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Dave Hansen c4e1be9ec1 mm, sparsemem: break out of loops early 
There are a number of times that we loop over NR_MEM_SECTIONS, looking
for section_present() on each section.  But, when we have very large
physical address spaces (large MAX_PHYSMEM_BITS), NR_MEM_SECTIONS
becomes very large, making the loops quite long.

With MAX_PHYSMEM_BITS=46 and a section size of 128MB, the current loops
are 512k iterations, which we barely notice on modern hardware.  But,
raising MAX_PHYSMEM_BITS higher (like we will see on systems that
support 5-level paging) makes this 64x longer and we start to notice,
especially on slower systems like simulators.  A 10-second delay for
512k iterations is annoying.  But, a 640- second delay is crippling.

This does not help if we have extremely sparse physical address spaces,
but those are quite rare.  We expect that most of the "slow" systems
where this matters will also be quite small and non-sparse.

To fix this, we track the highest section we've ever encountered.  This
lets us know when we will *never* see another section_present(), and
lets us break out of the loops earlier.

Doing the whole for_each_present_section_nr() macro is probably
overkill, but it will ensure that any future loop iterations that we
grow are more likely to be correct.

Kirrill said "It shaved almost 40 seconds from boot time in qemu with
5-level paging enabled for me".

Link: http://lkml.kernel.org/r/20170504174434.C45A4735@viggo.jf.intel.com
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2017-07-06 16:24:31 -07:00
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accessibility
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acpi arm64 updates for 4.13: 2017-07-05 17:09:27 -07:00
amba
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android
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ata Merge branch 'for-4.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata 2017-07-06 09:41:58 -07:00
atm net: convert sock.sk_wmem_alloc from atomic_t to refcount_t 2017-07-01 07:39:08 -07:00
auxdisplay
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base mm, sparsemem: break out of loops early 2017-07-06 16:24:31 -07:00
bcma
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block Merge branch 'work.read_write' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-05 14:35:57 -07:00
bluetooth Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
bus ARM: SoC driver updates 2017-07-04 14:47:47 -07:00
cdrom block: don't set bounce limit in blk_init_queue 2017-06-27 12:13:45 -06:00
char arm64 updates for 4.13: 2017-07-05 17:09:27 -07:00
clk ARM: Device-tree updates 2017-07-04 14:37:25 -07:00
clocksource ARM: SoC driver updates 2017-07-04 14:47:47 -07:00
connector
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cpufreq ARM: SoC driver updates 2017-07-04 14:47:47 -07:00
cpuidle Power management updates for v4.13-rc1 2017-07-04 13:39:41 -07:00
crypto Cavium CNN55XX: fix broken default Kconfig entry 2017-07-05 13:03:05 -07:00
dax
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dca
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devfreq
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dio
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dma dmaengine: omap-dma: port_window support correction for both direction 2017-06-20 11:45:01 +08:00
dma-buf
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edac EDAC, pnd2: Fix Apollo Lake DIMM detection 2017-06-29 10:37:50 +02:00
eisa
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extcon
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firewire networking: make skb_push & __skb_push return void pointers 2017-06-16 11:48:40 -04:00
firmware arm64 updates for 4.13: 2017-07-05 17:09:27 -07:00
fmc
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fpga
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fsi
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gpio driver core patches for 4.13-rc1 2017-07-03 20:27:48 -07:00
gpu Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-03 13:08:04 -07:00
hid driver core patches for 4.13-rc1 2017-07-03 20:27:48 -07:00
hsi HSI changes for the v4.13 series 2017-07-04 14:28:22 -07:00
hv
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hwmon hwmon: (aspeed-pwm-tacho) Poll with short sleeps. 2017-06-24 08:58:06 -07:00
hwspinlock
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hwtracing Char/Misc patches for 4.13-rc1 2017-07-03 20:55:59 -07:00
i2c Char/Misc patches for 4.13-rc1 2017-07-03 20:55:59 -07:00
ide block: Change argument type of scsi_req_init() 2017-06-20 19:27:14 -06:00
idle intel_idle: Use more common logging style 2017-06-29 22:58:35 +02:00
iio hwmon updates for v4.13: 2017-07-04 11:48:27 -07:00
infiniband Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
input Input: synaptics-rmi4 - only read the F54 query registers which are used 2017-06-23 00:08:48 -07:00
iommu Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-03 16:50:31 -07:00
ipack
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irqchip arm64 updates for 4.13: 2017-07-05 17:09:27 -07:00
isdn Merge branch 'work.misc-set_fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-05 13:13:32 -07:00
leds LED fixes for 4.12-rc6 2017-06-18 08:51:35 +09:00
lguest
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lightnvm lightnvm: pblk: set line bitmap check under debug 2017-06-30 11:08:18 -06:00
macintosh Merge branch 'work.misc-set_fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-05 13:13:32 -07:00
