mirror of
https://github.com/armbian/linux-cix.git
synced 2026-01-06 12:30:45 -08:00
Merge tag 'docs-4.20' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet: "This is a fairly typical cycle for documentation. There's some welcome readability improvements for the formatted output, some LICENSES updates including the addition of the ISC license, the removal of the unloved and unmaintained 00-INDEX files, the deprecated APIs document from Kees, more MM docs from Mike Rapoport, and the usual pile of typo fixes and corrections" * tag 'docs-4.20' of git://git.lwn.net/linux: (41 commits) docs: Fix typos in histogram.rst docs: Introduce deprecated APIs list kernel-doc: fix declaration type determination doc: fix a typo in adding-syscalls.rst docs/admin-guide: memory-hotplug: remove table of contents doc: printk-formats: Remove bogus kobject references for device nodes Documentation: preempt-locking: Use better example dm flakey: Document "error_writes" feature docs/completion.txt: Fix a couple of punctuation nits LICENSES: Add ISC license text LICENSES: Add note to CDDL-1.0 license that it should not be used docs/core-api: memory-hotplug: add some details about locking internals docs/core-api: rename memory-hotplug-notifier to memory-hotplug docs: improve readability for people with poorer eyesight yama: clarify ptrace_scope=2 in Yama documentation docs/vm: split memory hotplug notifier description to Documentation/core-api docs: move memory hotplug description into admin-guide/mm doc: Fix acronym "FEKEK" in ecryptfs docs: fix some broken documentation references iommu: Fix passthrough option documentation ...
This commit is contained in:
Linus Torvalds
@@ -1,428 +0,0 @@
|
||||
|
||||
This is a brief list of all the files in ./linux/Documentation and what
|
||||
they contain. If you add a documentation file, please list it here in
|
||||
alphabetical order as well, or risk being hunted down like a rabid dog.
|
||||
Please keep the descriptions small enough to fit on one line.
|
||||
Thanks -- Paul G.
|
||||
|
||||
Following translations are available on the WWW:
|
||||
|
||||
- Japanese, maintained by the JF Project (jf@listserv.linux.or.jp), at
|
||||
http://linuxjf.sourceforge.jp/
|
||||
|
||||
00-INDEX
|
||||
- this file.
|
||||
ABI/
|
||||
- info on kernel <-> userspace ABI and relative interface stability.
|
||||
CodingStyle
|
||||
- nothing here, just a pointer to process/coding-style.rst.
|
||||
DMA-API.txt
|
||||
- DMA API, pci_ API & extensions for non-consistent memory machines.
|
||||
DMA-API-HOWTO.txt
|
||||
- Dynamic DMA mapping Guide
|
||||
DMA-ISA-LPC.txt
|
||||
- How to do DMA with ISA (and LPC) devices.
|
||||
DMA-attributes.txt
|
||||
- listing of the various possible attributes a DMA region can have
|
||||
EDID/
|
||||
- directory with info on customizing EDID for broken gfx/displays.
|
||||
IPMI.txt
|
||||
- info on Linux Intelligent Platform Management Interface (IPMI) Driver.
|
||||
IRQ-affinity.txt
|
||||
- how to select which CPU(s) handle which interrupt events on SMP.
|
||||
IRQ-domain.txt
|
||||
- info on interrupt numbering and setting up IRQ domains.
|
||||
IRQ.txt
|
||||
- description of what an IRQ is.
|
||||
Intel-IOMMU.txt
|
||||
- basic info on the Intel IOMMU virtualization support.
|
||||
Makefile
|
||||
- It's not of interest for those who aren't touching the build system.
|
||||
PCI/
|
||||
- info related to PCI drivers.
|
||||
RCU/
|
||||
- directory with info on RCU (read-copy update).
|
||||
SAK.txt
|
||||
- info on Secure Attention Keys.
|
||||
SM501.txt
|
||||
- Silicon Motion SM501 multimedia companion chip
|
||||
SubmittingPatches
|
||||
- nothing here, just a pointer to process/coding-style.rst.
|
||||
accounting/
|
||||
- documentation on accounting and taskstats.
|
||||
acpi/
|
||||
- info on ACPI-specific hooks in the kernel.
|
||||
admin-guide/
|
||||
- info related to Linux users and system admins.
|
||||
aoe/
|
||||
- description of AoE (ATA over Ethernet) along with config examples.
|
||||
arm/
|
||||
- directory with info about Linux on the ARM architecture.
|
||||
arm64/
|
||||
- directory with info about Linux on the 64 bit ARM architecture.
|
||||
auxdisplay/
|
||||
- misc. LCD driver documentation (cfag12864b, ks0108).
|
||||
backlight/
|
||||
- directory with info on controlling backlights in flat panel displays
|
||||
block/
|
||||
- info on the Block I/O (BIO) layer.
|
||||
blockdev/
|
||||
- info on block devices & drivers
|
||||
bt8xxgpio.txt
|
||||
- info on how to modify a bt8xx video card for GPIO usage.
|
||||
btmrvl.txt
|
||||
- info on Marvell Bluetooth driver usage.
|
||||
bus-devices/
|
||||
- directory with info on TI GPMC (General Purpose Memory Controller)
|
||||
bus-virt-phys-mapping.txt
|
||||
- how to access I/O mapped memory from within device drivers.
|
||||
cdrom/
|
||||
- directory with information on the CD-ROM drivers that Linux has.
