linux_dsm_epyc7002/Documentation
Michal Hocko c9bff3eebc mm, page_alloc: rip out ZONELIST_ORDER_ZONE
Patch series "cleanup zonelists initialization", v1.

This is aimed at cleaning up the zonelists initialization code we have
but the primary motivation was bug report [2] which got resolved but the
usage of stop_machine is just too ugly to live.  Most patches are
straightforward but 3 of them need a special consideration.

Patch 1 removes zone ordered zonelists completely.  I am CCing linux-api
because this is a user visible change.  As I argue in the patch
description I do not think we have a strong usecase for it these days.
I have kept sysctl in place and warn into the log if somebody tries to
configure zone lists ordering.  If somebody has a real usecase for it we
can revert this patch but I do not expect anybody will actually notice
runtime differences.  This patch is not strictly needed for the rest but
it made patch 6 easier to implement.

Patch 7 removes stop_machine from build_all_zonelists without adding any
special synchronization between iterators and updater which I _believe_
is acceptable as explained in the changelog.  I hope I am not missing
anything.

Patch 8 then removes zonelists_mutex which is kind of ugly as well and
not really needed AFAICS but a care should be taken when double checking
my thinking.

This patch (of 9):

Supporting zone ordered zonelists costs us just a lot of code while the
usefulness is arguable if existent at all.  Mel has already made node
ordering default on 64b systems.  32b systems are still using
ZONELIST_ORDER_ZONE because it is considered better to fallback to a
different NUMA node rather than consume precious lowmem zones.

This argument is, however, weaken by the fact that the memory reclaim
has been reworked to be node rather than zone oriented.  This means that
lowmem requests have to skip over all highmem pages on LRUs already and
so zone ordering doesn't save the reclaim time much.  So the only
advantage of the zone ordering is under a light memory pressure when
highmem requests do not ever hit into lowmem zones and the lowmem
pressure doesn't need to reclaim.

Considering that 32b NUMA systems are rather suboptimal already and it
is generally advisable to use 64b kernel on such a HW I believe we
should rather care about the code maintainability and just get rid of
ZONELIST_ORDER_ZONE altogether.  Keep systcl in place and warn if
somebody tries to set zone ordering either from kernel command line or
the sysctl.

[mhocko@suse.com: reading vm.numa_zonelist_order will never terminate]
Link: http://lkml.kernel.org/r/20170721143915.14161-2-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06 17:27:25 -07:00
..
ABI zram: add config and doc file for writeback feature 2017-09-06 17:27:25 -07:00
accounting
acpi
admin-guide mm, page_alloc: rip out ZONELIST_ORDER_ZONE 2017-09-06 17:27:25 -07:00
aoe
arm
arm64
auxdisplay
backlight
blackfin
block
blockdev zram: add config and doc file for writeback feature 2017-09-06 17:27:25 -07:00
bus-devices
cdrom
cgroup-v1
cma
connector
console
core-api
cpu-freq
cpuidle
cris
crypto
dev-tools
device-mapper
devicetree Power management updates for v4.14-rc1 2017-09-05 12:19:08 -07:00
dmaengine
doc-guide
driver-api This is the bulk of the GPIO changes for the v4.14 cycle: 2017-09-05 11:49:48 -07:00
driver-model
early-userspace
EDID
extcon
fault-injection
fb
features
filesystems dax: use common 4k zero page for dax mmap reads 2017-09-06 17:27:24 -07:00
firmware_class
fmc
fpga
frv
gpio
gpu
hid
hwmon
i2c
ia64
ide
iio
infiniband
input
ioctl
isdn
kbuild
kdump
kernel-hacking
laptops
leds
lightnvm
livepatch
locking
m68k
md
media
memory-devices
metag
mic
mips
misc-devices
mmc
mn10300
mtd
namespaces
netlabel
networking
nfc
nios2
nvdimm
nvmem
parisc
PCI
pcmcia
perf
phy
platform
power
powerpc
pps
process
pti
ptp
rapidio
RCU
s390
scheduler
scsi
security
serial
sh
sound
sparc
sphinx
sphinx-static
spi
sysctl mm, page_alloc: rip out ZONELIST_ORDER_ZONE 2017-09-06 17:27:25 -07:00
target
thermal
timers
trace
translations
usb
userspace-api
virtual
vm mm, page_alloc: rip out ZONELIST_ORDER_ZONE 2017-09-06 17:27:25 -07:00
w1
watchdog
wimax
x86
xtensa
.gitignore
00-INDEX
atomic_bitops.txt
atomic_t.txt
bcache.txt
bt8xxgpio.txt
btmrvl.txt
bus-virt-phys-mapping.txt
cachetlb.txt
cgroup-v2.txt
Changes
circular-buffers.txt
clk.txt
CodingStyle
conf.py
cpu-load.txt
cputopology.txt
crc32.txt
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt
dell_rbu.txt
digsig.txt
DMA-API-HOWTO.txt
DMA-API.txt
DMA-attributes.txt
DMA-ISA-LPC.txt
docutils.conf
dontdiff
efi-stub.txt
eisa.txt
flexible-arrays.txt
futex-requeue-pi.txt
gcc-plugins.txt
highuid.txt
hw_random.txt
hwspinlock.txt
index.rst
intel_txt.txt
Intel-IOMMU.txt
io_ordering.txt
io-mapping.txt
iostats.txt
IPMI.txt
IRQ-affinity.txt
IRQ-domain.txt
IRQ.txt
irqflags-tracing.txt
isa.txt
isapnp.txt
kernel-doc-nano-HOWTO.txt
kernel-per-CPU-kthreads.txt
kobject.txt
kprobes.txt
kref.txt
ldm.txt
lockup-watchdogs.txt
logo.gif
logo.txt
lsm.txt
lzo.txt
mailbox.txt
Makefile
memory-barriers.txt
memory-hotplug.txt
men-chameleon-bus.txt
nommu-mmap.txt
ntb.txt
numastat.txt
padata.txt
parport-lowlevel.txt
percpu-rw-semaphore.txt
phy.txt
pi-futex.txt
pnp.txt
preempt-locking.txt
printk-formats.txt
pwm.txt
rbtree.txt
remoteproc.txt
rfkill.txt
robust-futex-ABI.txt
robust-futexes.txt
rpmsg.txt
rtc.txt
SAK.txt
sgi-ioc4.txt
siphash.txt
SM501.txt
smsc_ece1099.txt
static-keys.txt
SubmittingPatches
svga.txt
switchtec.txt
sync_file.txt
tee.txt
this_cpu_ops.txt
unaligned-memory-access.txt
vfio-mediated-device.txt
vfio.txt
video-output.txt
xillybus.txt
xz.txt
zorro.txt