linux-kernel - Re: [PATCH 2/2] mm: hugetlb: Use node interface of cma

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Message-ID: <20200327151339.GF10449@dhcp22.suse.cz>
Date:   Fri, 27 Mar 2020 16:13:39 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Roman Gushchin <guro@...com>
Cc:     Aslan Bakirov <aslan@...com>, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-team@...com, riel@...riel.com, hannes@...xchg.org
Subject: Re: [PATCH 2/2] mm: hugetlb: Use node interface of cma

On Fri 27-03-20 07:41:55, Roman Gushchin wrote:
> On Fri, Mar 27, 2020 at 09:06:10AM +0100, Michal Hocko wrote:
> > On Thu 26-03-20 14:27:18, Aslan Bakirov wrote:
> > > With introduction of numa node interface for CMA, this patch is for using that
> > > interface for allocating memory on numa nodes if NUMA is configured.
> > > This will be more efficient  and cleaner because first, instead of iterating
> > > mem range of each numa node, cma_declare_contigueous_nid() will do
> > > its own address finding if we pass 0 for  both min_pfn and max_pfn,
> > > second, it can also handle caseswhere NUMA is not configured
> > > by passing NUMA_NO_NODE as an argument.
> > > 
> > > In addition, checking if desired size of memory is available or not,
> > > is happening in cma_declare_contiguous_nid()  because base and
> > > limit will be determined there, since 0(any) for  base and
> > > 0(any) for limit is passed as argument to the function.
> > 
> > This looks much better than the original patch. Can we simply squash
> > your and Roman's patch in the mmotm tree and post it for the review in
> > one piece? It would be slightly easier to review that way.
> 
> I'm glad you liked it! I agree, it's much nicer now, thanks to Aslan!
> 
> I think it's simpler to keep it as a separate patch, because there was
> already a fix by Randy Dunlap on top of my original version.

Why would be squashing all those into a single one be a problem. I will
not insist of course but I would much rather see a single patch which is
easy to review and doesn't contain any intermediate hacks to prevent
from compile time issues than 3 patches with the last one removing hacks
and a large part of the implementation. You can easily record the
multiple authors can be easily recorded in the s-o-b chain.

> > > Signed-off-by: Aslan Bakirov <aslan@...com>
> 
> Acked-by: Roman Gushchin <guro@...com>
> 
> Thanks!
> 
> > 
> > Thanks!
> > 
> > > ---
> > >  mm/hugetlb.c | 40 +++++++++++-----------------------------
> > >  1 file changed, 11 insertions(+), 29 deletions(-)
> > > 
> > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > > index b9f0c903c4cf..62989220c4ff 100644
> > > --- a/mm/hugetlb.c
> > > +++ b/mm/hugetlb.c
> > > @@ -5573,42 +5573,24 @@ void __init hugetlb_cma_reserve(int order)
> > >  
> > >  	reserved = 0;
> > >  	for_each_node_state(nid, N_ONLINE) {
> > > -		unsigned long min_pfn = 0, max_pfn = 0;
> > >  		int res;
> > > -#ifdef CONFIG_NUMA
> > > -		unsigned long start_pfn, end_pfn;
> > > -		int i;
> > >  
> > > -		for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
> > > -			if (!min_pfn)
> > > -				min_pfn = start_pfn;
> > > -			max_pfn = end_pfn;
> > > -		}
> > > -#else
> > > -		min_pfn = min_low_pfn;
> > > -		max_pfn = max_low_pfn;
> > > -#endif
> > >  		size = min(per_node, hugetlb_cma_size - reserved);
> > >  		size = round_up(size, PAGE_SIZE << order);
> > > -
> > > -		if (size > ((max_pfn - min_pfn) << PAGE_SHIFT) / 2) {
> > > -			pr_warn("hugetlb_cma: cma_area is too big, please try less than %lu MiB\n",
> > > -				round_down(((max_pfn - min_pfn) << PAGE_SHIFT) *
> > > -					   nr_online_nodes / 2 / SZ_1M,
> > > -					   PAGE_SIZE << order));
> > > -			break;
> > > -		}
> > > -
> > > -		res = cma_declare_contiguous(PFN_PHYS(min_pfn), size,
> > > -					     PFN_PHYS(max_pfn),
> > > +		
> > > +		
> > > +#ifndef CONFIG_NUMA
> > > +		nid = NUMA_NO_NODE
> > > +#endif		
> > > +		res = cma_declare_contiguous_nid(0, size,
> > > +					     0, 
> > >  					     PAGE_SIZE << order,
> > >  					     0, false,
> > > -					     "hugetlb", &hugetlb_cma[nid]);
> > > +					     "hugetlb", &hugetlb_cma[nid], nid);		
> > > +
> > >  		if (res) {
> > > -			phys_addr_t begpa = PFN_PHYS(min_pfn);
> > > -			phys_addr_t endpa = PFN_PHYS(max_pfn);
> > > -			pr_warn("%s: reservation failed: err %d, node %d, [%pap, %pap)\n",
> > > -				__func__, res, nid, &begpa, &endpa);
> > > +			pr_warn("%s: reservation failed: err %d, node %d\n",
> > > +				__func__, res, nid);
> > >  			break;
> > >  		}
> > >  
> > > -- 
> > > 2.17.1
> > 
> > -- 
> > Michal Hocko
> > SUSE Labs

-- 
Michal Hocko
SUSE Labs