|
||||
cgroup-v1/
|
||||
- cgroups v1 features, including cpusets and memory controller.
|
||||
cma/
|
||||
- Continuous Memory Area (CMA) debugfs interface.
|
||||
conf.py
|
||||
- It's not of interest for those who aren't touching the build system.
|
||||
connector/
|
||||
- docs on the netlink based userspace<->kernel space communication mod.
|
||||
console/
|
||||
- documentation on Linux console drivers.
|
||||
core-api/
|
||||
- documentation on kernel core components.
|
||||
cpu-freq/
|
||||
- info on CPU frequency and voltage scaling.
|
||||
cpu-hotplug.txt
|
||||
- document describing CPU hotplug support in the Linux kernel.
|
||||
cpu-load.txt
|
||||
- document describing how CPU load statistics are collected.
|
||||
cpuidle/
|
||||
- info on CPU_IDLE, CPU idle state management subsystem.
|
||||
cputopology.txt
|
||||
- documentation on how CPU topology info is exported via sysfs.
|
||||
crc32.txt
|
||||
- brief tutorial on CRC computation
|
||||
crypto/
|
||||
- directory with info on the Crypto API.
|
||||
dcdbas.txt
|
||||
- information on the Dell Systems Management Base Driver.
|
||||
debugging-modules.txt
|
||||
- some notes on debugging modules after Linux 2.6.3.
|
||||
debugging-via-ohci1394.txt
|
||||
- how to use firewire like a hardware debugger memory reader.
|
||||
dell_rbu.txt
|
||||
- document demonstrating the use of the Dell Remote BIOS Update driver.
|
||||
dev-tools/
|
||||
- directory with info on development tools for the kernel.
|
||||
device-mapper/
|
||||
- directory with info on Device Mapper.
|
||||
dmaengine/
|
||||
- the DMA engine and controller API guides.
|
||||
devicetree/
|
||||
- directory with info on device tree files used by OF/PowerPC/ARM
|
||||
digsig.txt
|
||||
-info on the Digital Signature Verification API
|
||||
dma-buf-sharing.txt
|
||||
- the DMA Buffer Sharing API Guide
|
||||
docutils.conf
|
||||
- nothing here. Just a configuration file for docutils.
|
||||
dontdiff
|
||||
- file containing a list of files that should never be diff'ed.
|
||||
driver-api/
|
||||
- the Linux driver implementer's API guide.
|
||||
driver-model/
|
||||
- directory with info about Linux driver model.
|
||||
early-userspace/
|
||||
- info about initramfs, klibc, and userspace early during boot.
|
||||
efi-stub.txt
|
||||
- How to use the EFI boot stub to bypass GRUB or elilo on EFI systems.
|
||||
eisa.txt
|
||||
- info on EISA bus support.
|
||||
extcon/
|
||||
- directory with porting guide for Android kernel switch driver.
|
||||
isa.txt
|
||||
- info on EISA bus support.
|
||||
fault-injection/
|
||||
- dir with docs about the fault injection capabilities infrastructure.
|
||||
fb/
|
||||
- directory with info on the frame buffer graphics abstraction layer.
|
||||
features/
|
||||
- status of feature implementation on different architectures.
|
||||
filesystems/
|
||||
- info on the vfs and the various filesystems that Linux supports.
|
||||
firmware_class/
|
||||
- request_firmware() hotplug interface info.
|
||||
flexible-arrays.txt
|
||||
- how to make use of flexible sized arrays in linux
|
||||
fmc/
|
||||
- information about the FMC bus abstraction
|
||||
fpga/
|
||||
- FPGA Manager Core.
|
||||
futex-requeue-pi.txt
|
||||
- info on requeueing of tasks from a non-PI futex to a PI futex
|
||||
gcc-plugins.txt
|
||||
- GCC plugin infrastructure.
|
||||
gpio/
|
||||
- gpio related documentation
|
||||
gpu/
|
||||
- directory with information on GPU driver developer's guide.
|
||||
hid/
|
||||
- directory with information on human interface devices
|
||||
highuid.txt
|
||||
- notes on the change from 16 bit to 32 bit user/group IDs.
|
||||
hwspinlock.txt
|
||||
- hardware spinlock provides hardware assistance for synchronization
|
||||
timers/
|
||||
- info on the timer related topics
|
||||
hw_random.txt
|
||||
- info on Linux support for random number generator in i8xx chipsets.
|
||||
hwmon/
|
||||
- directory with docs on various hardware monitoring drivers.
|
||||
i2c/
|
||||
- directory with info about the I2C bus/protocol (2 wire, kHz speed).
|
||||
x86/i386/
|
||||
- directory with info about Linux on Intel 32 bit architecture.
|
||||
ia64/
|
||||
- directory with info about Linux on Intel 64 bit architecture.
|
||||
ide/
|
||||
- Information regarding the Enhanced IDE drive.
|
||||
iio/
|
||||
- info on industrial IIO configfs support.
|
||||
index.rst
|
||||
- main index for the documentation at ReST format.
|
||||
infiniband/
|
||||
- directory with documents concerning Linux InfiniBand support.
|
||||
input/
|
||||
- info on Linux input device support.
|
||||
intel_txt.txt
|
||||
- info on intel Trusted Execution Technology (intel TXT).
