Re: [patch] mm: fix deferred congestion timeout if preferred zone is not allowed

[David Rientjes <rientjes@google.com>]

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.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>