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Date: Thu, 15 Feb 2018 11:59:20 -0500
From: Pavel Tatashin <pasha.tatashin@...cle.com>
To: steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
akpm@...ux-foundation.org, mgorman@...hsingularity.net,
mhocko@...e.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
gregkh@...uxfoundation.org, vbabka@...e.cz,
bharata@...ux.vnet.ibm.com, tglx@...utronix.de, mingo@...hat.com,
hpa@...or.com, x86@...nel.org, dan.j.williams@...el.com,
kirill.shutemov@...ux.intel.com, bhe@...hat.com
Subject: [v4 6/6] mm/memory_hotplug: optimize memory hotplug
During memory hotplugging we traverse struct pages three times:
1. memset(0) in sparse_add_one_section()
2. loop in __add_section() to set do: set_page_node(page, nid); and
SetPageReserved(page);
3. loop in memmap_init_zone() to call __init_single_pfn()
This patch remove the first two loops, and leaves only loop 3. All struct
pages are initialized in one place, the same as it is done during boot.
The benefits:
- We improve the memory hotplug performance because we are not evicting
cache several times and also reduce loop branching overheads.
- Remove condition from hotpath in __init_single_pfn(), that was added in
order to fix the problem that was reported by Bharata in the above email
thread, thus also improve the performance during normal boot.
- Make memory hotplug more similar to boot memory initialization path
because we zero and initialize struct pages only in one function.
- Simplifies memory hotplug strut page initialization code, and thus
enables future improvements, such as multi-threading the initialization
of struct pages in order to improve the hotplug performance even further
on larger machines.
Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
---
mm/memory_hotplug.c | 21 ++++++---------------
mm/page_alloc.c | 28 ++++++++++------------------
mm/sparse.c | 9 ++++++++-
3 files changed, 24 insertions(+), 34 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 565048f496f7..ee04dae21f0c 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -250,7 +250,7 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
struct vmem_altmap *altmap, bool want_memblock)
{
int ret;
- int i;
+ struct page *page;
if (pfn_valid(phys_start_pfn))
return -EEXIST;
@@ -260,21 +260,12 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
return ret;
/*
- * Make all the pages reserved so that nobody will stumble over half
- * initialized state.
- * FIXME: We also have to associate it with a node because page_to_nid
- * relies on having page with the proper node.
+ * The first page in every section holds node id, this is because we
+ * will need it in online_pages().
*/
- for (i = 0; i < PAGES_PER_SECTION; i++) {
- unsigned long pfn = phys_start_pfn + i;
- struct page *page;
- if (!pfn_valid(pfn))
- continue;
-
- page = pfn_to_page(pfn);
- set_page_node(page, nid);
- SetPageReserved(page);
- }
+ page = pfn_to_page(phys_start_pfn);
+ mm_zero_struct_page(page);
+ set_page_node(page, nid);
if (!want_memblock)
return 0;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 81e18ceef579..2667b35fca41 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1177,10 +1177,9 @@ static void free_one_page(struct zone *zone,
}
static void __meminit __init_single_page(struct page *page, unsigned long pfn,
- unsigned long zone, int nid, bool zero)
+ unsigned long zone, int nid)
{
- if (zero)
- mm_zero_struct_page(page);
+ mm_zero_struct_page(page);
set_page_links(page, zone, nid, pfn);
init_page_count(page);
page_mapcount_reset(page);
@@ -1194,12 +1193,6 @@ static void __meminit __init_single_page(struct page *page, unsigned long pfn,
#endif
}
-static void __meminit __init_single_pfn(unsigned long pfn, unsigned long zone,
- int nid, bool zero)
-{
- return __init_single_page(pfn_to_page(pfn), pfn, zone, nid, zero);
-}
-
#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
static void __meminit init_reserved_page(unsigned long pfn)
{
@@ -1218,7 +1211,7 @@ static void __meminit init_reserved_page(unsigned long pfn)
if (pfn >= zone->zone_start_pfn && pfn < zone_end_pfn(zone))
break;
}
- __init_single_pfn(pfn, zid, nid, true);
+ __init_single_page(pfn_to_page(pfn), pfn, zid, nid);
}
#else
static inline void init_reserved_page(unsigned long pfn)
@@ -1535,7 +1528,7 @@ static unsigned long __init deferred_init_pages(int nid, int zid,
} else {
page++;
}
- __init_single_page(page, pfn, zid, nid, true);
+ __init_single_page(page, pfn, zid, nid);
nr_pages++;
}
return (nr_pages);
@@ -5328,6 +5321,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
pg_data_t *pgdat = NODE_DATA(nid);
unsigned long pfn;
unsigned long nr_initialised = 0;
+ struct page *page;
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
struct memblock_region *r = NULL, *tmp;
#endif
@@ -5389,6 +5383,11 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
#endif
not_early:
+ page = pfn_to_page(pfn);
+ __init_single_page(page, pfn, zone, nid);
+ if (context == MEMMAP_HOTPLUG)
+ SetPageReserved(page);
+
/*
* Mark the block movable so that blocks are reserved for
* movable at startup. This will force kernel allocations
@@ -5405,15 +5404,8 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
* because this is done early in sparse_add_one_section
*/
if (!(pfn & (pageblock_nr_pages - 1))) {
- struct page *page = pfn_to_page(pfn);
-
- __init_single_page(page, pfn, zone, nid,
- context != MEMMAP_HOTPLUG);
set_pageblock_migratetype(page, MIGRATE_MOVABLE);
cond_resched();
- } else {
- __init_single_pfn(pfn, zone, nid,
- context != MEMMAP_HOTPLUG);
}
}
}
diff --git a/mm/sparse.c b/mm/sparse.c
index 7af5e7a92528..eb72de54089c 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -816,7 +816,14 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
goto out;
}
- memset(memmap, 0, sizeof(struct page) * PAGES_PER_SECTION);
+#ifdef CONFIG_DEBUG_VM
+ /*
+ * poison uninitialized struct pages in order to catch invalid flags
+ * combinations.
+ */
+ memset(memmap, PAGE_POISON_PATTERN,
+ sizeof(struct page) * PAGES_PER_SECTION);
+#endif
section_mark_present(ms);
--
2.16.1
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