|
||||
io-mapping.txt
|
||||
- description of io_mapping functions in linux/io-mapping.h
|
||||
io_ordering.txt
|
||||
- info on ordering I/O writes to memory-mapped addresses.
|
||||
ioctl/
|
||||
- directory with documents describing various IOCTL calls.
|
||||
iostats.txt
|
||||
- info on I/O statistics Linux kernel provides.
|
||||
irqflags-tracing.txt
|
||||
- how to use the irq-flags tracing feature.
|
||||
isapnp.txt
|
||||
- info on Linux ISA Plug & Play support.
|
||||
isdn/
|
||||
- directory with info on the Linux ISDN support, and supported cards.
|
||||
kbuild/
|
||||
- directory with info about the kernel build process.
|
||||
kdump/
|
||||
- directory with mini HowTo on getting the crash dump code to work.
|
||||
doc-guide/
|
||||
- how to write and format reStructuredText kernel documentation
|
||||
kernel-per-CPU-kthreads.txt
|
||||
- List of all per-CPU kthreads and how they introduce jitter.
|
||||
kobject.txt
|
||||
- info of the kobject infrastructure of the Linux kernel.
|
||||
kprobes.txt
|
||||
- documents the kernel probes debugging feature.
|
||||
kref.txt
|
||||
- docs on adding reference counters (krefs) to kernel objects.
|
||||
laptops/
|
||||
- directory with laptop related info and laptop driver documentation.
|
||||
ldm.txt
|
||||
- a brief description of LDM (Windows Dynamic Disks).
|
||||
leds/
|
||||
- directory with info about LED handling under Linux.
|
||||
livepatch/
|
||||
- info on kernel live patching.
|
||||
locking/
|
||||
- directory with info about kernel locking primitives
|
||||
lockup-watchdogs.txt
|
||||
- info on soft and hard lockup detectors (aka nmi_watchdog).
|
||||
logo.gif
|
||||
- full colour GIF image of Linux logo (penguin - Tux).
|
||||
logo.txt
|
||||
- info on creator of above logo & site to get additional images from.
|
||||
lsm.txt
|
||||
- Linux Security Modules: General Security Hooks for Linux
|
||||
lzo.txt
|
||||
- kernel LZO decompressor input formats
|
||||
m68k/
|
||||
- directory with info about Linux on Motorola 68k architecture.
|
||||
mailbox.txt
|
||||
- How to write drivers for the common mailbox framework (IPC).
|
||||
md/
|
||||
- directory with info about Linux Software RAID
|
||||
media/
|
||||
- info on media drivers: uAPI, kAPI and driver documentation.
|
||||
memory-barriers.txt
|
||||
- info on Linux kernel memory barriers.
|
||||
memory-devices/
|
||||
- directory with info on parts like the Texas Instruments EMIF driver
|
||||
memory-hotplug.txt
|
||||
- Hotpluggable memory support, how to use and current status.
|
||||
men-chameleon-bus.txt
|
||||
- info on MEN chameleon bus.
|
||||
mic/
|
||||
- Intel Many Integrated Core (MIC) architecture device driver.
|
||||
mips/
|
||||
- directory with info about Linux on MIPS architecture.
|
||||
misc-devices/
|
||||
- directory with info about devices using the misc dev subsystem
|
||||
mmc/
|
||||
- directory with info about the MMC subsystem
|
||||
mtd/
|
||||
- directory with info about memory technology devices (flash)
|
||||
namespaces/
|
||||
- directory with various information about namespaces
|
||||
netlabel/
|
||||
- directory with information on the NetLabel subsystem.
|
||||
networking/
|
||||
- directory with info on various aspects of networking with Linux.
|
||||
nfc/
|
||||
- directory relating info about Near Field Communications support.
|
||||
nios2/
|
||||
- Linux on the Nios II architecture.
|
||||
nommu-mmap.txt
|
||||
- documentation about no-mmu memory mapping support.
|
||||
numastat.txt
|
||||
- info on how to read Numa policy hit/miss statistics in sysfs.
|
||||
ntb.txt
|
||||
- info on Non-Transparent Bridge (NTB) drivers.
|
||||
nvdimm/
|
||||
- info on non-volatile devices.
|
||||
nvmem/
|
||||
- info on non volatile memory framework.
|
||||
output/
|
||||
- default directory where html/LaTeX/pdf files will be written.
|
||||
padata.txt
|
||||
- An introduction to the "padata" parallel execution API
|
||||
parisc/
|
||||
- directory with info on using Linux on PA-RISC architecture.
|
||||
parport-lowlevel.txt
|
||||
- description and usage of the low level parallel port functions.
|
||||
pcmcia/
|
||||
- info on the Linux PCMCIA driver.
|
||||
percpu-rw-semaphore.txt
|
||||
- RCU based read-write semaphore optimized for locking for reading
|
||||
perf/
|
||||
- info about the APM X-Gene SoC Performance Monitoring Unit (PMU).
|
||||
phy/
|
||||
- ino on Samsung USB 2.0 PHY adaptation layer.
|
||||
phy.txt
|
||||
- Description of the generic PHY framework.
|
||||
pi-futex.txt
|
||||
- documentation on lightweight priority inheritance futexes.
|
||||
pinctrl.txt
|
||||
- info on pinctrl subsystem and the PINMUX/PINCONF and drivers
|
||||
platform/
|
||||
- List of supported hardware by compal and Dell laptop.
|
||||
pnp.txt
|
||||
- Linux Plug and Play documentation.
