linux-kernel - Re: [PATCH v3 1/1] mm: page_alloc: skip over regions of invalid pfns on UMA

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Date:   Mon, 12 Feb 2018 16:03:14 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Eugeniu Rosca <erosca@...adit-jv.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Steven Sistare <steven.sistare@...cle.com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Gioh Kim <gi-oh.kim@...fitbricks.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Miles Chen <miles.chen@...iatek.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hartley <james.hartley@...s.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 1/1] mm: page_alloc: skip over regions of invalid pfns
 on UMA

On Sat 03-02-18 13:24:22, Eugeniu Rosca wrote:
[...]
> That said, I really hope this won't be the last comment in the thread
> and appropriate suggestions will come on how to go forward.

Just to make sure we are on the same page. I was suggesting the
following. The patch is slightly larger just because I move
memblock_next_valid_pfn around which I find better than sprinkling
ifdefs around. Please note I haven't tried to compile test this.

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 8be5077efb5f..0d3cb4c70858 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -187,7 +187,6 @@ int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn,
 			    unsigned long  *end_pfn);
 void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
 			  unsigned long *out_end_pfn, int *out_nid);
-unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn);
 
 /**
  * for_each_mem_pfn_range - early memory pfn range iterator
@@ -204,6 +203,8 @@ unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn);
 	     i >= 0; __next_mem_pfn_range(&i, nid, p_start, p_end, p_nid))
 #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
 
+unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn);
+
 /**
  * for_each_free_mem_range - iterate through free memblock areas
  * @i: u64 used as loop variable
diff --git a/mm/memblock.c b/mm/memblock.c
index 5a9ca2a1751b..8a627d4fa5b2 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1101,34 +1101,6 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
 		*out_nid = r->nid;
 }
 
-unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
-						      unsigned long max_pfn)
-{
-	struct memblock_type *type = &memblock.memory;
-	unsigned int right = type->cnt;
-	unsigned int mid, left = 0;
-	phys_addr_t addr = PFN_PHYS(pfn + 1);
-
-	do {
-		mid = (right + left) / 2;
-
-		if (addr < type->regions[mid].base)
-			right = mid;
-		else if (addr >= (type->regions[mid].base +
-				  type->regions[mid].size))
-			left = mid + 1;
-		else {
-			/* addr is within the region, so pfn + 1 is valid */
-			return min(pfn + 1, max_pfn);
-		}
-	} while (left < right);
-
-	if (right == type->cnt)
-		return max_pfn;
-	else
-		return min(PHYS_PFN(type->regions[right].base), max_pfn);
-}
-
 /**
  * memblock_set_node - set node ID on memblock regions
  * @base: base of area to set node ID for
@@ -1160,6 +1132,34 @@ int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,
 }
 #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
 
+unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
+						      unsigned long max_pfn)
+{
+	struct memblock_type *type = &memblock.memory;
+	unsigned int right = type->cnt;
+	unsigned int mid, left = 0;
+	phys_addr_t addr = PFN_PHYS(pfn + 1);
+
+	do {
+		mid = (right + left) / 2;
+
+		if (addr < type->regions[mid].base)
+			right = mid;
+		else if (addr >= (type->regions[mid].base +
+				  type->regions[mid].size))
+			left = mid + 1;
+		else {
+			/* addr is within the region, so pfn + 1 is valid */
+			return min(pfn + 1, max_pfn);
+		}
+	} while (left < right);
+
+	if (right == type->cnt)
+		return max_pfn;
+	else
+		return min(PHYS_PFN(type->regions[right].base), max_pfn);
+}
+
 static phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
 					phys_addr_t align, phys_addr_t start,
 					phys_addr_t end, int nid, ulong flags)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e2b42f603b1a..b7968fd5736f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5352,14 +5352,13 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 			goto not_early;
 
 		if (!early_pfn_valid(pfn)) {
-#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
 			/*
 			 * Skip to the pfn preceding the next valid one (or
 			 * end_pfn), such that we hit a valid pfn (or end_pfn)
 			 * on our next iteration of the loop.
 			 */
-			pfn = memblock_next_valid_pfn(pfn, end_pfn) - 1;
-#endif
+			if IS_ENABLED(HAVE_MEMBLOCK)
+				pfn = memblock_next_valid_pfn(pfn, end_pfn) - 1;
 			continue;
 		}
 		if (!early_pfn_in_nid(pfn, nid))
-- 
Michal Hocko
SUSE Labs