[Changelog at the bottom]
Introduction
------------
The HugeTLB subsystem uses the buddy allocator to allocate hugepages during
runtime. This means that hugepages allocation during runtime is limited to
MAX_ORDER order. For archs supporting gigantic pages (that is, page sizes
greater than MAX_ORDER), this in turn means that those pages can't be
allocated at runtime.
HugeTLB supports gigantic page allocation during boottime, via the boot
allocator. To this end the kernel provides the command-line options
hugepagesz= and hugepages=, which can be used to instruct the kernel to
allocate N gigantic pages during boot.
For example, x86_64 supports 2M and 1G hugepages, but only 2M hugepages can
be allocated and freed at runtime. If one wants to allocate 1G gigantic pages,
this has to be done at boot via the hugepagesz= and hugepages= command-line
options.
Now, gigantic page allocation at boottime has two serious problems:
1. Boottime allocation is not NUMA aware. On a NUMA machine the kernel
evenly distributes boottime allocated hugepages among nodes.
For example, suppose you have a four-node NUMA machine and want
to allocate four 1G gigantic pages at boottime. The kernel will
allocate one gigantic page per node.
On the other hand, we do have users who want to be able to specify
which NUMA node gigantic pages should allocated from. So that they
can place virtual machines on a specific NUMA node.
2. Gigantic pages allocated at boottime can't be freed
At this point it's important to observe that regular hugepages allocated
at runtime don't have those problems. This is so because HugeTLB interface
for runtime allocation in sysfs supports NUMA and runtime allocated pages
can be freed just fine via the buddy allocator.
This series adds support for allocating gigantic pages at runtime. It does
so by allocating gigantic pages via CMA instead of the buddy allocator.
Releasing gigantic pages is also supported via CMA. As this series builds
on top of the existing HugeTLB interface, it makes gigantic page allocation
and releasing just like regular sized hugepages. This also means that NUMA
support just works.
For example, to allocate two 1G gigantic pages on node 1, one can do:
# echo 2 > \
/sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
And, to release all gigantic pages on the same node:
# echo 0 > \
/sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
Please, refer to patch 5/5 for full technical details.
Finally, please note that this series is a follow up for a previous series
that tried to extend the command-line options set to be NUMA aware:
http://marc.info/?l=linux-mm&m=139593335312191&w=2
During the discussion of that series it was agreed that having runtime
allocation support for gigantic pages was a better solution.
Changelog
---------
v2
- Rewrote allocation loop to avoid scanning useless PFNs [Yasuaki]
- Dropped incomplete multi-arch support [Naoya]
- Added patch to drop __init from prep_compound_gigantic_page()
- Restricted the feature to x86_64 (more details in patch 5/5)
- Added reviewed-bys plus minor changelog changes
Luiz Capitulino (5):
hugetlb: prep_compound_gigantic_page(): drop __init marker
hugetlb: add hstate_is_gigantic()
hugetlb: update_and_free_page(): don't clear PG_reserved bit
hugetlb: move helpers up in the file
hugetlb: add support for gigantic page allocation at runtime
include/linux/hugetlb.h | 5 +
mm/hugetlb.c | 328 ++++++++++++++++++++++++++++++++++--------------
2 files changed, 237 insertions(+), 96 deletions(-)
--
1.8.1.4
This function is going to be used by non-init code in a future
commit.
Signed-off-by: Luiz Capitulino <[email protected]>
---
mm/hugetlb.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7c02b9d..319db28 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -689,8 +689,7 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
put_page(page); /* free it into the hugepage allocator */
}
-static void __init prep_compound_gigantic_page(struct page *page,
- unsigned long order)
+static void prep_compound_gigantic_page(struct page *page, unsigned long order)
{
int i;
int nr_pages = 1 << order;
--
1.8.1.4
HugeTLB is limited to allocating hugepages whose size are less than
MAX_ORDER order. This is so because HugeTLB allocates hugepages via
the buddy allocator. Gigantic pages (that is, pages whose size is
greater than MAX_ORDER order) have to be allocated at boottime.
However, boottime allocation has at least two serious problems. First,
it doesn't support NUMA and second, gigantic pages allocated at
boottime can't be freed.
This commit solves both issues by adding support for allocating gigantic
pages during runtime. It works just like regular sized hugepages,
meaning that the interface in sysfs is the same, it supports NUMA,
and gigantic pages can be freed.
For example, on x86_64 gigantic pages are 1GB big. To allocate two 1G
gigantic pages on node 1, one can do:
# echo 2 > \
/sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
And to free them all:
# echo 0 > \
/sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
The one problem with gigantic page allocation at runtime is that it
can't be serviced by the buddy allocator. To overcome that problem, this
commit scans all zones from a node looking for a large enough contiguous
region. When one is found, it's allocated by using CMA, that is, we call
alloc_contig_range() to do the actual allocation. For example, on x86_64
we scan all zones looking for a 1GB contiguous region. When one is found,
it's allocated by alloc_contig_range().
One expected issue with that approach is that such gigantic contiguous
regions tend to vanish as runtime goes by. The best way to avoid this for
now is to make gigantic page allocations very early during system boot, say
from a init script. Other possible optimization include using compaction,
which is supported by CMA but is not explicitly used by this commit.
It's also important to note the following:
1. Gigantic pages allocated at boottime by the hugepages= command-line
option can be freed at runtime just fine
2. This commit adds support for gigantic pages only to x86_64. The
reason is that I don't have access to nor experience with other archs.
