The patch titled
Subject: mm: get rid of zone_is_initialized
has been added to the -mm tree. Its filename is
mm-get-rid-of-zone_is_initialized.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-get-rid-of-zone_is_initialized.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-get-rid-of-zone_is_initialized.patch
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------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm: get rid of zone_is_initialized
Motivation: 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.
The series consists of 4 cleanup patches which should be ready to be
merged right away (unless I have missed something subtle of course).
Patch 5 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 6.
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 5):
There shouldn't be any reason to add initialized when we can tell the same
thing from checking whether there are any pages spanned to the zone.
Remove zone_is_initialized() and replace it by zone_is_empty which can be
used for the same set of tests.
This shouldn't have any visible effect.
Link: http://lkml.kernel.org/r/20170330115454.32154-2-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: "Luck, Tony" <tony.luck@xxxxxxxxx>
Cc: <slaoub@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
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: Ingo Molnar <mingo@xxxxxxx>
Cc: Joonsoo Kim <js1304@xxxxxxxxx>
Cc: Kani Toshimitsu <toshi.kani@xxxxxxx>
Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
Cc: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Cc: Yasuaki Ishimatsu <yasu.isimatu@xxxxxxxxx>
Cc: Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 11 +++++------
mm/memory_hotplug.c | 6 +++---
mm/page_alloc.c | 5 +----
3 files changed, 9 insertions(+), 13 deletions(-)
diff -puN include/linux/mmzone.h~mm-get-rid-of-zone_is_initialized include/linux/mmzone.h
--- a/include/linux/mmzone.h~mm-get-rid-of-zone_is_initialized
+++ a/include/linux/mmzone.h
@@ -442,8 +442,6 @@ struct zone {
seqlock_t span_seqlock;
#endif
- int initialized;
-
/* Write-intensive fields used from the page allocator */
ZONE_PADDING(_pad1_)
@@ -520,14 +518,15 @@ static inline bool zone_spans_pfn(const
return zone->zone_start_pfn <= pfn && pfn < zone_end_pfn(zone);
}
-static inline bool zone_is_initialized(struct zone *zone)
+static inline bool zone_is_empty(struct zone *zone)
{
- return zone->initialized;
+ return zone->spanned_pages == 0;
}
-static inline bool zone_is_empty(struct zone *zone)
+static inline bool zone_spans_range(const struct zone *zone, unsigned long start_pfn,
+ unsigned long nr_pages)
{
- return zone->spanned_pages == 0;
+ return zone->zone_start_pfn <= start_pfn && start_pfn + nr_pages < zone_end_pfn(zone);
}
/*
diff -puN mm/memory_hotplug.c~mm-get-rid-of-zone_is_initialized mm/memory_hotplug.c
--- a/mm/memory_hotplug.c~mm-get-rid-of-zone_is_initialized
+++ a/mm/memory_hotplug.c
@@ -353,7 +353,7 @@ static void fix_zone_id(struct zone *zon
static int __ref ensure_zone_is_initialized(struct zone *zone,
unsigned long start_pfn, unsigned long num_pages)
{
- if (!zone_is_initialized(zone))
+ if (zone_is_empty(zone))
return init_currently_empty_zone(zone, start_pfn, num_pages);
return 0;
@@ -1056,7 +1056,7 @@ bool zone_can_shift(unsigned long pfn, u
/* no zones in use between current zone and target */
for (i = idx + 1; i < target; i++)
- if (zone_is_initialized(zone - idx + i))
+ if (!zone_is_empty(zone - idx + i))
return false;
}
@@ -1067,7 +1067,7 @@ bool zone_can_shift(unsigned long pfn, u
/* no zones in use between current zone and target */
for (i = target + 1; i < idx; i++)
- if (zone_is_initialized(zone - idx + i))
+ if (!zone_is_empty(zone - idx + i))
return false;
}
diff -puN mm/page_alloc.c~mm-get-rid-of-zone_is_initialized mm/page_alloc.c
--- a/mm/page_alloc.c~mm-get-rid-of-zone_is_initialized
+++ a/mm/page_alloc.c
@@ -796,7 +796,7 @@ static inline void __free_one_page(struc
max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1);
- VM_BUG_ON(!zone_is_initialized(zone));
+ VM_BUG_ON(zone_is_empty(zone));
VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);
VM_BUG_ON(migratetype == -1);
@@ -5534,9 +5534,6 @@ int __meminit init_currently_empty_zone(
zone_start_pfn, (zone_start_pfn + size));
zone_init_free_lists(zone);
- zone->initialized = 1;
-
- return 0;
}
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
_
Patches currently in -mm which might be from mhocko@xxxxxxxx are
mm-move-mm_percpu_wq-initialization-earlier.patch
lockdep-allow-to-disable-reclaim-lockup-detection.patch
xfs-abstract-pf_fstrans-to-pf_memalloc_nofs.patch
mm-introduce-memalloc_nofs_saverestore-api.patch
xfs-use-memalloc_nofs_saverestore-instead-of-memalloc_noio.patch
jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context.patch
jbd2-make-the-whole-kjournald2-kthread-nofs-safe.patch
mm-move-pcp-and-lru-pcp-drainging-into-single-wq.patch
mm-get-rid-of-zone_is_initialized.patch
mm-tile-drop-arch_addremove_memory.patch
mm-remove-return-value-from-init_currently_empty_zone.patch
mm-memory_hotplug-use-node-instead-of-zone-in-can_online_high_movable.patch
mm-memory_hotplug-do-not-associate-hotadded-memory-to-zones-until-online.patch
mm-memory_hotplug-remove-unused-cruft-after-memory-hotplug-rework.patch
mm-introduce-kvalloc-helpers.patch
mm-support-__gfp_repeat-in-kvmalloc_node-for-32kb.patch
rhashtable-simplify-a-strange-allocation-pattern.patch
ila-simplify-a-strange-allocation-pattern.patch
xattr-zero-out-memory-copied-to-userspace-in-getxattr.patch
treewide-use-kvalloc-rather-than-opencoded-variants.patch
net-use-kvmalloc-with-__gfp_repeat-rather-than-open-coded-variant.patch
md-use-kvmalloc-rather-than-opencoded-variant.patch
bcache-use-kvmalloc.patch
mm-vmalloc-use-__gfp_highmem-implicitly.patch
--
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