On Thu, Jul 09, 2009 at 02:30:20PM +0100, Mel Gorman wrote:
> On Wed, Jul 08, 2009 at 03:24:46PM -0400, Lee Schermerhorn wrote:
> > [PATCH 2/3] hugetlb: derive huge pages nodes allowed from task mempolicy
> >
> > Against: 25jun09 mmotm atop the "hugetlb: balance freeing..." series
> >
> > V2:
> > + cleaned up comments, removed some deemed unnecessary,
> > add some suggested by review
> > + removed check for !current in huge_mpol_nodes_allowed().
> > + added 'current->comm' to warning message in huge_mpol_nodes_allowed().
> > + added VM_BUG_ON() assertion in hugetlb.c next_node_allowed() to
> > catch out of range node id.
> > + add examples to patch description
> >
> > This patch derives a "nodes_allowed" node mask from the numa
> > mempolicy of the task modifying the number of persistent huge
> > pages to control the allocation, freeing and adjusting of surplus
> > huge pages. This mask is derived as follows:
> >
> > * For "default" [NULL] task mempolicy, a NULL nodemask_t pointer
> > is produced. This will cause the hugetlb subsystem to use
> > node_online_map as the "nodes_allowed". This preserves the
> > behavior before this patch.
> > * For "preferred" mempolicy, including explicit local allocation,
> > a nodemask with the single preferred node will be produced.
> > "local" policy will NOT track any internode migrations of the
> > task adjusting nr_hugepages.
> > * For "bind" and "interleave" policy, the mempolicy's nodemask
> > will be used.
> > * Other than to inform the construction of the nodes_allowed node
> > mask, the actual mempolicy mode is ignored. That is, all modes
> > behave like interleave over the resulting nodes_allowed mask
> > with no "fallback".
> >
> > Because we may have allocated or freed a huge page with a
> > different policy/nodes_allowed previously, we always need to
> > check that the next_node_to_{alloc|free} exists in the current
> > nodes_allowed mask. To avoid duplication of code, this is done
> > in the hstate_next_node_to_{alloc|free}() functions. So,
> > these functions have been modified to allow them to be called
> > to obtain the "start_nid". Then, whereas prior to this patch
> > we unconditionally called hstate_next_node_to_{alloc|free}(),
> > whether or not we successfully allocated/freed a huge page on
> > the node, now we only call these functions on failure to alloc/free.
> >
> > Notes:
> >
> > 1) This patch introduces a subtle change in behavior: huge page
> > allocation and freeing will be constrained by any mempolicy
> > that the task adjusting the huge page pool inherits from its
> > parent. This policy could come from a distant ancestor. The
> > adminstrator adjusting the huge page pool without explicitly
> > specifying a mempolicy via numactl might be surprised by this.
> > Additionaly, any mempolicy specified by numactl will be
> > constrained by the cpuset in which numactl is invoked.
> >
> > 2) Hugepages allocated at boot time use the node_online_map.
> > An additional patch could implement a temporary boot time
> > huge pages nodes_allowed command line parameter.
> >
> > 3) Using mempolicy to control persistent huge page allocation
> > and freeing requires no change to hugeadm when invoking
> > it via numactl, as shown in the examples below. However,
> > hugeadm could be enhanced to take the allowed nodes as an
> > argument and set its task mempolicy itself. This would allow
> > it to detect and warn about any non-default mempolicy that it
> > inherited from its parent, thus alleviating the issue described
> > in Note 1 above.
> >
> > See the updated documentation [next patch] for more information
> > about the implications of this patch.
> >
> > Examples:
> >
> > Starting with:
> >
> > Node 0 HugePages_Total: 0
> > Node 1 HugePages_Total: 0
> > Node 2 HugePages_Total: 0
> > Node 3 HugePages_Total: 0
> >
> > Default behavior [with or without this patch] balances persistent
> > hugepage allocation across nodes [with sufficient contiguous memory]:
> >
> > hugeadm --pool-pages-min=2048Kb:32
> >
> > yields:
> >
> > Node 0 HugePages_Total: 8
> > Node 1 HugePages_Total: 8
> > Node 2 HugePages_Total: 8
> > Node 3 HugePages_Total: 8
> >
> > Applying mempolicy--e.g., with numactl [using '-m' a.k.a.