The code is arch indepedent though, so it should be simple to add
support to different archs
3. I didn't add support for hugepage overcommit, that is allocating
a gigantic page on demand when
/proc/sys/vm/nr_overcommit_hugepages > 0. The reason is that I don't
think it's reasonable to do the hard and long work required for
allocating a gigantic page at fault time. But it should be simple
to add this if wanted
Signed-off-by: Luiz Capitulino <[email protected]>
---
mm/hugetlb.c | 158 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 147 insertions(+), 11 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9dded98..2258045 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -679,11 +679,141 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
((node = hstate_next_node_to_free(hs, mask)) || 1); \
nr_nodes--)
+#if defined(CONFIG_CMA) && defined(CONFIG_X86_64)
+static void destroy_compound_gigantic_page(struct page *page,
+ unsigned long order)
+{
+ int i;
+ int nr_pages = 1 << order;
+ struct page *p = page + 1;
+
+ for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
+ __ClearPageTail(p);
+ set_page_refcounted(p);
+ p->first_page = NULL;
+ }
+
+ set_compound_order(page, 0);
+ __ClearPageHead(page);
+}
+
+static void free_gigantic_page(struct page *page, unsigned order)
+{
+ free_contig_range(page_to_pfn(page), 1 << order);
+}
+
+static int __alloc_gigantic_page(unsigned long start_pfn, unsigned long count)
+{
+ unsigned long end_pfn = start_pfn + count;
+ return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
+}
+
+static bool pfn_range_valid_gigantic(unsigned long start_pfn,
+ unsigned long nr_pages)
+{
+ unsigned long i, end_pfn = start_pfn + nr_pages;
+ struct page *page;
+
+ for (i = start_pfn; i < end_pfn; i++) {
+ if (!pfn_valid(i))
+ return false;
+
+ page = pfn_to_page(i);
+
+ if (PageReserved(page))
+ return false;
+
+ if (page_count(page) > 0)
+ return false;
+
+ if (PageHuge(page))
+ return false;
+ }
+
+ return true;
+}
+
+static struct page *alloc_gigantic_page(int nid, unsigned order)
+{
+ unsigned long nr_pages = 1 << order;
+ unsigned long ret, pfn, flags;
+ struct zone *z;
+
+ z = NODE_DATA(nid)->node_zones;
+ for (; z - NODE_DATA(nid)->node_zones < MAX_NR_ZONES; z++) {
+ spin_lock_irqsave(&z->lock, flags);
+
+ pfn = ALIGN(z->zone_start_pfn, nr_pages);
+ for (; pfn < zone_end_pfn(z); pfn += nr_pages) {
+ if (pfn_range_valid_gigantic(pfn, nr_pages)) {
+ /*
+ * We release the zone lock here because
+ * alloc_contig_range() will also lock the zone
+ * at some point. If there's an allocation
+ * spinning on this lock, it may win the race
+ * and cause alloc_contig_range() to fail...
+ */
+ spin_unlock_irqrestore(&z->lock, flags);
+ ret = __alloc_gigantic_page(pfn, nr_pages);
+ if (!ret)
+ return pfn_to_page(pfn);
+ spin_lock_irqsave(&z->lock, flags);
+ }
+ }
+
+ spin_unlock_irqrestore(&z->lock, flags);
+ }
+
+ return NULL;
+}
+
+static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
+static void prep_compound_gigantic_page(struct page *page, unsigned long order);
+
+static struct page *alloc_fresh_gigantic_page_node(struct hstate *h, int nid)
+{
+ struct page *page;
+
+ page = alloc_gigantic_page(nid, huge_page_order(h));
+ if (page) {
+ prep_compound_gigantic_page(page, huge_page_order(h));
+ prep_new_huge_page(h, page, nid);
+ }
+
+ return page;
+}
+
+static int alloc_fresh_gigantic_page(struct hstate *h,
+ nodemask_t *nodes_allowed)
+{
+ struct page *page = NULL;
+ int nr_nodes, node;
+
+ for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
+ page = alloc_fresh_gigantic_page_node(h, node);
+ if (page)
+ return 1;
+ }
+
+ return 0;
+}
+
+static inline bool gigantic_page_supported(void) { return true; }
+#else
+static inline bool gigantic_page_supported(void) { return false; }
+static inline void free_gigantic_page(struct page *page, unsigned order) { }
+static inline void destroy_compound_gigantic_page(struct page *page,
+ unsigned long order) { }
+static inline int alloc_fresh_gigantic_page(struct hstate *h,
+ nodemask_t *nodes_allowed) { return 0; }
+#endif
+
static void update_and_free_page(struct hstate *h, struct page *page)
{
int i;
- VM_BUG_ON(hstate_is_gigantic(h));
+ if (hstate_is_gigantic(h) && !gigantic_page_supported())
+ return;
h->nr_huge_pages--;
h->nr_huge_pages_node[page_to_nid(page)]--;
@@ -697,8 +827,13 @@ static void update_and_free_page(struct hstate *h, struct page *page)
VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
set_compound_page_dtor(page, NULL);
set_page_refcounted(page);
- arch_release_hugepage(page);
- __free_pages(page, huge_page_order(h));
+ if (hstate_is_gigantic(h)) {
+ destroy_compound_gigantic_page(page, huge_page_order(h));
+ free_gigantic_page(page, huge_page_order(h));
+ } else {
+ arch_release_hugepage(page);
+ __free_pages(page, huge_page_order(h));
+ }
}
struct hstate *size_to_hstate(unsigned long size)
@@ -737,7 +872,7 @@ static void free_huge_page(struct page *page)
if (restore_reserve)
h->resv_huge_pages++;
- if (h->surplus_huge_pages_node[nid] && !hstate_is_gigantic(h)) {
+ if (h->surplus_huge_pages_node[nid]) {
/* remove the page from active list */
list_del(&page->lru);
update_and_free_page(h, page);
@@ -841,9 +976,6 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
{
struct page *page;
- if (hstate_is_gigantic(h))
- return NULL;
-
page = alloc_pages_exact_node(nid,
htlb_alloc_mask(h)|__GFP_COMP|__GFP_THISNODE|
__GFP_REPEAT|__GFP_NOWARN,
@@ -1477,7 +1609,7 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
{
unsigned long min_count, ret;
- if (hstate_is_gigantic(h))
+ if (hstate_is_gigantic(h) && !gigantic_page_supported())
return h->max_huge_pages;
/*
@@ -1504,7 +1636,11 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
* and reducing the surplus.
*/
spin_unlock(&hugetlb_lock);
- ret = alloc_fresh_huge_page(h, nodes_allowed);
+ if (hstate_is_gigantic(h)) {
+ ret = alloc_fresh_gigantic_page(h, nodes_allowed);
+ } else {
+ ret = alloc_fresh_huge_page(h, nodes_allowed);
+ }
spin_lock(&hugetlb_lock);
if (!ret)
goto out;
@@ -1603,7 +1739,7 @@ static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
goto out;
h = kobj_to_hstate(kobj, &nid);
- if (hstate_is_gigantic(h)) {
+ if (hstate_is_gigantic(h) && !gigantic_page_supported()) {
err = -EINVAL;
goto out;
}
@@ -2111,7 +2247,7 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
tmp = h->max_huge_pages;
- if (write && hstate_is_gigantic(h))
+ if (write && hstate_is_gigantic(h) && !gigantic_page_supported())
return -EINVAL;
table->data = &tmp;
--
1.8.1.4
Hugepages pages never get the PG_reserved bit set, so don't clear it. But
add a warning just in case.
