Re: [PATCH 02/10] hugetlb: add allocate function for hugepagemigration

[Naoya Horiguchi]

Hi,

Thank you for your review.

On Mon, Sep 20, 2010 at 11:59:16AM +0100, Mel Gorman wrote:
> On Wed, Sep 08, 2010 at 10:19:33AM +0900, Naoya Horiguchi wrote:
...
> > @@ -770,11 +776,10 @@ static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
> >  	return ret;
> >  }
> >  
> > -static struct page *alloc_buddy_huge_page(struct hstate *h,
> > -			struct vm_area_struct *vma, unsigned long address)
> > +static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
> >  {
> >  	struct page *page;
> > -	unsigned int nid;
> > +	unsigned int r_nid;
> >  
> 
> Why the rename, just to avoid changing the value of a function parameter?

I think it's better that a simple name is given to function parameter
than to internal variable, because the former is paid more attention
from other developers than the latter is.

> >  	if (h->order >= MAX_ORDER)
> >  		return NULL;
> > @@ -812,9 +817,14 @@ static struct page *alloc_buddy_huge_page(struct hstate *h,
> >  	}
> >  	spin_unlock(&hugetlb_lock);
> >  
> > -	page = alloc_pages(htlb_alloc_mask|__GFP_COMP|
> > -					__GFP_REPEAT|__GFP_NOWARN,
> > -					huge_page_order(h));
> > +	if (nid == NUMA_NO_NODE)
> > +		page = alloc_pages(htlb_alloc_mask|__GFP_COMP|
> > +				   __GFP_REPEAT|__GFP_NOWARN,
> > +				   huge_page_order(h));
> > +	else
> > +		page = alloc_pages_exact_node(nid,
> > +			htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|
> > +			__GFP_REPEAT|__GFP_NOWARN, huge_page_order(h));
> >  
> 
> Why not just call alloc_pages_node()?

Ah, we can bring together these two allocate functions.
I'll do it.

Here is a revised patch.

Thanks,
Naoya Horiguchi
---
Date: Wed, 22 Sep 2010 13:18:54 +0900
Subject: [PATCH 02/10] hugetlb: add allocate function for hugepage migration

We can't use existing hugepage allocation functions to allocate hugepage
for page migration, because page migration can happen asynchronously with
the running processes and page migration users should call the allocation
function with physical addresses (not virtual addresses) as arguments.

ChangeLog since v3:
- unify alloc_buddy_huge_page() and alloc_buddy_huge_page_node()
- bring together branched allocate functions

ChangeLog since v2:
- remove unnecessary get/put_mems_allowed() (thanks to David Rientjes)

ChangeLog since v1:
- add comment on top of alloc_huge_page_no_vma()

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
---
 include/linux/hugetlb.h |    3 ++
 mm/hugetlb.c            |   70 +++++++++++++++++++++++++++++++---------------
 2 files changed, 50 insertions(+), 23 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index f479700..0b73c53 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -228,6 +228,8 @@ struct huge_bootmem_page {
 	struct hstate *hstate;
 };
 
+struct page *alloc_huge_page_node(struct hstate *h, int nid);
+
 /* arch callback */
 int __init alloc_bootmem_huge_page(struct hstate *h);
 
@@ -303,6 +305,7 @@ static inline struct hstate *page_hstate(struct page *page)
 
 #else
 struct hstate {};
+#define alloc_huge_page_node(h, nid) NULL
 #define alloc_bootmem_huge_page(h) NULL
 #define hstate_file(f) NULL
 #define hstate_vma(v) NULL
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6871b41..cb32a32 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -466,11 +466,23 @@ static void enqueue_huge_page(struct hstate *h, struct page *page)
 	h->free_huge_pages_node[nid]++;
 }
 
