hocko <mhocko@kernel.org> wrote:
[...]
> > yes and to be honest I do not plan to fix it unless somebody has a real
> > life usecase for it. Now that we allow explicit onlininig type anywhere
> > it seems like a reasonable behavior and this will allow us to remove
> > quite some code which is always a good deal wrt longterm maintenance.
> >
> 
> hmm... the statistics displayed in /proc/zoneinfo would be meaningless
> for zone_normal and zone_movable.

Why would they be meaningless? Counters will always reflect the actual
use - if not then it is a bug. And wrt to zone description what is
meaningless about
memory34/valid_zones:Normal
memory35/valid_zones:Normal Movable
memory36/valid_zones:Movable
memory37/valid_zones:Movable Normal
memory38/valid_zones:Movable Normal
memory39/valid_zones:Movable Normal
memory40/valid_zones:Normal
memory41/valid_zones:Movable

And
Node 1, zone   Normal
  pages free     65465
        min      156
        low      221
        high     286
        spanned  229376
        present  65536
        managed  65536
[...]
  start_pfn:           1114112
Node 1, zone  Movable
  pages free     65443
        min      156
        low      221
        high     286
        spanned  196608
        present  65536
        managed  65536
[...]
  start_pfn:           1179648

ranges are clearly defined as [start_pfn, start_pfn+managed] and managed
matches the number of onlined pages (256MB).
-- 
Michal Hocko
SUSE Labs

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#1678697

On Fri 30-06-17 11:55:45, Michal Hocko wrote:
> On Fri 30-06-17 17:39:56, Wei Yang wrote:
> > On Fri, Jun 30, 2017 at 4:39 PM, Michal Hocko <mhocko@kernel.org> wrote:
> [...]
> > > yes and to be honest I do not plan to fix it unless somebody has a real
> > > life usecase for it. Now that we allow explicit onlininig type anywhere
> > > it seems like a reasonable behavior and this will allow us to remove
> > > quite some code which is always a good deal wrt longterm maintenance.
> > >
> > 
> > hmm... the statistics displayed in /proc/zoneinfo would be meaningless
> > for zone_normal and zone_movable.
> 
> Why would they be meaningless? Counters will always reflect the actual
> use - if not then it is a bug. And wrt to zone description what is
> meaningless about
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Movable
> memory37/valid_zones:Movable Normal
> memory38/valid_zones:Movable Normal
> memory39/valid_zones:Movable Normal
> memory40/valid_zones:Normal
> memory41/valid_zones:Movable
> 
> And
> Node 1, zone   Normal
>   pages free     65465
>         min      156
>         low      221
>         high     286
>         spanned  229376
>         present  65536
>         managed  65536
> [...]
>   start_pfn:           1114112
> Node 1, zone  Movable
>   pages free     65443
>         min      156
>         low      221
>         high     286
>         spanned  196608
>         present  65536
>         managed  65536
> [...]
>   start_pfn:           1179648
> 
> ranges are clearly defined as [start_pfn, start_pfn+managed] and managed

errr, this should be [start_pfn, start_pfn + spanned] of course.

> matches the number of onlined pages (256MB).

-- 
Michal Hocko
SUSE Labs

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