From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm: remove return value from init_currently_empty_zone
Patch series "mm: make movable onlining suck less", v4.
Movable onlining is a real hack with many downsides - mainly
reintroduction of lowmem/highmem issues we used to have on 32b systems -
but it is the only way to make the memory hotremove more reliable which is
something that people are asking for.
The current semantic of memory movable onlinening is really cumbersome,
however. The main reason for this is that the udev driven approach is
basically unusable because udev races with the memory probing while only
the last memory block or the one adjacent to the existing zone_movable are
allowed to be onlined movable. In short the criterion for the successful
online_movable changes under udev's feet. A reliable udev approach would
require a 2 phase approach where the first successful movable online would
have to check all the previous blocks and online them in descending order.
This is hard to be considered sane.
This patchset aims at making the onlining semantic more usable. First of
all it allows to online memory movable as long as it doesn't clash with
the existing ZONE_NORMAL. That means that ZONE_NORMAL and ZONE_MOVABLE
cannot overlap. Currently I preserve the original ordering semantic so
the zone always precedes the movable zone but I have plans to remove this
restriction in future because it is not really necessary.
First 3 patches are cleanups which should be ready to be merged right
away (unless I have missed something subtle of course).
Patch 4 deals with ZONE_DEVICE dependencies down the __add_pages path.
Patch 5 deals with implicit assumptions of register_one_node on pgdat
initialization.
Patches 6-10 deal with offline holes in the zone for pfn walkers. I
hope I got all of them right but people familiar with compaction should
double check this.
Patch 11 is the core of the change. In order to make it easier to review
I have tried it to be as minimalistic as possible and the large code
removal is moved to patch 14.
Patch 12 is a trivial follow up cleanup. Patch 13 fixes sparse warnings
and finally patch 14 removes the unused code.
I have tested the patches in kvm:
# qemu-system-x86_64 -enable-kvm -monitor pty -m 2G,slots=4,maxmem=4G -numa node,mem=1G -numa node,mem=1G ...
and then probed the additional memory by
(qemu) object_add memory-backend-ram,id=mem1,size=1G
(qemu) device_add pc-dimm,id=dimm1,memdev=mem1
Then I have used this simple script to probe the memory block by hand
# cat probe_memblock.sh
#!/bin/sh
BLOCK_NR=$1
# echo $((0x100000000+$BLOCK_NR*(128<<20))) > /sys/devices/system/memory/probe
# for i in $(seq 10); do sh probe_memblock.sh $i; done
# grep . /sys/devices/system/memory/memory3?/valid_zones 2>/dev/null
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Normal Movable
/sys/devices/system/memory/memory35/valid_zones:Normal Movable
/sys/devices/system/memory/memory36/valid_zones:Normal Movable
/sys/devices/system/memory/memory37/valid_zones:Normal Movable
/sys/devices/system/memory/memory38/valid_zones:Normal Movable
/sys/devices/system/memory/memory39/valid_zones:Normal Movable
The main difference to the original implementation is that all new
memblocks can be both online_kernel and online_movable initially
because there is no clash obviously. For the comparison the original
implementation would have
/sys/devices/system/memory/memory33/valid_zones:Normal
/sys/devices/system/memory/memory34/valid_zones:Normal
/sys/devices/system/memory/memory35/valid_zones:Normal
/sys/devices/system/memory/memory36/valid_zones:Normal
/sys/devices/system/memory/memory37/valid_zones:Normal
/sys/devices/system/memory/memory38/valid_zones:Normal
/sys/devices/system/memory/memory39/valid_zones:Normal Movable
Now
# echo online_movable > /sys/devices/system/memory/memory34/state
# grep . /sys/devices/system/memory/memory3?/valid_zones 2>/dev/null
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable
/sys/devices/system/memory/memory35/valid_zones:Movable
/sys/devices/system/memory/memory36/valid_zones:Movable
/sys/devices/system/memory/memory37/valid_zones:Movable
/sys/devices/system/memory/memory38/valid_zones:Movable
/sys/devices/system/memory/memory39/valid_zones:Movable
Block 33 can still be online both kernel and movable while all
the remaining can be only movable.