Signed-off-by: Luiz Capitulino <[email protected]>
Reviewed-by: Andrea Arcangeli <[email protected]>
Reviewed-by: Naoya Horiguchi <[email protected]>
Reviewed-by: Yasuaki Ishimatsu <[email protected]>
---
mm/hugetlb.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8674eda..c295bba 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -617,8 +617,9 @@ static void update_and_free_page(struct hstate *h, struct page *page)
for (i = 0; i < pages_per_huge_page(h); i++) {
page[i].flags &= ~(1 << PG_locked | 1 << PG_error |
1 << PG_referenced | 1 << PG_dirty |
- 1 << PG_active | 1 << PG_reserved |
- 1 << PG_private | 1 << PG_writeback);
+ 1 << PG_active | 1 << PG_private |
+ 1 << PG_writeback);
+ WARN_ON(PageReserved(&page[i]));
}
VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
set_compound_page_dtor(page, NULL);
--
1.8.1.4
Next commit will add new code which will want to call
for_each_node_mask_to_alloc() macro. Move it, its buddy
for_each_node_mask_to_free() and their dependencies up in the file so
the new code can use them. This is just code movement, no logic change.
Signed-off-by: Luiz Capitulino <[email protected]>
Reviewed-by: Andrea Arcangeli <[email protected]>
Reviewed-by: Naoya Horiguchi <[email protected]>
Reviewed-by: Yasuaki Ishimatsu <[email protected]>
---
mm/hugetlb.c | 146 +++++++++++++++++++++++++++++------------------------------
1 file changed, 73 insertions(+), 73 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c295bba..9dded98 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -606,6 +606,79 @@ err:
return NULL;
}
+/*
+ * common helper functions for hstate_next_node_to_{alloc|free}.
+ * We may have allocated or freed a huge page based on a different
+ * nodes_allowed previously, so h->next_node_to_{alloc|free} might
+ * be outside of *nodes_allowed. Ensure that we use an allowed
+ * node for alloc or free.
+ */
+static int next_node_allowed(int nid, nodemask_t *nodes_allowed)
+{
+ nid = next_node(nid, *nodes_allowed);
+ if (nid == MAX_NUMNODES)
+ nid = first_node(*nodes_allowed);
+ VM_BUG_ON(nid >= MAX_NUMNODES);
+
+ return nid;
+}
+
+static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
+{
+ if (!node_isset(nid, *nodes_allowed))
+ nid = next_node_allowed(nid, nodes_allowed);
+ return nid;
+}
+
+/*
+ * returns the previously saved node ["this node"] from which to
+ * allocate a persistent huge page for the pool and advance the
+ * next node from which to allocate, handling wrap at end of node
+ * mask.
+ */
+static int hstate_next_node_to_alloc(struct hstate *h,
+ nodemask_t *nodes_allowed)
+{
+ int nid;
+
+ VM_BUG_ON(!nodes_allowed);
+
+ nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
+ h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
+
+ return nid;
+}
+
+/*
+ * helper for free_pool_huge_page() - return the previously saved
+ * node ["this node"] from which to free a huge page. Advance the
+ * next node id whether or not we find a free huge page to free so
+ * that the next attempt to free addresses the next node.
+ */
+static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
+{
+ int nid;
+
+ VM_BUG_ON(!nodes_allowed);
+
+ nid = get_valid_node_allowed(h->next_nid_to_free, nodes_allowed);
+ h->next_nid_to_free = next_node_allowed(nid, nodes_allowed);
+
+ return nid;
+}
+
+#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask) \
+ for (nr_nodes = nodes_weight(*mask); \
+ nr_nodes > 0 && \
+ ((node = hstate_next_node_to_alloc(hs, mask)) || 1); \
+ nr_nodes--)
+
+#define for_each_node_mask_to_free(hs, nr_nodes, node, mask) \
+ for (nr_nodes = nodes_weight(*mask); \
+ nr_nodes > 0 && \
+ ((node = hstate_next_node_to_free(hs, mask)) || 1); \
+ nr_nodes--)
+
static void update_and_free_page(struct hstate *h, struct page *page)
{
int i;
@@ -786,79 +859,6 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
return page;
}
-/*
- * common helper functions for hstate_next_node_to_{alloc|free}.
- * We may have allocated or freed a huge page based on a different
- * nodes_allowed previously, so h->next_node_to_{alloc|free} might
- * be outside of *nodes_allowed. Ensure that we use an allowed
- * node for alloc or free.
- */
-static int next_node_allowed(int nid, nodemask_t *nodes_allowed)
-{
- nid = next_node(nid, *nodes_allowed);
- if (nid == MAX_NUMNODES)
- nid = first_node(*nodes_allowed);
- VM_BUG_ON(nid >= MAX_NUMNODES);
-
- return nid;
-}
-
-static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
-{
- if (!node_isset(nid, *nodes_allowed))
- nid = next_node_allowed(nid, nodes_allowed);
- return nid;
-}
-
-/*
- * returns the previously saved node ["this node"] from which to
- * allocate a persistent huge page for the pool and advance the
- * next node from which to allocate, handling wrap at end of node
- * mask.
- */
-static int hstate_next_node_to_alloc(struct hstate *h,
- nodemask_t *nodes_allowed)
-{
- int nid;
-
- VM_BUG_ON(!nodes_allowed);
-
- nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
- h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
-
- return nid;
-}
-
-/*
- * helper for free_pool_huge_page() - return the previously saved
- * node ["this node"] from which to free a huge page. Advance the
- * next node id whether or not we find a free huge page to free so
- * that the next attempt to free addresses the next node.
