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mm, hugetlb: unclutter hugetlb allocation layers

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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>
This commit is contained in:
Michal Hocko 2017-07-10 15:49:08 -07:00 committed by Linus Torvalds
parent 422580c3ce
commit aaf14e40a3
2 changed files with 30 additions and 105 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/hugetlb.h
View File

@ -349,7 +349,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
struct page *alloc_huge_page_node(struct hstate *h, int nid);
struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
unsigned long addr, int avoid_reserve);
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);
int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
pgoff_t idx);

133
mm/hugetlb.c
View File

@ -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;
@ -1604,15 +1541,6 @@ static struct page *__alloc_buddy_huge_page(struct hstate *h,
if (hstate_is_gigantic(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
@ -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) {
@ -1670,19 +1598,6 @@ static struct page *__alloc_buddy_huge_page(struct hstate *h,
return page;
}
/*
* 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.
*/
@ -1690,7 +1605,17 @@ 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;