> > '--membind' because it allows multiple nodes to be specified
> > and it's easy to type]--we can allocate huge pages on
> > individual nodes or sets of nodes. So, starting from the
> > condition above, with 8 huge pages per node:
> >
> > numactl -m 2 hugeadm --pool-pages-min=2048Kb:+8
> >
> > yields:
> >
> > Node 0 HugePages_Total: 8
> > Node 1 HugePages_Total: 8
> > Node 2 HugePages_Total: 16
> > Node 3 HugePages_Total: 8
> >
> > The incremental 8 huge pages were restricted to node 2 by the
> > specified mempolicy.
> >
> > Similarly, we can use mempolicy to free persistent huge pages
> > from specified nodes:
> >
> > numactl -m 0,1 hugeadm --pool-pages-min=2048Kb:-8
> >
> > yields:
> >
> > Node 0 HugePages_Total: 4
> > Node 1 HugePages_Total: 4
> > Node 2 HugePages_Total: 16
> > Node 3 HugePages_Total: 8
> >
> > The 8 huge pages freed were balanced over nodes 0 and 1.
> >
> > Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
> >
>
> Much better changelog.
>
> Reading through, the main problem I can see is that the reservation
> calculations are still not nodemask aware. This means that mmap() can return
> successfully and the process that called mmap() get unexpectedly killed
> because while there were enough hugepages overall, there were not enough in
> the pools allowed by the nodemask. This is a stability problem for those that
> create hugepage pools on one set of nodes and run applications on a subset.
> Minimally, can this situation be warned about and a note in the documentation
> about it?
>
> Testing with it, I couldn't break it as such but libhugetlbfs is showing up
> an anomaly with the counters tests. Some investigation showed that it was
> because when it shrinks the pool, one page gets accounted for as a surplus
> page which was unexpected.
>
> I only got as far as determining the problem was in the patches that free
> pages in a round-robin fashion but then ran out of time on the machine. I'll
> see can I reproduce using fake-numa on a normal x86-64 instead of a real
> NUMA machine but maybe you have a fix for this problem already?
>
Bah, you did. After I hit send, I remembered you sent one out and I didn't
pick it up properly. The counters tests works as expected now. I'll keep
testing but other than the stability problem when running on a subset of
nodes with hugepages, this looks good to me.
Reviewed-by: Mel Gorman <mel@xxxxxxxxx>
> > include/linux/mempolicy.h | 3 +
> > mm/hugetlb.c | 101 +++++++++++++++++++++++++++++++---------------
> > mm/mempolicy.c | 61 +++++++++++++++++++++++++++
> > 3 files changed, 133 insertions(+), 32 deletions(-)
> >
> > Index: linux-2.6.31-rc1-mmotm-090625-1549/mm/hugetlb.c
> > ===================================================================
> > --- linux-2.6.31-rc1-mmotm-090625-1549.orig/mm/hugetlb.c 2009-07-07 09:58:17.000000000 -0400
> > +++ linux-2.6.31-rc1-mmotm-090625-1549/mm/hugetlb.c 2009-07-07 13:25:41.000000000 -0400
> > @@ -621,29 +621,54 @@ static struct page *alloc_fresh_huge_pag
> > }
> >
> > /*
> > + * common helper functions for hstate_next_node_to_{alloc|free}.
> > + * We may have allocated or freed a huge pages based on a different
> > + * nodes_allowed, previously, so h->next_node_to_{alloc|free} might
> > + * be outside of *nodes_allowed. Ensure that we use the next
> > + * 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 this_node_allowed(int nid, nodemask_t *nodes_allowed)
> > +{
> > + if (!node_isset(nid, *nodes_allowed))
> > + nid = next_node_allowed(nid, nodes_allowed);
> > + return nid;
> > +}
> > +
> > +/*
> > * Use a helper variable to find the next node and then
> > * copy it back to next_nid_to_alloc afterwards:
> > * otherwise there's a window in which a racer might
> > * pass invalid nid MAX_NUMNODES to alloc_pages_exact_node.