- */
-static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
-{
- int nid;
-
- VM_BUG_ON(!nodes_allowed);
-
- nid = get_valid_node_allowed(h->next_nid_to_free, nodes_allowed);
- h->next_nid_to_free = next_node_allowed(nid, nodes_allowed);
-
- return nid;
-}
-
-#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask) \
- for (nr_nodes = nodes_weight(*mask); \
- nr_nodes > 0 && \
- ((node = hstate_next_node_to_alloc(hs, mask)) || 1); \
- nr_nodes--)
-
-#define for_each_node_mask_to_free(hs, nr_nodes, node, mask) \
- for (nr_nodes = nodes_weight(*mask); \
- nr_nodes > 0 && \
- ((node = hstate_next_node_to_free(hs, mask)) || 1); \
- nr_nodes--)
-
static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
{
struct page *page;
--
1.8.1.4
Signed-off-by: Luiz Capitulino <[email protected]>
Reviewed-by: Andrea Arcangeli <[email protected]>
Reviewed-by: Naoya Horiguchi <[email protected]>
Reviewed-by: Yasuaki Ishimatsu <[email protected]>
---
include/linux/hugetlb.h | 5 +++++
mm/hugetlb.c | 28 ++++++++++++++--------------
2 files changed, 19 insertions(+), 14 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 5b337cf..62a8b88 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -343,6 +343,11 @@ static inline unsigned huge_page_shift(struct hstate *h)
return h->order + PAGE_SHIFT;
}
+static inline bool hstate_is_gigantic(struct hstate *h)
+{
+ return huge_page_order(h) >= MAX_ORDER;
+}
+
static inline unsigned int pages_per_huge_page(struct hstate *h)
{
return 1 << h->order;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 319db28..8674eda 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -610,7 +610,7 @@ static void update_and_free_page(struct hstate *h, struct page *page)
{
int i;
- VM_BUG_ON(h->order >= MAX_ORDER);
+ VM_BUG_ON(hstate_is_gigantic(h));
h->nr_huge_pages--;
h->nr_huge_pages_node[page_to_nid(page)]--;
@@ -663,7 +663,7 @@ static void free_huge_page(struct page *page)
if (restore_reserve)
h->resv_huge_pages++;
- if (h->surplus_huge_pages_node[nid] && huge_page_order(h) < MAX_ORDER) {
+ if (h->surplus_huge_pages_node[nid] && !hstate_is_gigantic(h)) {
/* remove the page from active list */
list_del(&page->lru);
update_and_free_page(h, page);
@@ -767,7 +767,7 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
{
struct page *page;
- if (h->order >= MAX_ORDER)
+ if (hstate_is_gigantic(h))
return NULL;
page = alloc_pages_exact_node(nid,
@@ -961,7 +961,7 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
struct page *page;
unsigned int r_nid;
- if (h->order >= MAX_ORDER)
+ if (hstate_is_gigantic(h))
return NULL;
/*
@@ -1154,7 +1154,7 @@ static void return_unused_surplus_pages(struct hstate *h,
h->resv_huge_pages -= unused_resv_pages;
/* Cannot return gigantic pages currently */
- if (h->order >= MAX_ORDER)
+ if (hstate_is_gigantic(h))
return;
nr_pages = min(unused_resv_pages, h->surplus_huge_pages);
@@ -1353,7 +1353,7 @@ static void __init gather_bootmem_prealloc(void)
* fix confusing memory reports from free(1) and another
* side-effects, like CommitLimit going negative.
*/
- if (h->order > (MAX_ORDER - 1))
+ if (hstate_is_gigantic(h))
adjust_managed_page_count(page, 1 << h->order);
}
}
@@ -1363,7 +1363,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
unsigned long i;
for (i = 0; i < h->max_huge_pages; ++i) {
- if (h->order >= MAX_ORDER) {
+ if (hstate_is_gigantic(h)) {
if (!alloc_bootmem_huge_page(h))
break;
} else if (!alloc_fresh_huge_page(h,
@@ -1379,7 +1379,7 @@ static void __init hugetlb_init_hstates(void)
for_each_hstate(h) {
/* oversize hugepages were init'ed in early boot */
- if (h->order < MAX_ORDER)
+ if (!hstate_is_gigantic(h))
hugetlb_hstate_alloc_pages(h);
}
}
@@ -1413,7 +1413,7 @@ static void try_to_free_low(struct hstate *h, unsigned long count,
{
int i;
- if (h->order >= MAX_ORDER)
+ if (hstate_is_gigantic(h))
return;
for_each_node_mask(i, *nodes_allowed) {
@@ -1476,7 +1476,7 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
{
unsigned long min_count, ret;
- if (h->order >= MAX_ORDER)
+ if (hstate_is_gigantic(h))
return h->max_huge_pages;
/*
@@ -1602,7 +1602,7 @@ static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
goto out;
h = kobj_to_hstate(kobj, &nid);
- if (h->order >= MAX_ORDER) {
+ if (hstate_is_gigantic(h)) {
err = -EINVAL;
goto out;
}
@@ -1685,7 +1685,7 @@ static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj,
unsigned long input;
struct hstate *h = kobj_to_hstate(kobj, NULL);
- if (h->order >= MAX_ORDER)
+ if (hstate_is_gigantic(h))
return -EINVAL;
err = kstrtoul(buf, 10, &input);
@@ -2110,7 +2110,7 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
tmp = h->max_huge_pages;
- if (write && h->order >= MAX_ORDER)
+ if (write && hstate_is_gigantic(h))
return -EINVAL;
table->data = &tmp;
@@ -2163,7 +2163,7 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,
tmp = h->nr_overcommit_huge_pages;
- if (write && h->order >= MAX_ORDER)
+ if (write && hstate_is_gigantic(h))
return -EINVAL;
table->data = &tmp;
--
1.8.1.4
On Tue, 08 Apr 2014 15:51:51 -0400
Naoya Horiguchi <[email protected]> wrote:
> Hi Luiz,
>
> On Tue, Apr 08, 2014 at 03:02:16PM -0400, Luiz Capitulino wrote:
> > This function is going to be used by non-init code in a future
> > commit.
> >
> > Signed-off-by: Luiz Capitulino <[email protected]>
> > ---
> > mm/hugetlb.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 7c02b9d..319db28 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -689,8 +689,7 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
> > put_page(page); /* free it into the hugepage allocator */
> > }
> >
> > -static void __init prep_compound_gigantic_page(struct page *page,
> > - unsigned long order)
> > +static void prep_compound_gigantic_page(struct page *page, unsigned long order)
> > {
> > int i;
> > int nr_pages = 1 << order;
>
> Is __ClearPageReserved() in this function relevant only in boot time
> allocation?