/proc/zonelist says
Node 0, zone Normal
pages free 0
min 0
low 0
high 0
spanned 0
present 0
--
Node 0, zone Movable
pages free 32753
min 85
low 117
high 149
spanned 32768
present 32768
A new memblock at a lower address will result in a new memblock (32)
which will still allow both Normal and Movable.
# sh probe_memblock.sh 0
# grep . /sys/devices/system/memory/memory3[2-5]/valid_zones 2>/dev/null
/sys/devices/system/memory/memory32/valid_zones:Normal Movable
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable
/sys/devices/system/memory/memory35/valid_zones:Movable
and online_kernel will convert it to the zone normal properly
while 33 can be still onlined both ways.
# echo online_kernel > /sys/devices/system/memory/memory32/state
# grep . /sys/devices/system/memory/memory3[2-5]/valid_zones 2>/dev/null
/sys/devices/system/memory/memory32/valid_zones:Normal
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable
/sys/devices/system/memory/memory35/valid_zones:Movable
/proc/zoneinfo will now tell
Node 0, zone Normal
pages free 65441
min 165
low 230
high 295
spanned 65536
present 65536
--
Node 0, zone Movable
pages free 32740
min 82
low 114
high 146
spanned 32768
present 32768
so both zones have one memblock spanned and present.
Onlining 39 should associate this block to the movable zone
# echo online > /sys/devices/system/memory/memory39/state
/proc/zoneinfo will now tell
Node 0, zone Normal
pages free 32765
min 80
low 112
high 144
spanned 32768
present 32768
--
Node 0, zone Movable
pages free 65501
min 160
low 225
high 290
spanned 196608
present 65536
so we will have a movable zone which spans 6 memblocks, 2 present and 4
representing a hole.
Offlining both movable blocks will lead to the zone with no present
pages which is the expected behavior I believe.
# echo offline > /sys/devices/system/memory/memory39/state
# echo offline > /sys/devices/system/memory/memory34/state
# grep -A6 "Movable\|Normal" /proc/zoneinfo
Node 0, zone Normal
pages free 32735
min 90
low 122
high 154
spanned 32768
present 32768
--
Node 0, zone Movable
pages free 0
min 0
low 0
high 0
spanned 196608
present 0
As a bonus we will get a nice cleanup in the memory hotplug codebase.
This patch (of 16):
init_currently_empty_zone doesn't have any error to return yet it is still
an int and callers try to be defensive and try to handle potential error.
Remove this nonsense and simplify all callers.
This patch shouldn't have any visible effect
Link: http://lkml.kernel.org/r/20170515085827.16474-2-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Acked-by: Balbir Singh <bsingharora@xxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Igor Mammedov <imammedo@xxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: Joonsoo Kim <js1304@xxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
Cc: Tobias Regnery <tobias.regnery@xxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 2 +-
mm/memory_hotplug.c | 23 +++++------------------
mm/page_alloc.c | 8 ++------
3 files changed, 8 insertions(+), 25 deletions(-)
diff -puN include/linux/mmzone.h~mm-remove-return-value-from-init_currently_empty_zone include/linux/mmzone.h
--- a/include/linux/mmzone.h~mm-remove-return-value-from-init_currently_empty_zone
+++ a/include/linux/mmzone.h
@@ -772,7 +772,7 @@ enum memmap_context {
MEMMAP_EARLY,
MEMMAP_HOTPLUG,
};
-extern int init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,