|
||||
power/
|
||||
- directory with info on Linux PCI power management.
|
||||
powerpc/
|
||||
- directory with info on using Linux with the PowerPC.
|
||||
prctl/
|
||||
- directory with info on the priveledge control subsystem
|
||||
preempt-locking.txt
|
||||
- info on locking under a preemptive kernel.
|
||||
process/
|
||||
- how to work with the mainline kernel development process.
|
||||
pps/
|
||||
- directory with information on the pulse-per-second support
|
||||
pti/
|
||||
- directory with info on Intel MID PTI.
|
||||
ptp/
|
||||
- directory with info on support for IEEE 1588 PTP clocks in Linux.
|
||||
pwm.txt
|
||||
- info on the pulse width modulation driver subsystem
|
||||
rapidio/
|
||||
- directory with info on RapidIO packet-based fabric interconnect
|
||||
rbtree.txt
|
||||
- info on what red-black trees are and what they are for.
|
||||
remoteproc.txt
|
||||
- info on how to handle remote processor (e.g. AMP) offloads/usage.
|
||||
rfkill.txt
|
||||
- info on the radio frequency kill switch subsystem/support.
|
||||
robust-futex-ABI.txt
|
||||
- documentation of the robust futex ABI.
|
||||
robust-futexes.txt
|
||||
- a description of what robust futexes are.
|
||||
rpmsg.txt
|
||||
- info on the Remote Processor Messaging (rpmsg) Framework
|
||||
rtc.txt
|
||||
- notes on how to use the Real Time Clock (aka CMOS clock) driver.
|
||||
s390/
|
||||
- directory with info on using Linux on the IBM S390.
|
||||
scheduler/
|
||||
- directory with info on the scheduler.
|
||||
scsi/
|
||||
- directory with info on Linux scsi support.
|
||||
security/
|
||||
- directory that contains security-related info
|
||||
serial/
|
||||
- directory with info on the low level serial API.
|
||||
sgi-ioc4.txt
|
||||
- description of the SGI IOC4 PCI (multi function) device.
|
||||
sh/
|
||||
- directory with info on porting Linux to a new architecture.
|
||||
smsc_ece1099.txt
|
||||
-info on the smsc Keyboard Scan Expansion/GPIO Expansion device.
|
||||
sound/
|
||||
- directory with info on sound card support.
|
||||
spi/
|
||||
- overview of Linux kernel Serial Peripheral Interface (SPI) support.
|
||||
sphinx/
|
||||
- no documentation here, just files required by Sphinx toolchain.
|
||||
sphinx-static/
|
||||
- no documentation here, just files required by Sphinx toolchain.
|
||||
static-keys.txt
|
||||
- info on how static keys allow debug code in hotpaths via patching
|
||||
svga.txt
|
||||
- short guide on selecting video modes at boot via VGA BIOS.
|
||||
sync_file.txt
|
||||
- Sync file API guide.
|
||||
sysctl/
|
||||
- directory with info on the /proc/sys/* files.
|
||||
target/
|
||||
- directory with info on generating TCM v4 fabric .ko modules
|
||||
tee.txt
|
||||
- info on the TEE subsystem and drivers
|
||||
this_cpu_ops.txt
|
||||
- List rationale behind and the way to use this_cpu operations.
|
||||
thermal/
|
||||
- directory with information on managing thermal issues (CPU/temp)
|
||||
trace/
|
||||
- directory with info on tracing technologies within linux
|
||||
translations/
|
||||
- translations of this document from English to another language
|
||||
unaligned-memory-access.txt
|
||||
- info on how to avoid arch breaking unaligned memory access in code.
|
||||
unshare.txt
|
||||
- description of the Linux unshare system call.
|
||||
usb/
|
||||
- directory with info regarding the Universal Serial Bus.
|
||||
vfio.txt
|
||||
- info on Virtual Function I/O used in guest/hypervisor instances.
|
||||
video-output.txt
|
||||
- sysfs class driver interface to enable/disable a video output device.
|
||||
virtual/
|
||||
- directory with information on the various linux virtualizations.
|
||||
vm/
|
||||
- directory with info on the Linux vm code.
|
||||
w1/
|
||||
- directory with documents regarding the 1-wire (w1) subsystem.
|
||||
watchdog/
|
||||
- how to auto-reboot Linux if it has "fallen and can't get up". ;-)
|
||||
wimax/
|
||||
- directory with info about Intel Wireless Wimax Connections
|
||||
core-api/workqueue.rst
|
||||
- information on the Concurrency Managed Workqueue implementation
|
||||
x86/x86_64/
|
||||
- directory with info on Linux support for AMD x86-64 (Hammer) machines.
|
||||
xillybus.txt
|
||||
- Overview and basic ui of xillybus driver
|
||||
xtensa/
|
||||
- directory with documents relating to arch/xtensa port/implementation
|
||||
xz.txt
|
||||
- how to make use of the XZ data compression within linux kernel
|
||||
zorro.txt
|
||||
- info on writing drivers for Zorro bus devices found on Amigas.
|
||||
@@ -1,26 +0,0 @@
|
||||
00-INDEX
|
||||
- this file
|
||||
acpi-info.txt
|
||||
- info on how PCI host bridges are represented in ACPI
|
||||
MSI-HOWTO.txt
|
||||
- the Message Signaled Interrupts (MSI) Driver Guide HOWTO and FAQ.