Yes.
> If yes, it might be good to avoid calling it in runtime
> allocation.
The problem is that prep_compound_gigantic_page() is good and used by
both boottime and runtime allocations. Having two functions to do the
same thing seems like overkill, especially because the runtime allocation
code skips reserved pages. So the reserved bit should always be cleared
for runtime allocated gigantic pages.
On Tue, Apr 08, 2014 at 03:02:18PM -0400, Luiz Capitulino wrote:
> Hugepages pages never get the PG_reserved bit set, so don't clear it. But
> add a warning just in case.
I don't think WARN_ON() is needed. PG_reserved will be catched by
free_pages_check().
--
Kirill A. Shutemov
On Tue, 8 Apr 2014 23:51:26 +0300
"Kirill A. Shutemov" <[email protected]> wrote:
> On Tue, Apr 08, 2014 at 03:02:18PM -0400, Luiz Capitulino wrote:
> > Hugepages pages never get the PG_reserved bit set, so don't clear it. But
> > add a warning just in case.
>
> I don't think WARN_ON() is needed. PG_reserved will be catched by
> free_pages_check().
Correct. I'll drop it.
(2014/04/09 4:02), Luiz Capitulino wrote:
> HugeTLB is limited to allocating hugepages whose size are less than
> MAX_ORDER order. This is so because HugeTLB allocates hugepages via
> the buddy allocator. Gigantic pages (that is, pages whose size is
> greater than MAX_ORDER order) have to be allocated at boottime.
>
> However, boottime allocation has at least two serious problems. First,
> it doesn't support NUMA and second, gigantic pages allocated at
> boottime can't be freed.
>
> This commit solves both issues by adding support for allocating gigantic
> pages during runtime. It works just like regular sized hugepages,
> meaning that the interface in sysfs is the same, it supports NUMA,
> and gigantic pages can be freed.
>
> For example, on x86_64 gigantic pages are 1GB big. To allocate two 1G
> gigantic pages on node 1, one can do:
>
> # echo 2 > \
> /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
>
> And to free them all:
>
> # echo 0 > \
> /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
>
> The one problem with gigantic page allocation at runtime is that it
> can't be serviced by the buddy allocator. To overcome that problem, this
> commit scans all zones from a node looking for a large enough contiguous
> region. When one is found, it's allocated by using CMA, that is, we call
> alloc_contig_range() to do the actual allocation. For example, on x86_64
> we scan all zones looking for a 1GB contiguous region. When one is found,
> it's allocated by alloc_contig_range().
>
> One expected issue with that approach is that such gigantic contiguous
> regions tend to vanish as runtime goes by. The best way to avoid this for
> now is to make gigantic page allocations very early during system boot, say
> from a init script. Other possible optimization include using compaction,
> which is supported by CMA but is not explicitly used by this commit.
>
> It's also important to note the following:
>
> 1. Gigantic pages allocated at boottime by the hugepages= command-line
> option can be freed at runtime just fine
>
> 2. This commit adds support for gigantic pages only to x86_64. The
> reason is that I don't have access to nor experience with other archs.
> The code is arch indepedent though, so it should be simple to add
> support to different archs
>
> 3. I didn't add support for hugepage overcommit, that is allocating
> a gigantic page on demand when
> /proc/sys/vm/nr_overcommit_hugepages > 0. The reason is that I don't
> think it's reasonable to do the hard and long work required for
> allocating a gigantic page at fault time. But it should be simple
> to add this if wanted
>
> Signed-off-by: Luiz Capitulino <[email protected]>
> ---
> mm/hugetlb.c | 158 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 147 insertions(+), 11 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 9dded98..2258045 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -679,11 +679,141 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
> ((node = hstate_next_node_to_free(hs, mask)) || 1); \
> nr_nodes--)
>
> +#if defined(CONFIG_CMA) && defined(CONFIG_X86_64)
> +static void destroy_compound_gigantic_page(struct page *page,
> + unsigned long order)
> +{
> + int i;
> + int nr_pages = 1 << order;
> + struct page *p = page + 1;
> +
> + for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
> + __ClearPageTail(p);
> + set_page_refcounted(p);
> + p->first_page = NULL;
> + }
> +
> + set_compound_order(page, 0);
> + __ClearPageHead(page);
> +}
> +
> +static void free_gigantic_page(struct page *page, unsigned order)
> +{
> + free_contig_range(page_to_pfn(page), 1 << order);
> +}
> +
> +static int __alloc_gigantic_page(unsigned long start_pfn, unsigned long count)
> +{
> + unsigned long end_pfn = start_pfn + count;
> + return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
> +}
> +
> +static bool pfn_range_valid_gigantic(unsigned long start_pfn,
> + unsigned long nr_pages)
> +{
> + unsigned long i, end_pfn = start_pfn + nr_pages;
> + struct page *page;
> +
> + for (i = start_pfn; i < end_pfn; i++) {
> + if (!pfn_valid(i))
> + return false;
> +
> + page = pfn_to_page(i);
> +
> + if (PageReserved(page))
> + return false;
> +
> + if (page_count(page) > 0)
> + return false;
> +
> + if (PageHuge(page))
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static struct page *alloc_gigantic_page(int nid, unsigned order)
> +{
> + unsigned long nr_pages = 1 << order;
> + unsigned long ret, pfn, flags;
> + struct zone *z;
> +
> + z = NODE_DATA(nid)->node_zones;
> + for (; z - NODE_DATA(nid)->node_zones < MAX_NR_ZONES; z++) {
> + spin_lock_irqsave(&z->lock, flags);
> +
> + pfn = ALIGN(z->zone_start_pfn, nr_pages);
> + for (; pfn < zone_end_pfn(z); pfn += nr_pages) {
> + if (pfn_range_valid_gigantic(pfn, nr_pages)) {
How about it. It can reduce the indentation level.
if (!pfn_range_valid_gigantic(...))
continue;
And I think following check is necessary:
if (pfn + nr_pages >= zone_end_pfn(z))
break;
Thanks,
Yasuaki Ishimatsu
> + /*
> + * We release the zone lock here because
> + * alloc_contig_range() will also lock the zone
> + * at some point. If there's an allocation
> + * spinning on this lock, it may win the race
> + * and cause alloc_contig_range() to fail...
