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SubjectRe: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions
Are there any other concerns regarding this patch? Can I repost it for
inclusion?

On Thu 29-06-17 09:35:09, 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>
> ---
> 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
>

--
Michal Hocko
SUSE Labs

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