kernel_optimize_test/Documentation
Mel Gorman 24512228b7 mm: do not boost watermarks to avoid fragmentation for the DISCONTIG memory model
Mikulas Patocka reported that commit 1c30844d2d ("mm: reclaim small
amounts of memory when an external fragmentation event occurs") "broke"
memory management on parisc.

The machine is not NUMA but the DISCONTIG model creates three pgdats
even though it's a UMA machine for the following ranges

        0) Start 0x0000000000000000 End 0x000000003fffffff Size   1024 MB
        1) Start 0x0000000100000000 End 0x00000001bfdfffff Size   3070 MB
        2) Start 0x0000004040000000 End 0x00000040ffffffff Size   3072 MB

Mikulas reported:

	With the patch 1c30844d2, the kernel will incorrectly reclaim the
	first zone when it fills up, ignoring the fact that there are two
	completely free zones. Basiscally, it limits cache size to 1GiB.

	For example, if I run:
	# dd if=/dev/sda of=/dev/null bs=1M count=2048

	- with the proper kernel, there should be "Buffers - 2GiB"
	when this command finishes. With the patch 1c30844d2, buffers
	will consume just 1GiB or slightly more, because the kernel was
	incorrectly reclaiming them.

The page allocator and reclaim makes assumptions that pgdats really
represent NUMA nodes and zones represent ranges and makes decisions on
that basis.  Watermark boosting for small pgdats leads to unexpected
results even though this would have behaved reasonably on SPARSEMEM.

DISCONTIG is essentially deprecated and even parisc plans to move to
SPARSEMEM so there is no need to be fancy, this patch simply disables
watermark boosting by default on DISCONTIGMEM.

Link: http://lkml.kernel.org/r/20190419094335.GJ18914@techsingularity.net
Fixes: 1c30844d2d ("mm: reclaim small amounts of memory when an external fragmentation event occurs")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-04-26 09:18:05 -07:00
..
ABI device-dax for 5.1 2019-03-16 13:05:32 -07:00
accelerators
accounting psi: clarify the units used in pressure files 2019-04-05 16:02:31 -10:00
acpi ACPI: Documentation: Fix path for acpidbg tool 2019-03-07 11:28:33 +01:00
admin-guide for-5.1/block-post-20190315 2019-03-16 12:36:39 -07:00
aoe
arm
arm64 arm64 updates for 5.1: 2019-03-10 10:17:23 -07:00
auxdisplay
backlight
block
blockdev
bpf bpf, doc: fix BTF docs reflow of bullet list 2019-03-26 13:13:42 -07:00
bus-devices
cdrom
cgroup-v1 A fairly routine cycle for docs - lots of typo fixes, some new documents, 2019-03-09 09:56:17 -08:00
cma
connector
console
core-api Merge branch 'akpm' (patches from Andrew) 2019-03-12 10:39:53 -07:00
cpu-freq
crypto
dev-tools
device-mapper
devicetree dt-bindings: add an explanation for internal phy-mode 2019-04-21 11:24:08 -07:00
doc-guide
driver-api dmaengine updates for v5.1-rc1 2019-03-14 09:11:54 -07:00
driver-model Merge branches 'clk-optional', 'clk-devm-clkdev-register', 'clk-allwinner', 'clk-meson' and 'clk-renesas' into clk-next 2019-03-08 10:27:21 -08:00
early-userspace
EDID
extcon
fault-injection
fb
features
filesystems vfs: Update mount API docs 2019-03-28 08:54:20 -07:00
firmware_class
fmc
fpga
gpio
gpu
hid
hwmon A fairly routine cycle for docs - lots of typo fixes, some new documents, 2019-03-09 09:56:17 -08:00
i2c i2c: i801: Add support for Intel Comet Lake 2019-03-20 17:42:23 +01:00
ia64
ide
iio
infiniband
input
interconnect
ioctl
isdn
kbuild kbuild: force all architectures except um to include mandatory-y 2019-03-17 12:56:32 +09:00
kdump
kernel-hacking
laptops
leds
lightnvm
livepatch
locking
m68k
maintainer
md
media Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2019-04-19 10:28:27 -07:00
memory-devices
mic
mips
misc-devices
mmc
mtd
namespaces
netlabel
networking Documentation: decnet: remove reference to CONFIG_DECNET_ROUTE_FWMARK 2019-04-21 11:25:11 -07:00
nfc
nios2
nvdimm
nvmem
openrisc
parisc
PCI
pcmcia
perf
phy
platform
power
powerpc
pps
process A fairly routine cycle for docs - lots of typo fixes, some new documents, 2019-03-09 09:56:17 -08:00
pti
ptp
rapidio
RCU A fairly routine cycle for docs - lots of typo fixes, some new documents, 2019-03-09 09:56:17 -08:00
riscv
s390
scheduler
scsi
security
serial
sh
sound
sparc
sphinx
sphinx-static
spi
sysctl mm: do not boost watermarks to avoid fragmentation for the DISCONTIG memory model 2019-04-26 09:18:05 -07:00
target
thermal
timers
trace
translations A fairly routine cycle for docs - lots of typo fixes, some new documents, 2019-03-09 09:56:17 -08:00
usb
userspace-api
virtual Documentation: kvm: clarify KVM_SET_USER_MEMORY_REGION 2019-03-28 17:30:11 +01:00
vm
w1
watchdog
wimax
x86
xilinx
xtensa
.gitignore
atomic_bitops.txt
atomic_t.txt
bt8xxgpio.txt
btmrvl.txt
bus-virt-phys-mapping.txt
Changes
clearing-warn-once.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 virtio: fixes, cleanups 2019-03-10 12:47:57 -07:00
DMA-attributes.txt
DMA-ISA-LPC.txt
docutils.conf
dontdiff kernel/configs: use .incbin directive to embed config_data.gz 2019-03-07 18:32:02 -08:00
efi-stub.txt
eisa.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-per-CPU-kthreads.txt
kobject.txt
kprobes.txt
kref.txt
ldm.txt
lockup-watchdogs.txt
logo.gif
logo.txt
lsm.txt
lzo.txt lib/lzo: fix bugs for very short or empty input 2019-04-05 16:02:30 -10:00
mailbox.txt
Makefile
memory-barriers.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
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
speculation.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