mailbox
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mcb
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md Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-03 13:08:04 -07:00
media networking: make skb_put & friends return void pointers 2017-06-16 11:48:39 -04:00
memory ARM: SoC driver updates 2017-07-04 14:47:47 -07:00
memstick
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message
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mfd Merge remote-tracking branches 'regulator/topic/settle', 'regulator/topic/tps65910' and 'regulator/topic/tps65917' into regulator-next 2017-07-03 16:52:21 +01:00
misc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
mmc MMC core: 2017-07-04 11:11:56 -07:00
mtd There has been a fair amount of activity in the docs tree this time 2017-07-03 21:13:25 -07:00
mux
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net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
nfc NFC 4.13 pull request 2017-07-01 14:30:39 -07:00
ntb ntb: no sleep in ntb_async_tx_submit 2017-06-19 14:24:41 -04:00
nubus
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nvdimm block: don't bother with bounce limits for make_request drivers 2017-06-27 12:13:45 -06:00
nvme Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-03 16:50:31 -07:00
nvmem
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of Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-06-15 11:59:32 -04:00
oprofile
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parisc parisc: ->mapping_error 2017-07-05 21:46:42 +02:00
parport
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pci Power management updates for v4.13-rc1 2017-07-04 13:39:41 -07:00
pcmcia
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perf Merge branch 'aarch64/for-next/ras-apei' into aarch64/for-next/core 2017-06-26 10:54:27 +01:00
phy phy: bcm-ns-usb3: add MDIO driver using proper bus layer 2017-06-16 13:22:26 +05:30
pinctrl Revert "pinctrl: rockchip: avoid hardirq-unsafe functions in irq_chip" 2017-06-29 15:03:24 +02:00
platform Power management updates for v4.13-rc1 2017-07-04 13:39:41 -07:00
pnp ACPI / PM: Consolidate device wakeup settings code 2017-06-28 01:52:32 +02:00
power power supply and reset changes for the v4.13 series 2017-07-04 14:25:14 -07:00
powercap powercap/RAPL: prevent overridding bits outside of the mask 2017-06-28 00:38:34 +02:00
pps
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ps3
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ptp ptp: Add a ptp clock driver for Broadcom DTE 2017-06-15 12:07:15 -04:00
pwm
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rapidio
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ras arm64 updates for 4.13: 2017-07-05 17:09:27 -07:00
regulator Merge remote-tracking branches 'regulator/topic/settle', 'regulator/topic/tps65910' and 'regulator/topic/tps65917' into regulator-next 2017-07-03 16:52:21 +01:00
remoteproc
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reset ARM: SoC driver updates 2017-07-04 14:47:47 -07:00
rpmsg Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
rtc sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming 2017-06-20 12:19:14 +02:00
s390 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
sbus block: don't set bounce limit in blk_init_queue 2017-06-27 12:13:45 -06:00
scsi Merge branch 'for-4.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata 2017-07-06 09:41:58 -07:00
sfi
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sh drivers/sh/intc/virq.c: delete an error message for a failed memory allocation in add_virq_to_pirq() 2017-07-06 16:24:30 -07:00
sn
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soc ARM: SoC driver updates 2017-07-04 14:47:47 -07:00
spi Merge remote-tracking branches 'spi/topic/spidev', 'spi/topic/st-ssc4' and 'spi/topic/stm32' into spi-next 2017-07-03 16:21:12 +01:00
spmi
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ssb
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staging Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
target Merge branch 'work.read_write' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-05 14:35:57 -07:00
tc
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tee
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thermal USB/PHY patches for 4.13-rc1 2017-07-03 19:30:55 -07:00
thunderbolt
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tty Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
uio
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usb Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
uwb driver core patches for 4.13-rc1 2017-07-03 20:27:48 -07:00
vfio sched/wait: Rename wait_queue_t => wait_queue_entry_t 2017-06-20 12:18:27 +02:00
vhost Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-07-05 12:31:59 -07:00
video video: fbdev: udlfb: drop log level for blanking 2017-06-14 12:40:36 +02:00
virt
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virtio virtio_balloon: disable VIOMMU support 2017-06-18 23:13:35 +03:00
vlynq
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vme
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w1
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watchdog
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xen Merge branch 'ras-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-03 18:33:03 -07:00
zorro
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Kconfig
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Makefile
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