> > * But we don't need to use a spin_lock here: it really
> > * doesn't matter if occasionally a racer chooses the
> > - * same nid as we do. Move nid forward in the mask even
> > - * if we just successfully allocated a hugepage so that
> > - * the next caller gets hugepages on the next node.
> > + * same nid as we do. Move nid forward in the mask whether
> > + * or not we just successfully allocated a hugepage so that
> > + * the next allocation addresses the next node.
> > */
> > static int hstate_next_node_to_alloc(struct hstate *h,
> > nodemask_t *nodes_allowed)
> > {
> > - int next_nid;
> > + int nid, next_nid;
> >
> > if (!nodes_allowed)
> > nodes_allowed = &node_online_map;
> >
> > - next_nid = next_node(h->next_nid_to_alloc, *nodes_allowed);
> > - if (next_nid == MAX_NUMNODES)
> > - next_nid = first_node(*nodes_allowed);
> > + nid = this_node_allowed(h->next_nid_to_alloc, nodes_allowed);
> > +
> > + next_nid = next_node_allowed(nid, nodes_allowed);
> > h->next_nid_to_alloc = next_nid;
> > - return next_nid;
> > +
> > + return nid;
> > }
> >
> > static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
> > @@ -653,15 +678,17 @@ static int alloc_fresh_huge_page(struct
> > int next_nid;
> > int ret = 0;
> >
> > - start_nid = h->next_nid_to_alloc;
> > + start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> > next_nid = start_nid;
> >
> > do {
> > page = alloc_fresh_huge_page_node(h, next_nid);
> > - if (page)
> > + if (page) {
> > ret = 1;
> > + break;
> > + }
> > next_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> > - } while (!page && next_nid != start_nid);
> > + } while (next_nid != start_nid);
> >
> > if (ret)
> > count_vm_event(HTLB_BUDDY_PGALLOC);
> > @@ -672,21 +699,23 @@ static int alloc_fresh_huge_page(struct
> > }
> >
> > /*
> > - * helper for free_pool_huge_page() - find next node
> > - * from which to free a huge page
> > + * helper for free_pool_huge_page() - return the next 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 next_nid;
> > + int nid, next_nid;
> >
> > if (!nodes_allowed)
> > nodes_allowed = &node_online_map;
> >
> > - next_nid = next_node(h->next_nid_to_free, *nodes_allowed);
> > - if (next_nid == MAX_NUMNODES)
> > - next_nid = first_node(*nodes_allowed);
> > + nid = this_node_allowed(h->next_nid_to_free, nodes_allowed);
> > + next_nid = next_node_allowed(nid, nodes_allowed);
> > h->next_nid_to_free = next_nid;
> > - return next_nid;
> > +
> > + return nid;
> > }
> >
> > /*
> > @@ -702,7 +731,7 @@ static int free_pool_huge_page(struct hs
> > int next_nid;
> > int ret = 0;
> >
> > - start_nid = h->next_nid_to_free;
> > + start_nid = hstate_next_node_to_free(h, nodes_allowed);
> > next_nid = start_nid;
> >
> > do {
> > @@ -724,9 +753,10 @@ static int free_pool_huge_page(struct hs
> > }
> > update_and_free_page(h, page);
> > ret = 1;
> > + break;
> > }
> > next_nid = hstate_next_node_to_free(h, nodes_allowed);
> > - } while (!ret && next_nid != start_nid);
> > + } while (next_nid != start_nid);
> >
> > return ret;
> > }
> > @@ -1037,10 +1067,9 @@ int __weak alloc_bootmem_huge_page(struc
> > void *addr;
> >
> > addr = __alloc_bootmem_node_nopanic(
> > - NODE_DATA(h->next_nid_to_alloc),
> > + NODE_DATA(hstate_next_node_to_alloc(h, NULL)),
> > huge_page_size(h), huge_page_size(h), 0);
> >
> > - hstate_next_node_to_alloc(h, NULL); /* always advance nid */
