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    SubjectRe: [PATCH 3/4] mm: unify new_node_page and alloc_migrate_target
    On Thu 08-06-17 10:36:13, Vlastimil Babka wrote:
    > On 06/08/2017 09:45 AM, Michal Hocko wrote:
    > > From: Michal Hocko <mhocko@suse.com>
    > >
    > > 394e31d2ceb4 ("mem-hotplug: alloc new page from a nearest neighbor node
    > > when mem-offline") has duplicated a large part of alloc_migrate_target
    > > with some hotplug specific special casing. To be more precise it tried
    > > to enfore the allocation from a different node than the original page.
    > > As a result the two function diverged in their shared logic, e.g. the
    > > hugetlb allocation strategy. Let's unify the two and express different
    > > NUMA requirements by the given nodemask. new_node_page will simply
    > > exclude the node it doesn't care about and alloc_migrate_target will
    > > use all the available nodes. alloc_migrate_target will then learn to
    > > migrate hugetlb pages more sanely and use preallocated pool when
    > > possible.
    > >
    > > Please note that alloc_migrate_target used to call alloc_page resp.
    > > alloc_pages_current so the memory policy of the current context which
    > > is quite strange when we consider that it is used in the context of
    > > alloc_contig_range which just tries to migrate pages which stand in the
    > > way.
    > >
    > > Signed-off-by: Michal Hocko <mhocko@suse.com>
    >
    > Acked-by: Vlastimil Babka <vbabka@suse.cz>

    Thanks!

    > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c
    > > index 3606104893e0..757410d9f758 100644
    > > --- a/mm/page_isolation.c
    > > +++ b/mm/page_isolation.c
    > > @@ -8,6 +8,7 @@
    > > #include <linux/memory.h>
    > > #include <linux/hugetlb.h>
    > > #include <linux/page_owner.h>
    > > +#include <linux/migrate.h>
    > > #include "internal.h"
    > >
    > > #define CREATE_TRACE_POINTS
    > > @@ -294,20 +295,5 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
    > > struct page *alloc_migrate_target(struct page *page, unsigned long private,
    > > int **resultp)
    > > {
    > > - gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
    > > -
    > > - /*
    > > - * TODO: allocate a destination hugepage from a nearest neighbor node,
    > > - * accordance with memory policy of the user process if possible. For
    > > - * now as a simple work-around, we use the next node for destination.
    > > - */
    > > - if (PageHuge(page))
    > > - return alloc_huge_page_node(page_hstate(compound_head(page)),
    > > - next_node_in(page_to_nid(page),
    > > - node_online_map));
    > > -
    > > - if (PageHighMem(page))
    > > - gfp_mask |= __GFP_HIGHMEM;
    > > -
    > > - return alloc_page(gfp_mask);
    > > + return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);
    >
    > This replaces the N_ONLINE (node_online_map) with N_MEMORY for huge
    > pages. Assuming that's OK.

    Yes, this is what 231e97e2b8ec ("mem-hotplug: use nodes that contain
    memory as mask in new_node_page()") fixed in new_node_page and didn't
    care to do on alloc_migrate_target. Another argument to remove the code
    duplication. Thanks for pointing out anyway!

    --
    Michal Hocko
    SUSE Labs

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