+static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
+{
+	struct page *page;
+
+	if (list_empty(&h->hugepage_freelists[nid]))
+		return NULL;
+	page = list_entry(h->hugepage_freelists[nid].next, struct page, lru);
+	list_del(&page->lru);
+	h->free_huge_pages--;
+	h->free_huge_pages_node[nid]--;
+	return page;
+}
+
 static struct page *dequeue_huge_page_vma(struct hstate *h,
 				struct vm_area_struct *vma,
 				unsigned long address, int avoid_reserve)
 {
-	int nid;
 	struct page *page = NULL;
 	struct mempolicy *mpol;
 	nodemask_t *nodemask;
@@ -496,19 +508,13 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 						MAX_NR_ZONES - 1, nodemask) {
-		nid = zone_to_nid(zone);
-		if (cpuset_zone_allowed_softwall(zone, htlb_alloc_mask) &&
-		    !list_empty(&h->hugepage_freelists[nid])) {
-			page = list_entry(h->hugepage_freelists[nid].next,
-					  struct page, lru);
-			list_del(&page->lru);
-			h->free_huge_pages--;
-			h->free_huge_pages_node[nid]--;
-
-			if (!avoid_reserve)
-				decrement_hugepage_resv_vma(h, vma);
-
-			break;
+		if (cpuset_zone_allowed_softwall(zone, htlb_alloc_mask)) {
+			page = dequeue_huge_page_node(h, zone_to_nid(zone));
+			if (page) {
+				if (!avoid_reserve)
+					decrement_hugepage_resv_vma(h, vma);
+				break;
+			}
 		}
 	}
 err:
@@ -770,11 +776,10 @@ static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
 	return ret;
 }
 
-static struct page *alloc_buddy_huge_page(struct hstate *h,
-			struct vm_area_struct *vma, unsigned long address)
+static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
 {
 	struct page *page;
-	unsigned int nid;
+	unsigned int r_nid;
 
 	if (h->order >= MAX_ORDER)
 		return NULL;
@@ -812,7 +817,7 @@ static struct page *alloc_buddy_huge_page(struct hstate *h,
 	}
 	spin_unlock(&hugetlb_lock);
 
-	page = alloc_pages(htlb_alloc_mask|__GFP_COMP|
+	page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|
 					__GFP_REPEAT|__GFP_NOWARN,
 					huge_page_order(h));
 
@@ -829,13 +834,13 @@ static struct page *alloc_buddy_huge_page(struct hstate *h,
 		 */
 		put_page_testzero(page);
 		VM_BUG_ON(page_count(page));
-		nid = page_to_nid(page);
+		r_nid = page_to_nid(page);
 		set_compound_page_dtor(page, free_huge_page);
 		/*
 		 * We incremented the global counters already
 		 */
-		h->nr_huge_pages_node[nid]++;
-		h->surplus_huge_pages_node[nid]++;
+		h->nr_huge_pages_node[r_nid]++;
+		h->surplus_huge_pages_node[r_nid]++;
 		__count_vm_event(HTLB_BUDDY_PGALLOC);
 	} else {
 		h->nr_huge_pages--;
@@ -848,6 +853,25 @@ static struct page *alloc_buddy_huge_page(struct hstate *h,
 }
 
 /*
+ * This allocation function is useful in the context where vma is irrelevant.
+ * E.g. soft-offlining uses this function because it only cares physical
+ * address of error page.
+ */
+struct page *alloc_huge_page_node(struct hstate *h, int nid)
+{
+	struct page *page;
+
+	spin_lock(&hugetlb_lock);
+	page = dequeue_huge_page_node(h, nid);
+	spin_unlock(&hugetlb_lock);
+
+	if (!page)
+		page = alloc_buddy_huge_page(h, nid);
+
+	return page;
+}
+
+/*
  * Increase the hugetlb pool such that it can accomodate a reservation
  * of size 'delta'.
  */
@@ -871,7 +895,7 @@ static int gather_surplus_pages(struct hstate *h, int delta)
 retry:
 	spin_unlock(&hugetlb_lock);
 	for (i = 0; i < needed; i++) {
-		page = alloc_buddy_huge_page(h, NULL, 0);
+		page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
 		if (!page) {
 			/*
 			 * We were not able to allocate enough pages to
@@ -1052,7 +1076,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 	spin_unlock(&hugetlb_lock);
 
 	if (!page) {
-		page = alloc_buddy_huge_page(h, vma, addr);
+		page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
 		if (!page) {
 			hugetlb_put_quota(inode->i_mapping, chg);
 			return ERR_PTR(-VM_FAULT_SIGBUS);
-- 
1.7.2.3

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