On Wed, 19 Jan 2011, KOSAKI Motohiro wrote:
> I'm glad to you are keeping fastpath concern. However you don't need
> nodemask-and in this case. Because zonelist->zref[0] is always in nodemask.
> Please see policy_zonelist(). So, you can just replace nodemask with cpuset_mems_allowed.
>
> This is not only simple, but also improve a consisteny of mempolicy.
>
mempolicies have nothing to do with this, they pass their nodemask into
the page allocator so the preferred_zone is already allowed; setting a
mempolicy with a nodemask that is disallowed by the cpuset is an invalid
configuration.
> ---
> mm/page_alloc.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 07a6544..876de04 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2146,7 +2146,8 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
>
> get_mems_allowed();
> /* The preferred zone is used for statistics later */
> - first_zones_zonelist(zonelist, high_zoneidx, nodemask, &preferred_zone);
> + first_zones_zonelist(zonelist, high_zoneidx,
> + &cpuset_current_mems_allowed, &preferred_zone);
> if (!preferred_zone) {
> put_mems_allowed();
> return NULL;
As previously mentioned, I didn't want to affect the current behavior of
mempolicies when they pass their own nodemask into the page allocator that
may be a subset of the set of allowed nodes; in that case, the statistics
are probably actually important and we can defer resetting preferred_zone
to the slowpath where we know its a __GFP_WAIT allocation instead of the
first try in the fastpath.
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