On Tue, Sep 25, 2018 at 02:03:26PM +0200, Michal Hocko wrote:
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index c3bc7e9c9a2a..c0bcede31930 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -629,21 +629,40 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct
> vm_fault *vmf,
> * available
> * never: never stall for any thp allocation
> */
> -static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
> +static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct
> *vma, unsigned long addr)
> {
> const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
> + gfp_t this_node = 0;
> +
> +#ifdef CONFIG_NUMA
> + struct mempolicy *pol;
> + /*
> + * __GFP_THISNODE is used only when __GFP_DIRECT_RECLAIM is not
> + * specified, to express a general desire to stay on the current
> + * node for optimistic allocation attempts. If the defrag mode
> + * and/or madvise hint requires the direct reclaim then we prefer
> + * to fallback to other node rather than node reclaim because that
> + * can lead to excessive reclaim even though there is free memory
> + * on other nodes. We expect that NUMA preferences are specified
> + * by memory policies.
> + */
> + pol = get_vma_policy(vma, addr);
> + if (pol->mode != MPOL_BIND)
> + this_node = __GFP_THISNODE;
> + mpol_cond_put(pol);
> +#endif
I'm not very good with NUMA policies. Could you explain in more details how
the code above is equivalent to the code below?
...
> @@ -2026,60 +2025,6 @@ alloc_pages_vma(gfp_t gfp, int order, struct
> vm_area_struct *vma,
> goto out;
> }
>
> - if (unlikely(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hugepage)) {
> - int hpage_node = node;
> -
> - /*
> - * For hugepage allocation and non-interleave policy which
> - * allows the current node (or other explicitly preferred
> - * node) we only try to allocate from the current/preferred
> - * node and don't fall back to other nodes, as the cost of
> - * remote accesses would likely offset THP benefits.
> - *
> - * If the policy is interleave, or does not allow the current
> - * node in its nodemask, we allocate the standard way.
> - */
> - if (pol->mode == MPOL_PREFERRED &&
> - !(pol->flags & MPOL_F_LOCAL))
> - hpage_node = pol->v.preferred_node;
> -
> - nmask = policy_nodemask(gfp, pol);
> - if (!nmask || node_isset(hpage_node, *nmask)) {
> - mpol_cond_put(pol);
> - /*
> - * We cannot invoke reclaim if __GFP_THISNODE
> - * is set. Invoking reclaim with
> - * __GFP_THISNODE set, would cause THP
> - * allocations to trigger heavy swapping
> - * despite there may be tons of free memory
> - * (including potentially plenty of THP
> - * already available in the buddy) on all the
> - * other NUMA nodes.
> - *
> - * At most we could invoke compaction when
> - * __GFP_THISNODE is set (but we would need to
> - * refrain from invoking reclaim even if
> - * compaction returned COMPACT_SKIPPED because
> - * there wasn't not enough memory to succeed
> - * compaction). For now just avoid
> - * __GFP_THISNODE instead of limiting the
> - * allocation path to a strict and single
> - * compaction invocation.
> - *
> - * Supposedly if direct reclaim was enabled by
> - * the caller, the app prefers THP regardless
> - * of the node it comes from so this would be
> - * more desiderable behavior than only
> - * providing THP originated from the local
> - * node in such case.
> - */
> - if (!(gfp & __GFP_DIRECT_RECLAIM))
> - gfp |= __GFP_THISNODE;
> - page = __alloc_pages_node(hpage_node, gfp, order);
> - goto out;
> - }
> - }
> -
> nmask = policy_nodemask(gfp, pol);
> preferred_nid = policy_node(gfp, pol, node);
> page = __alloc_pages_nodemask(gfp, order, preferred_nid, nmask);
--
Kirill A. Shutemov