> + */
> + spin_unlock_irqrestore(&z->lock, flags);
> + ret = __alloc_gigantic_page(pfn, nr_pages);
> + if (!ret)
> + return pfn_to_page(pfn);
> + spin_lock_irqsave(&z->lock, flags);
> + }
> + }
> +
> + spin_unlock_irqrestore(&z->lock, flags);
> + }
> +
> + return NULL;
> +}
> +
> +static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
> +static void prep_compound_gigantic_page(struct page *page, unsigned long order);
> +
> +static struct page *alloc_fresh_gigantic_page_node(struct hstate *h, int nid)
> +{
> + struct page *page;
> +
> + page = alloc_gigantic_page(nid, huge_page_order(h));
> + if (page) {
> + prep_compound_gigantic_page(page, huge_page_order(h));
> + prep_new_huge_page(h, page, nid);
> + }
> +
> + return page;
> +}
> +
> +static int alloc_fresh_gigantic_page(struct hstate *h,
> + nodemask_t *nodes_allowed)
> +{
> + struct page *page = NULL;
> + int nr_nodes, node;
> +
> + for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
> + page = alloc_fresh_gigantic_page_node(h, node);
> + if (page)
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> +static inline bool gigantic_page_supported(void) { return true; }
> +#else
> +static inline bool gigantic_page_supported(void) { return false; }
> +static inline void free_gigantic_page(struct page *page, unsigned order) { }
> +static inline void destroy_compound_gigantic_page(struct page *page,
> + unsigned long order) { }
> +static inline int alloc_fresh_gigantic_page(struct hstate *h,
> + nodemask_t *nodes_allowed) { return 0; }
> +#endif
> +
> static void update_and_free_page(struct hstate *h, struct page *page)
> {
> int i;
>
> - VM_BUG_ON(hstate_is_gigantic(h));
> + if (hstate_is_gigantic(h) && !gigantic_page_supported())
> + return;
>
> h->nr_huge_pages--;
> h->nr_huge_pages_node[page_to_nid(page)]--;
> @@ -697,8 +827,13 @@ static void update_and_free_page(struct hstate *h, struct page *page)
> VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
> set_compound_page_dtor(page, NULL);
> set_page_refcounted(page);
> - arch_release_hugepage(page);
> - __free_pages(page, huge_page_order(h));
> + if (hstate_is_gigantic(h)) {
> + destroy_compound_gigantic_page(page, huge_page_order(h));
> + free_gigantic_page(page, huge_page_order(h));
> + } else {
> + arch_release_hugepage(page);
> + __free_pages(page, huge_page_order(h));
> + }
> }
>
> struct hstate *size_to_hstate(unsigned long size)
> @@ -737,7 +872,7 @@ static void free_huge_page(struct page *page)
> if (restore_reserve)
> h->resv_huge_pages++;
>
> - if (h->surplus_huge_pages_node[nid] && !hstate_is_gigantic(h)) {
> + if (h->surplus_huge_pages_node[nid]) {
> /* remove the page from active list */
> list_del(&page->lru);
> update_and_free_page(h, page);
> @@ -841,9 +976,6 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
> {
> struct page *page;
>
> - if (hstate_is_gigantic(h))
> - return NULL;
> -
> page = alloc_pages_exact_node(nid,
> htlb_alloc_mask(h)|__GFP_COMP|__GFP_THISNODE|
> __GFP_REPEAT|__GFP_NOWARN,
> @@ -1477,7 +1609,7 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
> {
> unsigned long min_count, ret;
>
> - if (hstate_is_gigantic(h))
> + if (hstate_is_gigantic(h) && !gigantic_page_supported())
> return h->max_huge_pages;
>
> /*
> @@ -1504,7 +1636,11 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
> * and reducing the surplus.
> */
> spin_unlock(&hugetlb_lock);
> - ret = alloc_fresh_huge_page(h, nodes_allowed);
> + if (hstate_is_gigantic(h)) {
> + ret = alloc_fresh_gigantic_page(h, nodes_allowed);
> + } else {
> + ret = alloc_fresh_huge_page(h, nodes_allowed);
> + }
> spin_lock(&hugetlb_lock);
> if (!ret)
> goto out;
> @@ -1603,7 +1739,7 @@ static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
> goto out;
>
> h = kobj_to_hstate(kobj, &nid);
> - if (hstate_is_gigantic(h)) {
> + if (hstate_is_gigantic(h) && !gigantic_page_supported()) {
> err = -EINVAL;
> goto out;
> }
> @@ -2111,7 +2247,7 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
>
> tmp = h->max_huge_pages;
>
> - if (write && hstate_is_gigantic(h))
> + if (write && hstate_is_gigantic(h) && !gigantic_page_supported())
> return -EINVAL;
>
> table->data = &tmp;
>
On Wed, 9 Apr 2014 09:42:01 +0900
Yasuaki Ishimatsu <[email protected]> wrote:
> (2014/04/09 4:02), Luiz Capitulino wrote:
> > HugeTLB is limited to allocating hugepages whose size are less than
> > MAX_ORDER order. This is so because HugeTLB allocates hugepages via
> > the buddy allocator. Gigantic pages (that is, pages whose size is
> > greater than MAX_ORDER order) have to be allocated at boottime.
> >
> > However, boottime allocation has at least two serious problems. First,
> > it doesn't support NUMA and second, gigantic pages allocated at
> > boottime can't be freed.
> >
> > This commit solves both issues by adding support for allocating gigantic
> > pages during runtime. It works just like regular sized hugepages,
> > meaning that the interface in sysfs is the same, it supports NUMA,
> > and gigantic pages can be freed.
> >
> > For example, on x86_64 gigantic pages are 1GB big. To allocate two 1G
> > gigantic pages on node 1, one can do:
> >
> > # echo 2 > \
> > /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
> >
> > And to free them all:
> >
> > # echo 0 > \
> > /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
> >
> > The one problem with gigantic page allocation at runtime is that it
> > can't be serviced by the buddy allocator. To overcome that problem, this
> > commit scans all zones from a node looking for a large enough contiguous
> > region. When one is found, it's allocated by using CMA, that is, we call
> > alloc_contig_range() to do the actual allocation. For example, on x86_64
> > we scan all zones looking for a 1GB contiguous region. When one is found,
> > it's allocated by alloc_contig_range().
