Re: [PATCH v6 4/6] mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY

[Feng Tang]

Mike,

On Wed, Jul 21, 2021 at 01:49:15PM -0700, Mike Kravetz wrote:
> On 7/12/21 1:09 AM, Feng Tang wrote:
> > From: Ben Widawsky <ben.widawsky@xxxxxxxxx>
> > 
> > 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@xxxxxxxxx
> > Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
> > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
> > Co-developed-by: Feng Tang <feng.tang@xxxxxxxxx>
> > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
> > ---
> >  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?

Thanks for the suggestion, will remove it. 

> > +
> > +		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@xxxxxxxxxx>

Thanks!



Andrew,

I have to ask for your help again to fold this to the 4/6 patch, thanks!

- Feng

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