linux-kernel - Re: [PATCH v6 4/6] mm/hugetlb: add support for mempolicy MPOL_PREFERRED

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Message-ID: <7cdf88d8-9eea-5547-ee77-7d46829bf2dd@oracle.com>
Date:   Wed, 21 Jul 2021 13:49:15 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Feng Tang <feng.tang@...el.com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andi Kleen <ak@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>, ying.huang@...el.com
Subject: Re: [PATCH v6 4/6] mm/hugetlb: add support for mempolicy
 MPOL_PREFERRED_MANY

On 7/12/21 1:09 AM, Feng Tang wrote:
> From: Ben Widawsky <ben.widawsky@...el.com>
> 
> Implement the missing huge page allocation functionality while obeying
> the preferred node semantics. This is similar to the implementation
> for general page allocation, as it uses a fallback mechanism to try
> multiple preferred nodes first, and then all other nodes.
> 
> [Thanks to 0day bot for caching the missing #ifdef CONFIG_NUMA issue]
> 
> Link: https://lore.kernel.org/r/20200630212517.308045-12-ben.widawsky@intel.com
> Suggested-by: Michal Hocko <mhocko@...e.com>
> Signed-off-by: Ben Widawsky <ben.widawsky@...el.com>
> Co-developed-by: Feng Tang <feng.tang@...el.com>
> Signed-off-by: Feng Tang <feng.tang@...el.com>
> ---
>  mm/hugetlb.c   | 25 +++++++++++++++++++++++++
>  mm/mempolicy.c |  3 ++-
>  2 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 924553aa8f78..3e84508c1b8c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1164,7 +1164,18 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
>  
>  	gfp_mask = htlb_alloc_mask(h);
>  	nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
> +#ifdef CONFIG_NUMA
> +	if (mpol->mode == MPOL_PREFERRED_MANY) {
> +		page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);
> +		if (page)
> +			goto check_reserve;
> +		/* Fallback to all nodes */
> +		nodemask = NULL;
> +	}
> +#endif
>  	page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);
> +
> +check_reserve:
>  	if (page && !avoid_reserve && vma_has_reserves(vma, chg)) {
>  		SetHPageRestoreReserve(page);
>  		h->resv_huge_pages--;
> @@ -2095,6 +2106,20 @@ struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
>  	nodemask_t *nodemask;
>  
>  	nid = huge_node(vma, addr, gfp_mask, &mpol, &nodemask);
> +#ifdef CONFIG_NUMA
> +	if (mpol->mode == MPOL_PREFERRED_MANY) {
> +		gfp_t gfp = (gfp_mask | __GFP_NOWARN) & ~__GFP_DIRECT_RECLAIM;

I believe __GFP_NOWARN will be added later in alloc_buddy_huge_page, so
no need to add here?

> +
> +		page = alloc_surplus_huge_page(h, gfp, nid, nodemask);
> +		if (page) {
> +			mpol_cond_put(mpol);
> +			return page;
> +		}
> +
> +		/* Fallback to all nodes */
> +		nodemask = NULL;
> +	}
> +#endif
>  	page = alloc_surplus_huge_page(h, gfp_mask, nid, nodemask);
>  	mpol_cond_put(mpol);
>  
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 9dce67fc9bb6..93f8789758a7 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2054,7 +2054,8 @@ int huge_node(struct vm_area_struct *vma, unsigned long addr, gfp_t gfp_flags,
>  					huge_page_shift(hstate_vma(vma)));
>  	} else {
>  		nid = policy_node(gfp_flags, *mpol, numa_node_id());
> -		if ((*mpol)->mode == MPOL_BIND)
> +		if ((*mpol)->mode == MPOL_BIND ||
> +		    (*mpol)->mode == MPOL_PREFERRED_MANY)
>  			*nodemask = &(*mpol)->nodes;
>  	}
>  	return nid;
> 

Other than the one nit above,

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>

-- 
Mike Kravetz