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[PATCH 3/4] mm: unify new_node_page and alloc_migrate_target

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  [PATCH 3/4] mm: unify new_node_page and alloc_migrate_target Michal Hocko <mhocko@kernel.org> - 2017-06-08 09:50 +0200
    Re: [PATCH 3/4] mm: unify new_node_page and alloc_migrate_target Vlastimil Babka <vbabka@suse.cz> - 2017-06-08 10:40 +0200
      Re: [PATCH 3/4] mm: unify new_node_page and alloc_migrate_target Michal Hocko <mhocko@kernel.org> - 2017-06-08 10:50 +0200

#1660868 — [PATCH 3/4] mm: unify new_node_page and alloc_migrate_target

From: Michal Hocko <mhocko@suse.com>

394e31d2ceb4 ("mem-hotplug: alloc new page from a nearest neighbor node
when mem-offline") has duplicated a large part of alloc_migrate_target
with some hotplug specific special casing. To be more precise it tried
to enfore the allocation from a different node than the original page.
As a result the two function diverged in their shared logic, e.g. the
hugetlb allocation strategy. Let's unify the two and express different
NUMA requirements by the given nodemask. new_node_page will simply
exclude the node it doesn't care about and alloc_migrate_target will
use all the available nodes. alloc_migrate_target will then learn to
migrate hugetlb pages more sanely and use preallocated pool when
possible.

Please note that alloc_migrate_target used to call alloc_page resp.
alloc_pages_current so the memory policy of the current context which
is quite strange when we consider that it is used in the context of
alloc_contig_range which just tries to migrate pages which stand in the
way.

Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 include/linux/migrate.h | 17 +++++++++++++++++
 mm/memory_hotplug.c     | 11 +----------
 mm/page_isolation.c     | 18 ++----------------
 3 files changed, 20 insertions(+), 26 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 48e24844b3c5..f80c9882403a 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -4,6 +4,7 @@
 #include <linux/mm.h>
 #include <linux/mempolicy.h>
 #include <linux/migrate_mode.h>
+#include <linux/hugetlb.h>
 
 typedef struct page *new_page_t(struct page *page, unsigned long private,
 				int **reason);
@@ -30,6 +31,22 @@ enum migrate_reason {
 /* In mm/debug.c; also keep sync with include/trace/events/migrate.h */
 extern char *migrate_reason_names[MR_TYPES];
 
+static inline struct page *new_page_nodemask(struct page *page, int preferred_nid,
+		nodemask_t *nodemask)
+{
+	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
+
+	if (PageHuge(page))
+		return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
+				nodemask);
+
+	if (PageHighMem(page)
+	    || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
+		gfp_mask |= __GFP_HIGHMEM;
+
+	return __alloc_pages_nodemask(gfp_mask, 0, preferred_nid, nodemask);
+}
+
 #ifdef CONFIG_MIGRATION
 
 extern void putback_movable_pages(struct list_head *l);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6e0d964ac561..d2f13f2f3ebf 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1429,7 +1429,6 @@ static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
 static struct page *new_node_page(struct page *page, unsigned long private,
 		int **result)
 {
-	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
 	int nid = page_to_nid(page);
 	nodemask_t nmask = node_states[N_MEMORY];
 
@@ -1442,15 +1441,7 @@ static struct page *new_node_page(struct page *page, unsigned long private,
 	if (nodes_empty(nmask))
 		node_set(nid, nmask);
 
-	if (PageHuge(page))
-		return alloc_huge_page_nodemask(
-				page_hstate(compound_head(page)), &nmask);
-
-	if (PageHighMem(page)
-	    || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
-		gfp_mask |= __GFP_HIGHMEM;
-
-	return __alloc_pages_nodemask(gfp_mask, 0, nid, &nmask);
+	return new_page_nodemask(page, nid, &nmask);
 }
 
 #define NR_OFFLINE_AT_ONCE_PAGES	(256)
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 3606104893e0..757410d9f758 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -8,6 +8,7 @@
 #include <linux/memory.h>
 #include <linux/hugetlb.h>
 #include <linux/page_owner.h>
+#include <linux/migrate.h>
 #include "internal.h"
 
 #define CREATE_TRACE_POINTS
@@ -294,20 +295,5 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 struct page *alloc_migrate_target(struct page *page, unsigned long private,
 				  int **resultp)
 {
-	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
-
-	/*
-	 * TODO: allocate a destination hugepage from a nearest neighbor node,
-	 * accordance with memory policy of the user process if possible. For
-	 * now as a simple work-around, we use the next node for destination.
-	 */
-	if (PageHuge(page))
-		return alloc_huge_page_node(page_hstate(compound_head(page)),
-					    next_node_in(page_to_nid(page),
-							 node_online_map));
-
-	if (PageHighMem(page))
-		gfp_mask |= __GFP_HIGHMEM;
-
-	return alloc_page(gfp_mask);
+	return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);
 }
-- 
2.11.0