|
||||
PCIEBUS-HOWTO.txt
|
||||
- a guide describing the PCI Express Port Bus driver
|
||||
pci-error-recovery.txt
|
||||
- info on PCI error recovery
|
||||
pci-iov-howto.txt
|
||||
- the PCI Express I/O Virtualization HOWTO
|
||||
pci.txt
|
||||
- info on the PCI subsystem for device driver authors
|
||||
pcieaer-howto.txt
|
||||
- the PCI Express Advanced Error Reporting Driver Guide HOWTO
|
||||
endpoint/pci-endpoint.txt
|
||||
- guide to add endpoint controller driver and endpoint function driver.
|
||||
endpoint/pci-endpoint-cfs.txt
|
||||
- guide to use configfs to configure the PCI endpoint function.
|
||||
endpoint/pci-test-function.txt
|
||||
- specification of *PCI test* function device.
|
||||
endpoint/pci-test-howto.txt
|
||||
- userguide for PCI endpoint test function.
|
||||
endpoint/function/binding/
|
||||
- binding documentation for PCI endpoint function
|
||||
@@ -1,34 +0,0 @@
|
||||
00-INDEX
|
||||
- This file
|
||||
arrayRCU.txt
|
||||
- Using RCU to Protect Read-Mostly Arrays
|
||||
checklist.txt
|
||||
- Review Checklist for RCU Patches
|
||||
listRCU.txt
|
||||
- Using RCU to Protect Read-Mostly Linked Lists
|
||||
lockdep.txt
|
||||
- RCU and lockdep checking
|
||||
lockdep-splat.txt
|
||||
- RCU Lockdep splats explained.
|
||||
NMI-RCU.txt
|
||||
- Using RCU to Protect Dynamic NMI Handlers
|
||||
rcu_dereference.txt
|
||||
- Proper care and feeding of return values from rcu_dereference()
|
||||
rcubarrier.txt
|
||||
- RCU and Unloadable Modules
|
||||
rculist_nulls.txt
|
||||
- RCU list primitives for use with SLAB_TYPESAFE_BY_RCU
|
||||
rcuref.txt
|
||||
- Reference-count design for elements of lists/arrays protected by RCU
|
||||
rcu.txt
|
||||
- RCU Concepts
|
||||
RTFP.txt
|
||||
- List of RCU papers (bibliography) going back to 1980.
|
||||
stallwarn.txt
|
||||
- RCU CPU stall warnings (module parameter rcu_cpu_stall_suppress)
|
||||
torture.txt
|
||||
- RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)
|
||||
UP.txt
|
||||
- RCU on Uniprocessor Systems
|
||||
whatisRCU.txt
|
||||
- What is RCU?
|
||||
@@ -87,7 +87,3 @@ o Where can I find more information on RCU?
|
||||
|
||||
See the RTFP.txt file in this directory.
|
||||
Or point your browser at http://www.rdrop.com/users/paulmck/RCU/.
|
||||
|
||||
o What are all these files in this directory?
|
||||
|
||||
See 00-INDEX for the list.
|
||||
|
||||
@@ -64,8 +64,8 @@ The sysctl settings (writable only with ``CAP_SYS_PTRACE``) are:
|
||||
Using ``PTRACE_TRACEME`` is unchanged.
|
||||
|
||||
2 - admin-only attach:
|
||||
only processes with ``CAP_SYS_PTRACE`` may use ptrace
|
||||
with ``PTRACE_ATTACH``, or through children calling ``PTRACE_TRACEME``.
|
||||
only processes with ``CAP_SYS_PTRACE`` may use ptrace, either with
|
||||
``PTRACE_ATTACH`` or through children calling ``PTRACE_TRACEME``.
|
||||
|
||||
3 - no attach:
|
||||
no processes may use ptrace with ``PTRACE_ATTACH`` nor via
|
||||
|
||||
@@ -51,8 +51,7 @@ Documentation
|
||||
|
||||
- There are various README files in the Documentation/ subdirectory:
|
||||
these typically contain kernel-specific installation notes for some
|
||||
drivers for example. See Documentation/00-INDEX for a list of what
|
||||
is contained in each file. Please read the
|
||||
drivers for example. Please read the
|
||||
:ref:`Documentation/process/changes.rst <changes>` file, as it
|
||||
contains information about the problems, which may result by upgrading
|
||||
your kernel.
|
||||
|
||||
@@ -1764,7 +1764,7 @@
|
||||
Format: { "0" | "1" }
|
||||
0 - Use IOMMU translation for DMA.
|
||||
1 - Bypass the IOMMU for DMA.
|
||||
unset - Use IOMMU translation for DMA.
|
||||
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
|
||||
|
||||
io7= [HW] IO7 for Marvel based alpha systems
|
||||
See comment before marvel_specify_io7 in
|
||||
|
||||
@@ -553,7 +553,7 @@ When nested virtualization is in use, three operating systems are involved:
|
||||
the bare metal hypervisor, the nested hypervisor and the nested virtual
|
||||
machine. VMENTER operations from the nested hypervisor into the nested
|
||||
guest will always be processed by the bare metal hypervisor. If KVM is the
|
||||
bare metal hypervisor it wiil:
|
||||
bare metal hypervisor it will:
|
||||
|
||||
- Flush the L1D cache on every switch from the nested hypervisor to the
|
||||
nested virtual machine, so that the nested hypervisor's secrets are not
|
||||
|
||||
@@ -29,6 +29,7 @@ the Linux memory management.