> > if (addr) {
> > /*
> > * Use the beginning of the huge page to store the
> > @@ -1177,29 +1206,33 @@ static int adjust_pool_surplus(struct hs
> > VM_BUG_ON(delta != -1 && delta != 1);
> >
> > if (delta < 0)
> > - start_nid = h->next_nid_to_alloc;
> > + start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> > else
> > - start_nid = h->next_nid_to_free;
> > + start_nid = hstate_next_node_to_free(h, nodes_allowed);
> > next_nid = start_nid;
> >
> > do {
> > int nid = next_nid;
> > if (delta < 0) {
> > - next_nid = hstate_next_node_to_alloc(h, nodes_allowed);
> > /*
> > * To shrink on this node, there must be a surplus page
> > */
> > - if (!h->surplus_huge_pages_node[nid])
> > + if (!h->surplus_huge_pages_node[nid]) {
> > + next_nid = hstate_next_node_to_alloc(h,
> > + nodes_allowed);
> > continue;
> > + }
> > }
> > if (delta > 0) {
> > - next_nid = hstate_next_node_to_free(h, nodes_allowed);
> > /*
> > * Surplus cannot exceed the total number of pages
> > */
> > if (h->surplus_huge_pages_node[nid] >=
> > - h->nr_huge_pages_node[nid])
> > + h->nr_huge_pages_node[nid]) {
> > + next_nid = hstate_next_node_to_free(h,
> > + nodes_allowed);
> > continue;
> > + }
> > }
> >
> > h->surplus_huge_pages += delta;
> > @@ -1215,10 +1248,13 @@ static int adjust_pool_surplus(struct hs
> > static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count)
> > {
> > unsigned long min_count, ret;
> > + nodemask_t *nodes_allowed;
> >
> > if (h->order >= MAX_ORDER)
> > return h->max_huge_pages;
> >
> > + nodes_allowed = huge_mpol_nodes_allowed();
> > +
> > /*
> > * Increase the pool size
> > * First take pages out of surplus state. Then make up the
> > @@ -1232,7 +1268,7 @@ static unsigned long set_max_huge_pages(
> > */
> > spin_lock(&hugetlb_lock);
> > while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
> > - if (!adjust_pool_surplus(h, NULL, -1))
> > + if (!adjust_pool_surplus(h, nodes_allowed, -1))
> > break;
> > }
> >
> > @@ -1243,7 +1279,7 @@ static unsigned long set_max_huge_pages(
> > * and reducing the surplus.
> > */
> > spin_unlock(&hugetlb_lock);
> > - ret = alloc_fresh_huge_page(h, NULL);
> > + ret = alloc_fresh_huge_page(h, nodes_allowed);
> > spin_lock(&hugetlb_lock);
> > if (!ret)
> > goto out;
> > @@ -1269,16 +1305,17 @@ static unsigned long set_max_huge_pages(
> > min_count = max(count, min_count);
> > try_to_free_low(h, min_count);
> > while (min_count < persistent_huge_pages(h)) {
> > - if (!free_pool_huge_page(h, NULL, 0))
> > + if (!free_pool_huge_page(h, nodes_allowed, 0))
> > break;
> > }
> > while (count < persistent_huge_pages(h)) {
> > - if (!adjust_pool_surplus(h, NULL, 1))
> > + if (!adjust_pool_surplus(h, nodes_allowed, 1))
> > break;
> > }
> > out:
> > ret = persistent_huge_pages(h);
> > spin_unlock(&hugetlb_lock);
> > + kfree(nodes_allowed);
> > return ret;
> > }
> >
> > Index: linux-2.6.31-rc1-mmotm-090625-1549/mm/mempolicy.c
> > ===================================================================
> > --- linux-2.6.31-rc1-mmotm-090625-1549.orig/mm/mempolicy.c 2009-07-07 09:46:48.000000000 -0400
> > +++ linux-2.6.31-rc1-mmotm-090625-1549/mm/mempolicy.c 2009-07-07 13:48:06.000000000 -0400
> > @@ -1544,6 +1544,67 @@ struct zonelist *huge_zonelist(struct vm
> > }
> > return zl;
> > }
> > +
> > +/*
> > + * huge_mpol_nodes_allowed -- mempolicy extension for huge pages.
