Huge pages are not movable so are not allocated from ZONE_MOVABLE. However,
as ZONE_MOVABLE will always have pages that can be migrated or reclaimed,
it can be used to satisfy hugepage allocations even when the system has been
running a long time. This allows an administrator to resize the hugepage
pool at runtime depending on the size of ZONE_MOVABLE.

This patch adds a new sysctl called hugepages_treat_as_movable. When
a non-zero value is written to it, future allocations for the huge page
pool will use ZONE_MOVABLE. Despite huge pages being non-movable, we do not
introduce additional external fragmentation of note as huge pages are always
the largest contiguous block we care about.

Signed-off-by: Mel Gorman <[EMAIL PROTECTED]>
---

 include/linux/hugetlb.h   |    3 +++
 include/linux/mempolicy.h |    6 +++---
 include/linux/sysctl.h    |    1 +
 kernel/sysctl.c           |    8 ++++++++
 mm/hugetlb.c              |   23 ++++++++++++++++++++---
 mm/mempolicy.c            |    5 +++--
 6 files changed, 38 insertions(+), 8 deletions(-)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.20-rc4-mm1-002_create_movable_zone/include/linux/hugetlb.h 
linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/include/linux/hugetlb.h
--- linux-2.6.20-rc4-mm1-002_create_movable_zone/include/linux/hugetlb.h        
2007-01-07 05:45:51.000000000 +0000
+++ linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/include/linux/hugetlb.h     
2007-01-25 17:34:15.000000000 +0000
@@ -14,6 +14,7 @@ static inline int is_vm_hugetlb_page(str
 }
 
 int hugetlb_sysctl_handler(struct ctl_table *, int, struct file *, void __user 
*, size_t *, loff_t *);
+int hugetlb_treat_movable_handler(struct ctl_table *, int, struct file *, void 
__user *, size_t *, loff_t *);
 int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct 
vm_area_struct *);
 int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct 
page **, struct vm_area_struct **, unsigned long *, int *, int);
 void unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned 
long);
@@ -28,6 +29,8 @@ int hugetlb_reserve_pages(struct inode *
 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed);
 
 extern unsigned long max_huge_pages;
+extern unsigned long hugepages_treat_as_movable;
+extern gfp_t htlb_alloc_mask;
 extern const unsigned long hugetlb_zero, hugetlb_infinity;
 extern int sysctl_hugetlb_shm_group;
 
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.20-rc4-mm1-002_create_movable_zone/include/linux/mempolicy.h 
linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/include/linux/mempolicy.h
--- linux-2.6.20-rc4-mm1-002_create_movable_zone/include/linux/mempolicy.h      
2007-01-07 05:45:51.000000000 +0000
+++ linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/include/linux/mempolicy.h   
2007-01-25 17:34:15.000000000 +0000
@@ -159,7 +159,7 @@ extern void mpol_fix_fork_child_flag(str
 
 extern struct mempolicy default_policy;
 extern struct zonelist *huge_zonelist(struct vm_area_struct *vma,
-               unsigned long addr);
+               unsigned long addr, gfp_t gfp_flags);
 extern unsigned slab_node(struct mempolicy *policy);
 
 extern enum zone_type policy_zone;
@@ -256,9 +256,9 @@ static inline void mpol_fix_fork_child_f
 #define set_cpuset_being_rebound(x) do {} while (0)
 
 static inline struct zonelist *huge_zonelist(struct vm_area_struct *vma,
-               unsigned long addr)
+               unsigned long addr, gfp_t gfp_flags)
 {
-       return NODE_DATA(0)->node_zonelists + gfp_zone(GFP_HIGHUSER);
+       return NODE_DATA(0)->node_zonelists + gfp_zone(gfp_flags);
 }
 
 static inline int do_migrate_pages(struct mm_struct *mm,
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.20-rc4-mm1-002_create_movable_zone/include/linux/sysctl.h 
linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/include/linux/sysctl.h
--- linux-2.6.20-rc4-mm1-002_create_movable_zone/include/linux/sysctl.h 
2007-01-07 05:45:51.000000000 +0000
+++ linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/include/linux/sysctl.h      
2007-01-25 17:34:15.000000000 +0000
@@ -202,6 +202,7 @@ enum
        VM_PANIC_ON_OOM=33,     /* panic at out-of-memory */
        VM_VDSO_ENABLED=34,     /* map VDSO into new processes? */
        VM_MIN_SLAB=35,          /* Percent pages ignored by zone reclaim */
+       VM_HUGETLB_TREAT_MOVABLE=36, /* Allocate hugepages from ZONE_MOVABLE */
 };
 
