On 02/10/2017 11:06 AM, 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@xxxxxxxxxxxxxxxxxx>
> ---
> mm/page_alloc.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 84d61bb..392c24a 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 +2909,21 @@ 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;
> + }
> + }
With the current cpuset implementation, this will have a subtle corner
case when allocating from a cpuset that allows the cdm node, and there
is no (task or vma) mempolicy applied for the allocation. In the fast
path (__alloc_pages_nodemask()) we'll set ac->nodemask to
current->mems_allowed, so your code will wrongly assume that this
ac->nodemask is a policy that allows the CDM node. Probably not what you
want?
This might change if we decide to fix the cpuset vs mempolicy issues [1]
so your input on that topic with your recent experience with all the
alternative CDM isolation implementations would be useful. Thanks.
[1] http://www.spinics.net/lists/linux-mm/msg121760.html
> if (cpusets_enabled() &&
> (alloc_flags & ALLOC_CPUSET) &&
> !__cpuset_zone_allowed(zone, gfp_mask))
>
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