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Date:   Thu, 28 Jun 2018 13:19:54 +0200
From:   Oscar Salvador <osalvador@techadventures.net>
To:     Baoquan He <bhe@redhat.com>
Cc:     linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        dave.hansen@intel.com, pagupta@redhat.com,
        Pavel Tatashin <pasha.tatashin@oracle.com>, linux-mm@kvack.org,
        kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v6 2/5] mm/sparsemem: Defer the ms->section_mem_map
 clearing
Message-ID: <20180628111954.GA12956@techadventures.net>
References: <20180628062857.29658-1-bhe@redhat.com>
 <20180628062857.29658-3-bhe@redhat.com>
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On Thu, Jun 28, 2018 at 02:28:54PM +0800, Baoquan He wrote:
> In sparse_init(), if CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER=y, system
> will allocate one continuous memory chunk for mem maps on one node and
> populate the relevant page tables to map memory section one by one. If
> fail to populate for a certain mem section, print warning and its
> ->section_mem_map will be cleared to cancel the marking of being present.
> Like this, the number of mem sections marked as present could become
> less during sparse_init() execution.
> 
> Here just defer the ms->section_mem_map clearing if failed to populate
> its page tables until the last for_each_present_section_nr() loop. This
> is in preparation for later optimizing the mem map allocation.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> Reviewed-by: Pavel Tatashin <pasha.tatashin@oracle.com>

Looks good to me.

Reviewed-by: Oscar Salvador <osalvador@suse.de>

> ---
>  mm/sparse-vmemmap.c |  4 ----
>  mm/sparse.c         | 15 ++++++++-------
>  2 files changed, 8 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index bd0276d5f66b..68bb65b2d34d 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -292,18 +292,14 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
>  	}
>  
>  	for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> -		struct mem_section *ms;
> -
>  		if (!present_section_nr(pnum))
>  			continue;
>  
>  		map_map[pnum] = sparse_mem_map_populate(pnum, nodeid, NULL);
>  		if (map_map[pnum])
>  			continue;
> -		ms = __nr_to_section(pnum);
>  		pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
>  		       __func__);
> -		ms->section_mem_map = 0;
>  	}
>  
>  	if (vmemmap_buf_start) {
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 6314303130b0..6a706093307d 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -441,17 +441,13 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
>  
>  	/* fallback */
>  	for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
> -		struct mem_section *ms;
> -
>  		if (!present_section_nr(pnum))
>  			continue;
>  		map_map[pnum] = sparse_mem_map_populate(pnum, nodeid, NULL);
>  		if (map_map[pnum])
>  			continue;
> -		ms = __nr_to_section(pnum);
>  		pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
>  		       __func__);
> -		ms->section_mem_map = 0;
>  	}
>  }
>  #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
> @@ -479,7 +475,6 @@ static struct page __init *sparse_early_mem_map_alloc(unsigned long pnum)
>  
>  	pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
>  	       __func__);
> -	ms->section_mem_map = 0;
>  	return NULL;
>  }
>  #endif
> @@ -583,17 +578,23 @@ void __init sparse_init(void)
>  #endif
>  
>  	for_each_present_section_nr(0, pnum) {
> +		struct mem_section *ms;
> +		ms = __nr_to_section(pnum);
>  		usemap = usemap_map[pnum];
> -		if (!usemap)
> +		if (!usemap) {
> +			ms->section_mem_map = 0;
>  			continue;
> +		}
>  
>  #ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
>  		map = map_map[pnum];
>  #else
>  		map = sparse_early_mem_map_alloc(pnum);
>  #endif
> -		if (!map)
> +		if (!map) {
> +			ms->section_mem_map = 0;
>  			continue;
> +		}
>  
>  		sparse_init_one_section(__nr_to_section(pnum), pnum, map,
>  								usemap);
> -- 
> 2.13.6
> 

-- 
Oscar Salvador
SUSE L3