+extern void init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,
unsigned long size);
extern void lruvec_init(struct lruvec *lruvec);
diff -puN mm/memory_hotplug.c~mm-remove-return-value-from-init_currently_empty_zone mm/memory_hotplug.c
--- a/mm/memory_hotplug.c~mm-remove-return-value-from-init_currently_empty_zone
+++ a/mm/memory_hotplug.c
@@ -348,27 +348,20 @@ static void fix_zone_id(struct zone *zon
set_page_links(pfn_to_page(pfn), zid, nid, pfn);
}
-/* Can fail with -ENOMEM from allocating a wait table with vmalloc() or
- * alloc_bootmem_node_nopanic()/memblock_virt_alloc_node_nopanic() */
-static int __ref ensure_zone_is_initialized(struct zone *zone,
+static void __ref ensure_zone_is_initialized(struct zone *zone,
unsigned long start_pfn, unsigned long num_pages)
{
if (!zone_is_initialized(zone))
- return init_currently_empty_zone(zone, start_pfn, num_pages);
-
- return 0;
+ init_currently_empty_zone(zone, start_pfn, num_pages);
}
static int __meminit move_pfn_range_left(struct zone *z1, struct zone *z2,
unsigned long start_pfn, unsigned long end_pfn)
{
- int ret;
unsigned long flags;
unsigned long z1_start_pfn;
- ret = ensure_zone_is_initialized(z1, start_pfn, end_pfn - start_pfn);
- if (ret)
- return ret;
+ ensure_zone_is_initialized(z1, start_pfn, end_pfn - start_pfn);
pgdat_resize_lock(z1->zone_pgdat, &flags);
@@ -404,13 +397,10 @@ out_fail:
static int __meminit move_pfn_range_right(struct zone *z1, struct zone *z2,
unsigned long start_pfn, unsigned long end_pfn)
{
- int ret;
unsigned long flags;
unsigned long z2_end_pfn;
- ret = ensure_zone_is_initialized(z2, start_pfn, end_pfn - start_pfn);
- if (ret)
- return ret;
+ ensure_zone_is_initialized(z2, start_pfn, end_pfn - start_pfn);
pgdat_resize_lock(z1->zone_pgdat, &flags);
@@ -481,12 +471,9 @@ static int __meminit __add_zone(struct z
int nid = pgdat->node_id;
int zone_type;
unsigned long flags, pfn;
- int ret;
zone_type = zone - pgdat->node_zones;
- ret = ensure_zone_is_initialized(zone, phys_start_pfn, nr_pages);
- if (ret)
- return ret;
+ ensure_zone_is_initialized(zone, phys_start_pfn, nr_pages);
pgdat_resize_lock(zone->zone_pgdat, &flags);
grow_zone_span(zone, phys_start_pfn, phys_start_pfn + nr_pages);
diff -puN mm/page_alloc.c~mm-remove-return-value-from-init_currently_empty_zone mm/page_alloc.c
--- a/mm/page_alloc.c~mm-remove-return-value-from-init_currently_empty_zone
+++ a/mm/page_alloc.c
@@ -5528,7 +5528,7 @@ static __meminit void zone_pcp_init(stru
zone_batchsize(zone));
}
-int __meminit init_currently_empty_zone(struct zone *zone,
+void __meminit init_currently_empty_zone(struct zone *zone,
unsigned long zone_start_pfn,
unsigned long size)
{
@@ -5546,8 +5546,6 @@ int __meminit init_currently_empty_zone(
zone_init_free_lists(zone);
zone->initialized = 1;
-
- return 0;
}
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
@@ -6005,7 +6003,6 @@ static void __paginginit free_area_init_
{
enum zone_type j;
int nid = pgdat->node_id;
- int ret;
pgdat_resize_init(pgdat);
#ifdef CONFIG_NUMA_BALANCING
@@ -6087,8 +6084,7 @@ static void __paginginit free_area_init_
set_pageblock_order();
setup_usemap(pgdat, zone, zone_start_pfn, size);
- ret = init_currently_empty_zone(zone, zone_start_pfn, size);
- BUG_ON(ret);
+ init_currently_empty_zone(zone, zone_start_pfn, size);
memmap_init(size, nid, j, zone_start_pfn);
}
}
_
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