> >
> > One expected issue with that approach is that such gigantic contiguous
> > regions tend to vanish as runtime goes by. The best way to avoid this for
> > now is to make gigantic page allocations very early during system boot, say
> > from a init script. Other possible optimization include using compaction,
> > which is supported by CMA but is not explicitly used by this commit.
> >
> > It's also important to note the following:
> >
> > 1. Gigantic pages allocated at boottime by the hugepages= command-line
> > option can be freed at runtime just fine
> >
> > 2. This commit adds support for gigantic pages only to x86_64. The
> > reason is that I don't have access to nor experience with other archs.
> > The code is arch indepedent though, so it should be simple to add
> > support to different archs
> >
> > 3. I didn't add support for hugepage overcommit, that is allocating
> > a gigantic page on demand when
> > /proc/sys/vm/nr_overcommit_hugepages > 0. The reason is that I don't
> > think it's reasonable to do the hard and long work required for
> > allocating a gigantic page at fault time. But it should be simple
> > to add this if wanted
> >
> > Signed-off-by: Luiz Capitulino <[email protected]>
> > ---
> > mm/hugetlb.c | 158 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 147 insertions(+), 11 deletions(-)
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 9dded98..2258045 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -679,11 +679,141 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
> > ((node = hstate_next_node_to_free(hs, mask)) || 1); \
> > nr_nodes--)
> >
> > +#if defined(CONFIG_CMA) && defined(CONFIG_X86_64)
> > +static void destroy_compound_gigantic_page(struct page *page,
> > + unsigned long order)
> > +{
> > + int i;
> > + int nr_pages = 1 << order;
> > + struct page *p = page + 1;
> > +
> > + for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
> > + __ClearPageTail(p);
> > + set_page_refcounted(p);
> > + p->first_page = NULL;
> > + }
> > +
> > + set_compound_order(page, 0);
> > + __ClearPageHead(page);
> > +}
> > +
> > +static void free_gigantic_page(struct page *page, unsigned order)
> > +{
> > + free_contig_range(page_to_pfn(page), 1 << order);
> > +}
> > +
> > +static int __alloc_gigantic_page(unsigned long start_pfn, unsigned long count)
> > +{
> > + unsigned long end_pfn = start_pfn + count;
> > + return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
> > +}
> > +
> > +static bool pfn_range_valid_gigantic(unsigned long start_pfn,
> > + unsigned long nr_pages)
> > +{
> > + unsigned long i, end_pfn = start_pfn + nr_pages;
> > + struct page *page;
> > +
> > + for (i = start_pfn; i < end_pfn; i++) {
> > + if (!pfn_valid(i))
> > + return false;
> > +
> > + page = pfn_to_page(i);
> > +
> > + if (PageReserved(page))
> > + return false;
> > +
> > + if (page_count(page) > 0)
> > + return false;
> > +
> > + if (PageHuge(page))
> > + return false;
> > + }
> > +
> > + return true;
> > +}
> > +
> > +static struct page *alloc_gigantic_page(int nid, unsigned order)
> > +{
> > + unsigned long nr_pages = 1 << order;
> > + unsigned long ret, pfn, flags;
> > + struct zone *z;
> > +
> > + z = NODE_DATA(nid)->node_zones;
> > + for (; z - NODE_DATA(nid)->node_zones < MAX_NR_ZONES; z++) {
> > + spin_lock_irqsave(&z->lock, flags);
> > +
> > + pfn = ALIGN(z->zone_start_pfn, nr_pages);
> > + for (; pfn < zone_end_pfn(z); pfn += nr_pages) {
>
> > + if (pfn_range_valid_gigantic(pfn, nr_pages)) {
>
> How about it. It can reduce the indentation level.
> if (!pfn_range_valid_gigantic(...))
> continue;
>
> And I think following check is necessary:
> if (pfn + nr_pages >= zone_end_pfn(z))
> break;
You're right that we have to check if the whole range is within the zone,
but the check above is off-by-one. What about the following:
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 01c0068..b01cdeb 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -734,6 +734,13 @@ static bool pfn_range_valid_gigantic(unsigned long start_pfn,
return true;
}
+static bool zone_spans_last_pfn(const struct zone *zone,
+ unsigned long start_pfn, unsigned long nr_pages)
+{
+ unsigned long last_pfn = start_pfn + nr_pages - 1;
+ return zone_spans_pfn(zone, last_pfn);
+}
+
static struct page *alloc_gigantic_page(int nid, unsigned order)
{
unsigned long nr_pages = 1 << order;
@@ -745,7 +752,7 @@ static struct page *alloc_gigantic_page(int nid, unsigned order)
spin_lock_irqsave(&z->lock, flags);
pfn = ALIGN(z->zone_start_pfn, nr_pages);
- for (; pfn < zone_end_pfn(z); pfn += nr_pages) {
+ while (zone_spans_last_pfn(z, pfn, nr_pages)) {
if (pfn_range_valid_gigantic(pfn, nr_pages)) {
/*
* We release the zone lock here because
@@ -760,6 +767,7 @@ static struct page *alloc_gigantic_page(int nid, unsigned order)
return pfn_to_page(pfn);
spin_lock_irqsave(&z->lock, flags);
}
+ pfn += nr_pages;
}
spin_unlock_irqrestore(&z->lock, flags);
(2014/04/10 2:56), Luiz Capitulino wrote:
> On Wed, 9 Apr 2014 09:42:01 +0900
> Yasuaki Ishimatsu <[email protected]> wrote:
>
>> (2014/04/09 4:02), Luiz Capitulino wrote:
>>> HugeTLB is limited to allocating hugepages whose size are less than
>>> MAX_ORDER order. This is so because HugeTLB allocates hugepages via
>>> the buddy allocator. Gigantic pages (that is, pages whose size is
>>> greater than MAX_ORDER order) have to be allocated at boottime.
>>>
>>> However, boottime allocation has at least two serious problems. First,
>>> it doesn't support NUMA and second, gigantic pages allocated at
>>> boottime can't be freed.
>>>
>>> This commit solves both issues by adding support for allocating gigantic
>>> pages during runtime. It works just like regular sized hugepages,
>>> meaning that the interface in sysfs is the same, it supports NUMA,
>>> and gigantic pages can be freed.
