mm, hugetlb: unclutter hugetlb allocation layers
Patch series "mm, hugetlb: allow proper node fallback dequeue".
While working on a hugetlb migration issue addressed in a separate
patchset[1] I have noticed that the hugetlb allocations from the
preallocated pool are quite subotimal.
[1] //lkml.kernel.org/r/20170608074553.22152-1-mhocko@kernel.org
There is no fallback mechanism implemented and no notion of preferred
node. I have tried to work around it but Vlastimil was right to push
back for a more robust solution. It seems that such a solution is to
reuse zonelist approach we use for the page alloctor.
This series has 3 patches. The first one tries to make hugetlb
allocation layers more clear. The second one implements the zonelist
hugetlb pool allocation and introduces a preferred node semantic which
is used by the migration callbacks. The last patch is a clean up.
This patch (of 3):
Hugetlb allocation path for fresh huge pages is unnecessarily complex
and it mixes different interfaces between layers.
__alloc_buddy_huge_page is the central place to perform a new
allocation. It checks for the hugetlb overcommit and then relies on
__hugetlb_alloc_buddy_huge_page to invoke the page allocator. This is
all good except that __alloc_buddy_huge_page pushes vma and address down
the callchain and so __hugetlb_alloc_buddy_huge_page has to deal with
two different allocation modes - one for memory policy and other node
specific (or to make it more obscure node non-specific) requests.
This just screams for a reorganization.
This patch pulls out all the vma specific handling up to
__alloc_buddy_huge_page_with_mpol where it belongs.
__alloc_buddy_huge_page will get nodemask argument and
__hugetlb_alloc_buddy_huge_page will become a trivial wrapper over the
page allocator.
In short:
__alloc_buddy_huge_page_with_mpol - memory policy handling
__alloc_buddy_huge_page - overcommit handling and accounting
__hugetlb_alloc_buddy_huge_page - page allocator layer
Also note that __hugetlb_alloc_buddy_huge_page and its cpuset retry loop
is not really needed because the page allocator already handles the
cpusets update.
Finally __hugetlb_alloc_buddy_huge_page had a special case for node
specific allocations (when no policy is applied and there is a node
given). This has relied on __GFP_THISNODE to not fallback to a different
node. alloc_huge_page_node is the only caller which relies on this
behavior so move the __GFP_THISNODE there.
Not only does this remove quite some code it also should make those
layers easier to follow and clear wrt responsibilities.
Link: http://lkml.kernel.org/r/20170622193034.28972-2-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Tested-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9077865..fd6e0c50 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1521,82 +1521,19 @@ int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
return rc;
}
-/*
- * There are 3 ways this can get called:
- * 1. With vma+addr: we use the VMA's memory policy
- * 2. With !vma, but nid=NUMA_NO_NODE: We try to allocate a huge
- * page from any node, and let the buddy allocator itself figure
- * it out.
- * 3. With !vma, but nid!=NUMA_NO_NODE. We allocate a huge page
- * strictly from 'nid'
- */
static struct page *__hugetlb_alloc_buddy_huge_page(struct hstate *h,
- struct vm_area_struct *vma, unsigned long addr, int nid)
+ gfp_t gfp_mask, int nid, nodemask_t *nmask)
{
int order = huge_page_order(h);
- gfp_t gfp = htlb_alloc_mask(h)|__GFP_COMP|__GFP_REPEAT|__GFP_NOWARN;
- unsigned int cpuset_mems_cookie;
- /*
- * We need a VMA to get a memory policy. If we do not
- * have one, we use the 'nid' argument.
- *
- * The mempolicy stuff below has some non-inlined bits
- * and calls ->vm_ops. That makes it hard to optimize at
- * compile-time, even when NUMA is off and it does
- * nothing. This helps the compiler optimize it out.
- */
- if (!IS_ENABLED(CONFIG_NUMA) || !vma) {
- /*
- * If a specific node is requested, make sure to
- * get memory from there, but only when a node
- * is explicitly specified.
- */
- if (nid != NUMA_NO_NODE)
- gfp |= __GFP_THISNODE;
- /*
- * Make sure to call something that can handle
- * nid=NUMA_NO_NODE
- */
- return alloc_pages_node(nid, gfp, order);
- }
-
- /*
- * OK, so we have a VMA. Fetch the mempolicy and try to
- * allocate a huge page with it. We will only reach this
- * when CONFIG_NUMA=y.
- */
- do {
- struct page *page;
- struct mempolicy *mpol;
- int nid;
- nodemask_t *nodemask;
-
- cpuset_mems_cookie = read_mems_allowed_begin();
- nid = huge_node(vma, addr, gfp, &mpol, &nodemask);
- mpol_cond_put(mpol);
- page = __alloc_pages_nodemask(gfp, order, nid, nodemask);
- if (page)
- return page;
- } while (read_mems_allowed_retry(cpuset_mems_cookie));
-
- return NULL;
+ gfp_mask |= __GFP_COMP|__GFP_REPEAT|__GFP_NOWARN;
+ if (nid == NUMA_NO_NODE)
+ nid = numa_mem_id();
+ return __alloc_pages_nodemask(gfp_mask, order, nid, nmask);
}
-/*
- * There are two ways to allocate a huge page:
- * 1. When you have a VMA and an address (like a fault)
- * 2. When you have no VMA (like when setting /proc/.../nr_hugepages)
- *
- * 'vma' and 'addr' are only for (1). 'nid' is always NUMA_NO_NODE in
- * this case which signifies that the allocation should be done with
- * respect for the VMA's memory policy.
