linux-kernel - Re: [PATCH] mm, mempolicy: clean up __GFP_THISNODE confusion in policy

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Message-ID: <c8f66d33-f2e9-c29d-6cfd-9eebb4832ebe@suse.cz>
Date:   Fri, 21 Oct 2016 14:08:19 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mel Gorman <mgorman@...e.de>, David Rientjes <rientjes@...gle.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] mm, mempolicy: clean up __GFP_THISNODE confusion in
 policy_zonelist

On 10/21/2016 01:34 PM, Aneesh Kumar K.V wrote:
> Michal Hocko <mhocko@...nel.org> writes:
>>
>
> For both MPOL_PREFERED and MPOL_INTERLEAVE we pick the zone list from
> the node other than the current running node. Why don't we do that for
> MPOL_BIND ?ie, if the current node is not part of the policy node mask
> why are we not picking the first node from the policy node mask for
> MPOL_BIND ?

For MPOL_PREFERED and MPOL_INTERLEAVE we got some explicit preference of nodes, 
so it makes sense that the nodes in the zonelist we pick are ordered by the 
distance from that node, regardless of current node.

For MPOL_BIND, we don't have preferences but restrictions. If the current cpu is 
from a node within the restriction, then great. If it's not, finding a node 
according to distance from current cpu is probably less arbitrary than by 
distance from the node that happens to have the lowest id in the node mask?

> -aneesh
>
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