>>>
>>> For example, on x86_64 gigantic pages are 1GB big. To allocate two 1G
>>> gigantic pages on node 1, one can do:
>>>
>>> # echo 2 > \
>>> /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
>>>
>>> And to free them all:
>>>
>>> # echo 0 > \
>>> /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages
>>>
>>> The one problem with gigantic page allocation at runtime is that it
>>> can't be serviced by the buddy allocator. To overcome that problem, this
>>> commit scans all zones from a node looking for a large enough contiguous
>>> region. When one is found, it's allocated by using CMA, that is, we call
>>> alloc_contig_range() to do the actual allocation. For example, on x86_64
>>> we scan all zones looking for a 1GB contiguous region. When one is found,
>>> it's allocated by alloc_contig_range().
>>>
>>> One expected issue with that approach is that such gigantic contiguous
>>> regions tend to vanish as runtime goes by. The best way to avoid this for
>>> now is to make gigantic page allocations very early during system boot, say
>>> from a init script. Other possible optimization include using compaction,
>>> which is supported by CMA but is not explicitly used by this commit.
>>>
>>> It's also important to note the following:
>>>
>>> 1. Gigantic pages allocated at boottime by the hugepages= command-line
>>> option can be freed at runtime just fine
>>>
>>> 2. This commit adds support for gigantic pages only to x86_64. The
>>> reason is that I don't have access to nor experience with other archs.
>>> The code is arch indepedent though, so it should be simple to add
>>> support to different archs
>>>
>>> 3. I didn't add support for hugepage overcommit, that is allocating
>>> a gigantic page on demand when
>>> /proc/sys/vm/nr_overcommit_hugepages > 0. The reason is that I don't
>>> think it's reasonable to do the hard and long work required for
>>> allocating a gigantic page at fault time. But it should be simple
>>> to add this if wanted
>>>
>>> Signed-off-by: Luiz Capitulino <[email protected]>
>>> ---
>>> mm/hugetlb.c | 158 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
>>> 1 file changed, 147 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 9dded98..2258045 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -679,11 +679,141 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
>>> ((node = hstate_next_node_to_free(hs, mask)) || 1); \
>>> nr_nodes--)
>>>
>>> +#if defined(CONFIG_CMA) && defined(CONFIG_X86_64)
>>> +static void destroy_compound_gigantic_page(struct page *page,
>>> + unsigned long order)
>>> +{
>>> + int i;
>>> + int nr_pages = 1 << order;
>>> + struct page *p = page + 1;
>>> +
>>> + for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
>>> + __ClearPageTail(p);
>>> + set_page_refcounted(p);
>>> + p->first_page = NULL;
>>> + }
>>> +
>>> + set_compound_order(page, 0);
>>> + __ClearPageHead(page);
>>> +}
>>> +
>>> +static void free_gigantic_page(struct page *page, unsigned order)
>>> +{
>>> + free_contig_range(page_to_pfn(page), 1 << order);
>>> +}
>>> +
>>> +static int __alloc_gigantic_page(unsigned long start_pfn, unsigned long count)
>>> +{
>>> + unsigned long end_pfn = start_pfn + count;
>>> + return alloc_contig_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
>>> +}
>>> +
>>> +static bool pfn_range_valid_gigantic(unsigned long start_pfn,
>>> + unsigned long nr_pages)
>>> +{
>>> + unsigned long i, end_pfn = start_pfn + nr_pages;
>>> + struct page *page;
>>> +
>>> + for (i = start_pfn; i < end_pfn; i++) {
>>> + if (!pfn_valid(i))
>>> + return false;
>>> +
>>> + page = pfn_to_page(i);
>>> +
>>> + if (PageReserved(page))
>>> + return false;
>>> +
>>> + if (page_count(page) > 0)
>>> + return false;
>>> +
>>> + if (PageHuge(page))
>>> + return false;
>>> + }
>>> +
>>> + return true;
>>> +}
>>> +
>>> +static struct page *alloc_gigantic_page(int nid, unsigned order)
>>> +{
>>> + unsigned long nr_pages = 1 << order;
>>> + unsigned long ret, pfn, flags;
>>> + struct zone *z;
>>> +
>>> + z = NODE_DATA(nid)->node_zones;
>>> + for (; z - NODE_DATA(nid)->node_zones < MAX_NR_ZONES; z++) {
>>> + spin_lock_irqsave(&z->lock, flags);
>>> +
>>> + pfn = ALIGN(z->zone_start_pfn, nr_pages);
>>> + for (; pfn < zone_end_pfn(z); pfn += nr_pages) {
>>
>>> + if (pfn_range_valid_gigantic(pfn, nr_pages)) {
>>
>> How about it. It can reduce the indentation level.
>> if (!pfn_range_valid_gigantic(...))
>> continue;
>>
>> And I think following check is necessary:
>> if (pfn + nr_pages >= zone_end_pfn(z))
>> break;
>
> You're right that we have to check if the whole range is within the zone,
> but the check above is off-by-one. What about the following:
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 01c0068..b01cdeb 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -734,6 +734,13 @@ static bool pfn_range_valid_gigantic(unsigned long start_pfn,
> return true;
> }
>
> +static bool zone_spans_last_pfn(const struct zone *zone,
> + unsigned long start_pfn, unsigned long nr_pages)
> +{
> + unsigned long last_pfn = start_pfn + nr_pages - 1;
> + return zone_spans_pfn(zone, last_pfn);
> +}
> +
> static struct page *alloc_gigantic_page(int nid, unsigned order)
> {
> unsigned long nr_pages = 1 << order;
> @@ -745,7 +752,7 @@ static struct page *alloc_gigantic_page(int nid, unsigned order)
> spin_lock_irqsave(&z->lock, flags);
>
> pfn = ALIGN(z->zone_start_pfn, nr_pages);
> - for (; pfn < zone_end_pfn(z); pfn += nr_pages) {
> + while (zone_spans_last_pfn(z, pfn, nr_pages)) {
> if (pfn_range_valid_gigantic(pfn, nr_pages)) {
> /*
> * We release the zone lock here because
> @@ -760,6 +767,7 @@ static struct page *alloc_gigantic_page(int nid, unsigned order)
> return pfn_to_page(pfn);
> spin_lock_irqsave(&z->lock, flags);
> }
> + pfn += nr_pages;
> }
>
> spin_unlock_irqrestore(&z->lock, flags);
>
Looks good to me.
Thanks,
Yasuaki Ishimatsu