- *
- * For (2), we ignore 'vma' and 'addr' and use 'nid' exclusively. This
- * implies that memory policies will not be taken in to account.
- */
-static struct page *__alloc_buddy_huge_page(struct hstate *h,
- struct vm_area_struct *vma, unsigned long addr, int nid)
+static struct page *__alloc_buddy_huge_page(struct hstate *h, gfp_t gfp_mask,
+ int nid, nodemask_t *nmask)
{
struct page *page;
unsigned int r_nid;
@@ -1605,15 +1542,6 @@ static struct page *__alloc_buddy_huge_page(struct hstate *h,
return NULL;
/*
- * Make sure that anyone specifying 'nid' is not also specifying a VMA.
- * This makes sure the caller is picking _one_ of the modes with which
- * we can call this function, not both.
- */
- if (vma || (addr != -1)) {
- VM_WARN_ON_ONCE(addr == -1);
- VM_WARN_ON_ONCE(nid != NUMA_NO_NODE);
- }
- /*
* Assume we will successfully allocate the surplus page to
* prevent racing processes from causing the surplus to exceed
* overcommit
@@ -1646,7 +1574,7 @@ static struct page *__alloc_buddy_huge_page(struct hstate *h,
}
spin_unlock(&hugetlb_lock);
- page = __hugetlb_alloc_buddy_huge_page(h, vma, addr, nid);
+ page = __hugetlb_alloc_buddy_huge_page(h, gfp_mask, nid, nmask);
spin_lock(&hugetlb_lock);
if (page) {
@@ -1671,26 +1599,23 @@ static struct page *__alloc_buddy_huge_page(struct hstate *h,
}
/*
- * Allocate a huge page from 'nid'. Note, 'nid' may be
- * NUMA_NO_NODE, which means that it may be allocated
- * anywhere.
- */
-static
-struct page *__alloc_buddy_huge_page_no_mpol(struct hstate *h, int nid)
-{
- unsigned long addr = -1;
-
- return __alloc_buddy_huge_page(h, NULL, addr, nid);
-}
-
-/*
* Use the VMA's mpolicy to allocate a huge page from the buddy.
*/
static
struct page *__alloc_buddy_huge_page_with_mpol(struct hstate *h,
struct vm_area_struct *vma, unsigned long addr)
{
- return __alloc_buddy_huge_page(h, vma, addr, NUMA_NO_NODE);
+ struct page *page;
+ struct mempolicy *mpol;
+ gfp_t gfp_mask = htlb_alloc_mask(h);
+ int nid;
+ nodemask_t *nodemask;
+
+ nid = huge_node(vma, addr, gfp_mask, &mpol, &nodemask);
+ page = __alloc_buddy_huge_page(h, gfp_mask, nid, nodemask);
+ mpol_cond_put(mpol);
+
+ return page;
}
/*
@@ -1700,21 +1625,26 @@ struct page *__alloc_buddy_huge_page_with_mpol(struct hstate *h,
*/
struct page *alloc_huge_page_node(struct hstate *h, int nid)
{
+ gfp_t gfp_mask = htlb_alloc_mask(h);
struct page *page = NULL;
+ if (nid != NUMA_NO_NODE)
+ gfp_mask |= __GFP_THISNODE;
+
spin_lock(&hugetlb_lock);
if (h->free_huge_pages - h->resv_huge_pages > 0)
page = dequeue_huge_page_node(h, nid);
spin_unlock(&hugetlb_lock);
if (!page)
- page = __alloc_buddy_huge_page_no_mpol(h, nid);
+ page = __alloc_buddy_huge_page(h, gfp_mask, nid, NULL);
return page;
}
-struct page *alloc_huge_page_nodemask(struct hstate *h, const nodemask_t *nmask)
+struct page *alloc_huge_page_nodemask(struct hstate *h, nodemask_t *nmask)
{
+ gfp_t gfp_mask = htlb_alloc_mask(h);
struct page *page = NULL;
int node;
@@ -1731,13 +1661,7 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, const nodemask_t *nmask)
return page;
/* No reservations, try to overcommit */
- for_each_node_mask(node, *nmask) {
- page = __alloc_buddy_huge_page_no_mpol(h, node);
- if (page)
- return page;
- }
-
- return NULL;
+ return __alloc_buddy_huge_page(h, gfp_mask, NUMA_NO_NODE, nmask);
}
/*
@@ -1765,7 +1689,8 @@ 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_no_mpol(h, NUMA_NO_NODE);
+ page = __alloc_buddy_huge_page(h, htlb_alloc_mask(h),
+ NUMA_NO_NODE, NULL);
if (!page) {
alloc_ok = false;
break;