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#1660937

On 06/08/2017 09:45 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> 394e31d2ceb4 ("mem-hotplug: alloc new page from a nearest neighbor node
> when mem-offline") has duplicated a large part of alloc_migrate_target
> with some hotplug specific special casing. To be more precise it tried
> to enfore the allocation from a different node than the original page.
> As a result the two function diverged in their shared logic, e.g. the
> hugetlb allocation strategy. Let's unify the two and express different
> NUMA requirements by the given nodemask. new_node_page will simply
> exclude the node it doesn't care about and alloc_migrate_target will
> use all the available nodes. alloc_migrate_target will then learn to
> migrate hugetlb pages more sanely and use preallocated pool when
> possible.
> 
> Please note that alloc_migrate_target used to call alloc_page resp.
> alloc_pages_current so the memory policy of the current context which
> is quite strange when we consider that it is used in the context of
> alloc_contig_range which just tries to migrate pages which stand in the
> way.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 3606104893e0..757410d9f758 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -8,6 +8,7 @@
>  #include <linux/memory.h>
>  #include <linux/hugetlb.h>
>  #include <linux/page_owner.h>
> +#include <linux/migrate.h>
>  #include "internal.h"
>  
>  #define CREATE_TRACE_POINTS
> @@ -294,20 +295,5 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
>  struct page *alloc_migrate_target(struct page *page, unsigned long private,
>  				  int **resultp)
>  {
> -	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
> -
> -	/*
> -	 * TODO: allocate a destination hugepage from a nearest neighbor node,
> -	 * accordance with memory policy of the user process if possible. For
> -	 * now as a simple work-around, we use the next node for destination.
> -	 */
> -	if (PageHuge(page))
> -		return alloc_huge_page_node(page_hstate(compound_head(page)),
> -					    next_node_in(page_to_nid(page),
> -							 node_online_map));
> -
> -	if (PageHighMem(page))
> -		gfp_mask |= __GFP_HIGHMEM;
> -
> -	return alloc_page(gfp_mask);
> +	return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);

This replaces the N_ONLINE (node_online_map) with N_MEMORY for huge
pages. Assuming that's OK.

>  }
> 

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#1660952

On Thu 08-06-17 10:36:13, Vlastimil Babka wrote:
> On 06/08/2017 09:45 AM, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> > 
> > 394e31d2ceb4 ("mem-hotplug: alloc new page from a nearest neighbor node
> > when mem-offline") has duplicated a large part of alloc_migrate_target
> > with some hotplug specific special casing. To be more precise it tried
> > to enfore the allocation from a different node than the original page.
> > As a result the two function diverged in their shared logic, e.g. the
> > hugetlb allocation strategy. Let's unify the two and express different
> > NUMA requirements by the given nodemask. new_node_page will simply
> > exclude the node it doesn't care about and alloc_migrate_target will
> > use all the available nodes. alloc_migrate_target will then learn to
> > migrate hugetlb pages more sanely and use preallocated pool when
> > possible.
> > 
> > Please note that alloc_migrate_target used to call alloc_page resp.
> > alloc_pages_current so the memory policy of the current context which
> > is quite strange when we consider that it is used in the context of
> > alloc_contig_range which just tries to migrate pages which stand in the
> > way.
> > 
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> Acked-by: Vlastimil Babka <vbabka@suse.cz>

Thanks!

> > diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> > index 3606104893e0..757410d9f758 100644
> > --- a/mm/page_isolation.c
> > +++ b/mm/page_isolation.c
> > @@ -8,6 +8,7 @@
> >  #include <linux/memory.h>
> >  #include <linux/hugetlb.h>
> >  #include <linux/page_owner.h>
> > +#include <linux/migrate.h>
> >  #include "internal.h"
> >  
> >  #define CREATE_TRACE_POINTS
> > @@ -294,20 +295,5 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
> >  struct page *alloc_migrate_target(struct page *page, unsigned long private,
> >  				  int **resultp)
> >  {
> > -	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
> > -
> > -	/*
> > -	 * TODO: allocate a destination hugepage from a nearest neighbor node,
> > -	 * accordance with memory policy of the user process if possible. For
> > -	 * now as a simple work-around, we use the next node for destination.
> > -	 */
> > -	if (PageHuge(page))
> > -		return alloc_huge_page_node(page_hstate(compound_head(page)),
> > -					    next_node_in(page_to_nid(page),
> > -							 node_online_map));
> > -
> > -	if (PageHighMem(page))
> > -		gfp_mask |= __GFP_HIGHMEM;
> > -
> > -	return alloc_page(gfp_mask);
> > +	return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);
> 
> This replaces the N_ONLINE (node_online_map) with N_MEMORY for huge
> pages. Assuming that's OK.

Yes, this is what 231e97e2b8ec ("mem-hotplug: use nodes that contain
memory as mask in new_node_page()") fixed in new_node_page and didn't
care to do on alloc_migrate_target. Another argument to remove the code
duplication. Thanks for pointing out anyway!

-- 
Michal Hocko
SUSE Labs

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