 
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.20-rc4-mm1-002_create_movable_zone/kernel/sysctl.c 
linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/kernel/sysctl.c
--- linux-2.6.20-rc4-mm1-002_create_movable_zone/kernel/sysctl.c        
2007-01-17 17:08:38.000000000 +0000
+++ linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/kernel/sysctl.c     
2007-01-25 17:34:15.000000000 +0000
@@ -919,6 +919,14 @@ static ctl_table vm_table[] = {
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,
         },
+        {
+               .ctl_name       = VM_HUGETLB_TREAT_MOVABLE,
+               .procname       = "hugepages_treat_as_movable",
+               .data           = &hugepages_treat_as_movable,
+               .maxlen         = sizeof(int),
+               .mode           = 0644,
+               .proc_handler   = &hugetlb_treat_movable_handler,
+       },
 #endif
        {
                .ctl_name       = VM_LOWMEM_RESERVE_RATIO,
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.20-rc4-mm1-002_create_movable_zone/mm/hugetlb.c 
linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/mm/hugetlb.c
--- linux-2.6.20-rc4-mm1-002_create_movable_zone/mm/hugetlb.c   2007-01-07 
05:45:51.000000000 +0000
+++ linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/mm/hugetlb.c        
2007-01-25 17:34:15.000000000 +0000
@@ -27,6 +27,9 @@ unsigned long max_huge_pages;
 static struct list_head hugepage_freelists[MAX_NUMNODES];
 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
 static unsigned int free_huge_pages_node[MAX_NUMNODES];
+gfp_t htlb_alloc_mask = GFP_HIGHUSER;
+unsigned long hugepages_treat_as_movable;
+
 /*
  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  */
@@ -68,12 +71,13 @@ static struct page *dequeue_huge_page(st
 {
        int nid = numa_node_id();
        struct page *page = NULL;
-       struct zonelist *zonelist = huge_zonelist(vma, address);
+       struct zonelist *zonelist = huge_zonelist(vma, address,
+                                               htlb_alloc_mask);
        struct zone **z;
 
        for (z = zonelist->zones; *z; z++) {
                nid = zone_to_nid(*z);
-               if (cpuset_zone_allowed_softwall(*z, GFP_HIGHUSER) &&
+               if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
                    !list_empty(&hugepage_freelists[nid]))
                        break;
        }
@@ -103,7 +107,7 @@ static int alloc_fresh_huge_page(void)
 {
        static int nid = 0;
        struct page *page;
-       page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
+       page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
                                        HUGETLB_PAGE_ORDER);
        nid = next_node(nid, node_online_map);
        if (nid == MAX_NUMNODES)
@@ -243,6 +247,19 @@ int hugetlb_sysctl_handler(struct ctl_ta
        max_huge_pages = set_max_huge_pages(max_huge_pages);
        return 0;
 }
+
+int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
+                       struct file *file, void __user *buffer,
+                       size_t *length, loff_t *ppos)
+{
+       proc_dointvec(table, write, file, buffer, length, ppos);
+       if (hugepages_treat_as_movable)
+               htlb_alloc_mask = GFP_HIGH_MOVABLE;
+       else
+               htlb_alloc_mask = GFP_HIGHUSER;
+       return 0;
+}
+
 #endif /* CONFIG_SYSCTL */
 
 int hugetlb_report_meminfo(char *buf)
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.20-rc4-mm1-002_create_movable_zone/mm/mempolicy.c 
linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/mm/mempolicy.c
--- linux-2.6.20-rc4-mm1-002_create_movable_zone/mm/mempolicy.c 2007-01-25 
17:30:30.000000000 +0000
+++ linux-2.6.20-rc4-mm1-003_mark_hugepages_movable/mm/mempolicy.c      
2007-01-25 17:34:15.000000000 +0000
@@ -1203,7 +1203,8 @@ static inline unsigned interleave_nid(st
 
 #ifdef CONFIG_HUGETLBFS
 /* Return a zonelist suitable for a huge page allocation. */
-struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr)
+struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr,
+                                                       gfp_t gfp_flags)
 {
        struct mempolicy *pol = get_vma_policy(current, vma, addr);
 
@@ -1211,7 +1212,7 @@ struct zonelist *huge_zonelist(struct vm
                unsigned nid;
 
                nid = interleave_nid(pol, vma, addr, HPAGE_SHIFT);
-               return NODE_DATA(nid)->node_zonelists + gfp_zone(GFP_HIGHUSER);
+               return NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_flags);
        }
        return zonelist_policy(GFP_HIGHUSER, pol);
 }
-
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