|
||||
hugetlbpage
|
||||
idle_page_tracking
|
||||
ksm
|
||||
memory-hotplug
|
||||
numa_memory_policy
|
||||
pagemap
|
||||
soft-dirty
|
||||
|
||||
@@ -1,3 +1,5 @@
|
||||
.. _admin_guide_memory_hotplug:
|
||||
|
||||
==============
|
||||
Memory Hotplug
|
||||
==============
|
||||
@@ -9,39 +11,19 @@ This document is about memory hotplug including how-to-use and current status.
|
||||
Because Memory Hotplug is still under development, contents of this text will
|
||||
be changed often.
|
||||
|
||||
.. CONTENTS
|
||||
|
||||
1. Introduction
|
||||
1.1 purpose of memory hotplug
|
||||
1.2. Phases of memory hotplug
|
||||
1.3. Unit of Memory online/offline operation
|
||||
2. Kernel Configuration
|
||||
3. sysfs files for memory hotplug
|
||||
4. Physical memory hot-add phase
|
||||
4.1 Hardware(Firmware) Support
|
||||
4.2 Notify memory hot-add event by hand
|
||||
5. Logical Memory hot-add phase
|
||||
5.1. State of memory
|
||||
5.2. How to online memory
|
||||
6. Logical memory remove
|
||||
6.1 Memory offline and ZONE_MOVABLE
|
||||
6.2. How to offline memory
|
||||
7. Physical memory remove
|
||||
8. Memory hotplug event notifier
|
||||
9. Future Work List
|
||||
|
||||
.. contents:: :local:
|
||||
|
||||
.. note::
|
||||
|
||||
(1) x86_64's has special implementation for memory hotplug.
|
||||
This text does not describe it.
|
||||
(2) This text assumes that sysfs is mounted at /sys.
|
||||
(2) This text assumes that sysfs is mounted at ``/sys``.
|
||||
|
||||
|
||||
Introduction
|
||||
============
|
||||
|
||||
purpose of memory hotplug
|
||||
Purpose of memory hotplug
|
||||
-------------------------
|
||||
|
||||
Memory Hotplug allows users to increase/decrease the amount of memory.
|
||||
@@ -57,7 +39,6 @@ hardware which supports memory power management.
|
||||
|
||||
Linux memory hotplug is designed for both purpose.
|
||||
|
||||
|
||||
Phases of memory hotplug
|
||||
------------------------
|
||||
|
||||
@@ -92,7 +73,6 @@ phase by hand.
|
||||
(However, if you writes udev's hotplug scripts for memory hotplug, these
|
||||
phases can be execute in seamless way.)
|
||||
|
||||
|
||||
Unit of Memory online/offline operation
|
||||
---------------------------------------
|
||||
|
||||
@@ -107,10 +87,9 @@ unit upon which memory online/offline operations are to be performed. The
|
||||
default size of a memory block is the same as memory section size unless an
|
||||
architecture specifies otherwise. (see :ref:`memory_hotplug_sysfs_files`.)
|
||||
|
||||
To determine the size (in bytes) of a memory block please read this file:
|
||||
|
||||
/sys/devices/system/memory/block_size_bytes
|
||||
To determine the size (in bytes) of a memory block please read this file::
|
||||
|
||||
/sys/devices/system/memory/block_size_bytes
|
||||
|
||||
Kernel Configuration
|
||||
====================
|
||||
@@ -119,22 +98,22 @@ To use memory hotplug feature, kernel must be compiled with following
|
||||
config options.
|
||||
|
||||
- For all memory hotplug:
|
||||
- Memory model -> Sparse Memory (CONFIG_SPARSEMEM)
|
||||
- Allow for memory hot-add (CONFIG_MEMORY_HOTPLUG)
|
||||
- Memory model -> Sparse Memory (``CONFIG_SPARSEMEM``)
|
||||
- Allow for memory hot-add (``CONFIG_MEMORY_HOTPLUG``)
|
||||
|
||||
- To enable memory removal, the following are also necessary:
|
||||
- Allow for memory hot remove (CONFIG_MEMORY_HOTREMOVE)
|
||||
- Page Migration (CONFIG_MIGRATION)
|
||||
- Allow for memory hot remove (``CONFIG_MEMORY_HOTREMOVE``)
|
||||
- Page Migration (``CONFIG_MIGRATION``)
|
||||
|
||||
- For ACPI memory hotplug, the following are also necessary:
|
||||
- Memory hotplug (under ACPI Support menu) (CONFIG_ACPI_HOTPLUG_MEMORY)
|
||||
- Memory hotplug (under ACPI Support menu) (``CONFIG_ACPI_HOTPLUG_MEMORY``)
|
||||
- This option can be kernel module.
|
||||
|
||||
- As a related configuration, if your box has a feature of NUMA-node hotplug
|
||||
via ACPI, then this option is necessary too.
|
||||
|
||||
- ACPI0004,PNP0A05 and PNP0A06 Container Driver (under ACPI Support menu)
|
||||
(CONFIG_ACPI_CONTAINER).
|
||||
(``CONFIG_ACPI_CONTAINER``).
|
||||
|
||||
This option can be kernel module too.
