linux-kernel - Re: [PATCH v2 3/6] mm, page_alloc: pass preferred nid instead of zonelist to allocator

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Message-ID: <c748a22c-9a94-52cb-2247-afc281cc5d78@suse.cz>
Date:   Thu, 18 May 2017 12:25:03 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Christoph Lameter <cl@...ux.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, Li Zefan <lizefan@...wei.com>,
        Michal Hocko <mhocko@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        David Rientjes <rientjes@...gle.com>,
        Hugh Dickins <hughd@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dimitri Sivanich <sivanich@....com>
Subject: Re: [PATCH v2 3/6] mm, page_alloc: pass preferred nid instead of
 zonelist to allocator

On 05/17/2017 05:19 PM, Christoph Lameter wrote:
> On Wed, 17 May 2017, Vlastimil Babka wrote:
> 
>>  struct page *
>> -__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
>> -		       struct zonelist *zonelist, nodemask_t *nodemask);
>> +__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
>> +							nodemask_t *nodemask);
>>
>>  static inline struct page *
>> -__alloc_pages(gfp_t gfp_mask, unsigned int order,
>> -		struct zonelist *zonelist)
>> +__alloc_pages(gfp_t gfp_mask, unsigned int order, int preferred_nid)
>>  {
>> -	return __alloc_pages_nodemask(gfp_mask, order, zonelist, NULL);
>> +	return __alloc_pages_nodemask(gfp_mask, order, preferred_nid, NULL);
>>  }
> 
> Maybe use nid instead of preferred_nid like in __alloc_pages? Otherwise
> there may be confusion with the MPOL_PREFER policy.

I'll think about that.

>> @@ -1963,8 +1960,8 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
>>  {
>>  	struct mempolicy *pol;
>>  	struct page *page;
>> +	int preferred_nid;
>>  	unsigned int cpuset_mems_cookie;
>> -	struct zonelist *zl;
>>  	nodemask_t *nmask;
> 
> Same here.
> 
>> @@ -4012,8 +4012,8 @@ static inline void finalise_ac(gfp_t gfp_mask,
>>   * This is the 'heart' of the zoned buddy allocator.
>>   */
>>  struct page *
>> -__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
>> -			struct zonelist *zonelist, nodemask_t *nodemask)
>> +__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
>> +							nodemask_t *nodemask)
>>  {
> 
> and here
> 
> This looks clean to me. Still feel a bit uneasy about this since I do
> remember that we had a reason to use zonelists instead of nodes back then
> but cannot remember what that reason was....

My history digging showed me that mempolicies used to have a custom
zonelist attached, not nodemask. So I supposed that's why.

> CCing Dimitri at SGI. This may break a lot of legacy SGIapps. If you read
> this Dimitri then please review this patchset and the discussions around
> it.

Break how? This shouldn't break any apps AFAICS, just out-of-tree kernel
patches/modules as usual when APIs change.

> Reviewed-by: Christoph Lameter <cl@...ux.com>

Thanks!