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SubjectRe: [PATCH 3/3] mm: Enable Buddy allocation isolation for CDM nodes
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On 02/08/2017 03:01 PM, Anshuman Khandual wrote:
> This implements allocation isolation for CDM nodes in buddy allocator by
> discarding CDM memory zones all the time except in the cases where the gfp
> flag has got __GFP_THISNODE or the nodemask contains CDM nodes in cases
> where it is non NULL (explicit allocation request in the kernel or user
> process MPOL_BIND policy based requests).
>
> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
> ---
> mm/page_alloc.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 40908de..7d8c82a 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -64,6 +64,7 @@
> #include <linux/page_owner.h>
> #include <linux/kthread.h>
> #include <linux/memcontrol.h>
> +#include <linux/node.h>
>
> #include <asm/sections.h>
> #include <asm/tlbflush.h>
> @@ -2908,6 +2909,24 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
> struct page *page;
> unsigned long mark;
>
> + /*
> + * CDM nodes get skipped if the requested gfp flag
> + * does not have __GFP_THISNODE set or the nodemask
> + * does not have any CDM nodes in case the nodemask
> + * is non NULL (explicit allocation requests from
> + * kernel or user process MPOL_BIND policy which has
> + * CDM nodes).
> + */
> + if (is_cdm_node(zone->zone_pgdat->node_id)) {
> + if (!(gfp_mask & __GFP_THISNODE)) {
> + if (!ac->nodemask)
> + continue;
> +
> + if (!nodemask_has_cdm(*ac->nodemask))
> + continue;

nodemask_has_cdm() looks quite expensive, combined with the loop here that's
O(n^2). But I don't understand why you need it. If there is no cdm node in the
nodemask, then we never reach this code with a cdm node, because the zonelist
iterator already checks the nodemask? Am I missing something?

> + }
> + }
> +
> if (cpusets_enabled() &&
> (alloc_flags & ALLOC_CPUSET) &&
> !__cpuset_zone_allowed(zone, gfp_mask))
>

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