|
||||
|
||||
@@ -145,10 +124,11 @@ sysfs files for memory hotplug
|
||||
==============================
|
||||
|
||||
All memory blocks have their device information in sysfs. Each memory block
|
||||
is described under /sys/devices/system/memory as:
|
||||
is described under ``/sys/devices/system/memory`` as::
|
||||
|
||||
/sys/devices/system/memory/memoryXXX
|
||||
(XXX is the memory block id.)
|
||||
|
||||
where XXX is the memory block id.
|
||||
|
||||
For the memory block covered by the sysfs directory. It is expected that all
|
||||
memory sections in this range are present and no memory holes exist in the
|
||||
@@ -157,7 +137,7 @@ the existence of one should not affect the hotplug capabilities of the memory
|
||||
block.
|
||||
|
||||
For example, assume 1GiB memory block size. A device for a memory starting at
|
||||
0x100000000 is /sys/device/system/memory/memory4::
|
||||
0x100000000 is ``/sys/device/system/memory/memory4``::
|
||||
|
||||
(0x100000000 / 1Gib = 4)
|
||||
|
||||
@@ -165,11 +145,11 @@ This device covers address range [0x100000000 ... 0x140000000)
|
||||
|
||||
Under each memory block, you can see 5 files:
|
||||
|
||||
- /sys/devices/system/memory/memoryXXX/phys_index
|
||||
- /sys/devices/system/memory/memoryXXX/phys_device
|
||||
- /sys/devices/system/memory/memoryXXX/state
|
||||
- /sys/devices/system/memory/memoryXXX/removable
|
||||
- /sys/devices/system/memory/memoryXXX/valid_zones
|
||||
- ``/sys/devices/system/memory/memoryXXX/phys_index``
|
||||
- ``/sys/devices/system/memory/memoryXXX/phys_device``
|
||||
- ``/sys/devices/system/memory/memoryXXX/state``
|
||||
- ``/sys/devices/system/memory/memoryXXX/removable``
|
||||
- ``/sys/devices/system/memory/memoryXXX/valid_zones``
|
||||
|
||||
=================== ============================================================
|
||||
``phys_index`` read-only and contains memory block id, same as XXX.
|
||||
@@ -207,13 +187,15 @@ Under each memory block, you can see 5 files:
|
||||
These directories/files appear after physical memory hotplug phase.
|
||||
|
||||
If CONFIG_NUMA is enabled the memoryXXX/ directories can also be accessed
|
||||
via symbolic links located in the /sys/devices/system/node/node* directories.
|
||||
via symbolic links located in the ``/sys/devices/system/node/node*`` directories.
|
||||
|
||||
For example:
|
||||
/sys/devices/system/node/node0/memory9 -> ../../memory/memory9
|
||||
For example::
|
||||
|
||||
A backlink will also be created:
|
||||
/sys/devices/system/memory/memory9/node0 -> ../../node/node0
|
||||
/sys/devices/system/node/node0/memory9 -> ../../memory/memory9
|
||||
|
||||
A backlink will also be created::
|
||||
|
||||
/sys/devices/system/memory/memory9/node0 -> ../../node/node0
|
||||
|
||||
.. _memory_hotplug_physical_mem:
|
||||
|
||||
@@ -240,7 +222,6 @@ If firmware supports NUMA-node hotplug, and defines an object _HID "ACPI0004",
|
||||
calls hotplug code for all of objects which are defined in it.
|
||||
If memory device is found, memory hotplug code will be called.
|
||||
|
||||
|
||||
Notify memory hot-add event by hand
|
||||
-----------------------------------
|
||||
|
||||
@@ -251,8 +232,9 @@ CONFIG_ARCH_MEMORY_PROBE and can be configured on powerpc, sh, and x86
|
||||
if hotplug is supported, although for x86 this should be handled by ACPI
|
||||
notification.
|
||||
|
||||
Probe interface is located at
|
||||
/sys/devices/system/memory/probe
|
||||
Probe interface is located at::
|
||||
|
||||
/sys/devices/system/memory/probe
|
||||
|
||||
You can tell the physical address of new memory to the kernel by::
|
||||
|
||||
@@ -263,7 +245,6 @@ memory_block_size] memory range is hot-added. In this case, hotplug script is
|
||||
not called (in current implementation). You'll have to online memory by
|
||||
yourself. Please see :ref:`memory_hotplug_how_to_online_memory`.
|
||||
|
||||
|
||||
Logical Memory hot-add phase
|
||||
============================
|
||||
|
||||
@@ -301,7 +282,7 @@ This sets a global policy and impacts all memory blocks that will subsequently
|
||||
be hotplugged. Currently offline blocks keep their state. It is possible, under
|
||||
certain circumstances, that some memory blocks will be added but will fail to
|
||||
online. User space tools can check their "state" files
|
||||
(/sys/devices/system/memory/memoryXXX/state) and try to online them manually.
|
||||
(``/sys/devices/system/memory/memoryXXX/state``) and try to online them manually.
|
||||
|
||||
If the automatic onlining wasn't requested, failed, or some memory block was
|
||||
offlined it is possible to change the individual block's state by writing to the
|
||||
@@ -334,8 +315,6 @@ available memory will be increased.
|
||||
|
||||
This may be changed in future.
|
||||
|
||||
|
||||
|
||||
Logical memory remove
|
||||
=====================
|
||||
|
||||
@@ -413,88 +392,6 @@ Need more implementation yet....
|
||||
- Notification completion of remove works by OS to firmware.