> > + *
> > + * Returns a [pointer to a] nodelist based on the current task's mempolicy
> > + * to constraing the allocation and freeing of persistent huge pages
> > + * 'Preferred', 'local' and 'interleave' mempolicy will behave more like
> > + * 'bind' policy in this context. An attempt to allocate a persistent huge
> > + * page will never "fallback" to another node inside the buddy system
> > + * allocator.
> > + *
> > + * If the task's mempolicy is "default" [NULL], just return NULL for
> > + * default behavior. Otherwise, extract the policy nodemask for 'bind'
> > + * or 'interleave' policy or construct a nodemask for 'preferred' or
> > + * 'local' policy and return a pointer to a kmalloc()ed nodemask_t.
> > + *
> > + * N.B., it is the caller's responsibility to free a returned nodemask.
> > + */
> > +nodemask_t *huge_mpol_nodes_allowed(void)
> > +{
> > + nodemask_t *nodes_allowed = NULL;
> > + struct mempolicy *mempolicy;
> > + int nid;
> > +
> > + if (!current->mempolicy)
> > + return NULL;
> > +
> > + mpol_get(current->mempolicy);
> > + nodes_allowed = kmalloc(sizeof(*nodes_allowed), GFP_KERNEL);
> > + if (!nodes_allowed) {
> > + printk(KERN_WARNING "%s unable to allocate nodes allowed mask "
> > + "for huge page allocation.\nFalling back to default.\n",
> > + current->comm);
> > + goto out;
> > + }
> > + nodes_clear(*nodes_allowed);
> > +
> > + mempolicy = current->mempolicy;
> > + switch(mempolicy->mode) {
> > + case MPOL_PREFERRED:
> > + if (mempolicy->flags & MPOL_F_LOCAL)
> > + nid = numa_node_id();
> > + else
> > + nid = mempolicy->v.preferred_node;
> > + node_set(nid, *nodes_allowed);
> > + break;
> > +
> > + case MPOL_BIND:
> > + /* Fall through */
> > + case MPOL_INTERLEAVE:
> > + *nodes_allowed = mempolicy->v.nodes;
> > + break;
> > +
> > + default:
> > + BUG();
> > + }
> > +
> > +out:
> > + mpol_put(current->mempolicy);
> > + return nodes_allowed;
> > +}
> > #endif
> >
> > /* Allocate a page in interleaved policy.
> > Index: linux-2.6.31-rc1-mmotm-090625-1549/include/linux/mempolicy.h
> > ===================================================================
> > --- linux-2.6.31-rc1-mmotm-090625-1549.orig/include/linux/mempolicy.h 2009-07-06 13:05:23.000000000 -0400
> > +++ linux-2.6.31-rc1-mmotm-090625-1549/include/linux/mempolicy.h 2009-07-07 09:58:32.000000000 -0400
> > @@ -201,6 +201,7 @@ extern void mpol_fix_fork_child_flag(str
> > extern struct zonelist *huge_zonelist(struct vm_area_struct *vma,
> > unsigned long addr, gfp_t gfp_flags,
> > struct mempolicy **mpol, nodemask_t **nodemask);
> > +extern nodemask_t *huge_mpol_nodes_allowed(void);
> > extern unsigned slab_node(struct mempolicy *policy);
> >
> > extern enum zone_type policy_zone;
> > @@ -328,6 +329,8 @@ static inline struct zonelist *huge_zone
> > return node_zonelist(0, gfp_flags);
> > }
> >
> > +static inline nodemask_t *huge_mpol_nodes_allowed(void) { return NULL; }
> > +
> > static inline int do_migrate_pages(struct mm_struct *mm,
> > const nodemask_t *from_nodes,
> > const nodemask_t *to_nodes, int flags)
> >
>
> --
> Mel Gorman
> Part-time Phd Student Linux Technology Center
> University of Limerick IBM Dublin Software Lab
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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