|
||||
- Guard from remove if not yet.
|
||||
|
||||
Memory hotplug event notifier
|
||||
=============================
|
||||
|
||||
Hotplugging events are sent to a notification queue.
|
||||
|
||||
There are six types of notification defined in include/linux/memory.h:
|
||||
|
||||
MEM_GOING_ONLINE
|
||||
Generated before new memory becomes available in order to be able to
|
||||
prepare subsystems to handle memory. The page allocator is still unable
|
||||
to allocate from the new memory.
|
||||
|
||||
MEM_CANCEL_ONLINE
|
||||
Generated if MEMORY_GOING_ONLINE fails.
|
||||
|
||||
MEM_ONLINE
|
||||
Generated when memory has successfully brought online. The callback may
|
||||
allocate pages from the new memory.
|
||||
|
||||
MEM_GOING_OFFLINE
|
||||
Generated to begin the process of offlining memory. Allocations are no
|
||||
longer possible from the memory but some of the memory to be offlined
|
||||
is still in use. The callback can be used to free memory known to a
|
||||
subsystem from the indicated memory block.
|
||||
|
||||
MEM_CANCEL_OFFLINE
|
||||
Generated if MEMORY_GOING_OFFLINE fails. Memory is available again from
|
||||
the memory block that we attempted to offline.
|
||||
|
||||
MEM_OFFLINE
|
||||
Generated after offlining memory is complete.
|
||||
|
||||
A callback routine can be registered by calling::
|
||||
|
||||
hotplug_memory_notifier(callback_func, priority)
|
||||
|
||||
Callback functions with higher values of priority are called before callback
|
||||
functions with lower values.
|
||||
|
||||
A callback function must have the following prototype::
|
||||
|
||||
int callback_func(
|
||||
struct notifier_block *self, unsigned long action, void *arg);
|
||||
|
||||
The first argument of the callback function (self) is a pointer to the block
|
||||
of the notifier chain that points to the callback function itself.
|
||||
The second argument (action) is one of the event types described above.
|
||||
The third argument (arg) passes a pointer of struct memory_notify::
|
||||
|
||||
struct memory_notify {
|
||||
unsigned long start_pfn;
|
||||
unsigned long nr_pages;
|
||||
int status_change_nid_normal;
|
||||
int status_change_nid_high;
|
||||
int status_change_nid;
|
||||
}
|
||||
|
||||
- start_pfn is start_pfn of online/offline memory.
|
||||
- nr_pages is # of pages of online/offline memory.
|
||||
- status_change_nid_normal is set node id when N_NORMAL_MEMORY of nodemask
|
||||
is (will be) set/clear, if this is -1, then nodemask status is not changed.
|
||||
- status_change_nid_high is set node id when N_HIGH_MEMORY of nodemask
|
||||
is (will be) set/clear, if this is -1, then nodemask status is not changed.
|
||||
- status_change_nid is set node id when N_MEMORY of nodemask is (will be)
|
||||
set/clear. It means a new(memoryless) node gets new memory by online and a
|
||||
node loses all memory. If this is -1, then nodemask status is not changed.
|
||||
|
||||
If status_changed_nid* >= 0, callback should create/discard structures for the
|
||||
node if necessary.
|
||||
|
||||
The callback routine shall return one of the values
|
||||
NOTIFY_DONE, NOTIFY_OK, NOTIFY_BAD, NOTIFY_STOP
|
||||
defined in include/linux/notifier.h
|
||||
|
||||
NOTIFY_DONE and NOTIFY_OK have no effect on the further processing.
|
||||
|
||||
NOTIFY_BAD is used as response to the MEM_GOING_ONLINE, MEM_GOING_OFFLINE,
|
||||
MEM_ONLINE, or MEM_OFFLINE action to cancel hotplugging. It stops
|
||||
further processing of the notification queue.
|
||||
|
||||
NOTIFY_STOP stops further processing of the notification queue.
|
||||
|
||||
Future Work
|
||||
===========
|
||||
|
||||
@@ -1,50 +0,0 @@
|
||||
00-INDEX
|
||||
- this file
|
||||
Booting
|
||||
- requirements for booting
|
||||
CCN.txt
|
||||
- Cache Coherent Network ring-bus and perf PMU driver.
|
||||
Interrupts
|
||||
- ARM Interrupt subsystem documentation
|
||||
IXP4xx
|
||||
- Intel IXP4xx Network processor.
|
||||
Netwinder
|
||||
- Netwinder specific documentation
|
||||
Porting
|
||||
- Symbol definitions for porting Linux to a new ARM machine.
|
||||
Setup
|
||||
- Kernel initialization parameters on ARM Linux
|
||||
README
|
||||
- General ARM documentation
|
||||
SA1100/
|
||||
- SA1100 documentation
|
||||
Samsung-S3C24XX/
|
||||
- S3C24XX ARM Linux Overview
|
||||
SPEAr/
|
||||
- ST SPEAr platform Linux Overview
|
||||
VFP/
|
||||
- Release notes for Linux Kernel Vector Floating Point support code
|
||||
cluster-pm-race-avoidance.txt
|
||||
- Algorithm for CPU and Cluster setup/teardown
|
||||
empeg/
|
||||
- Ltd's Empeg MP3 Car Audio Player
|
||||
firmware.txt
|
||||
- Secure firmware registration and calling.
|
||||
kernel_mode_neon.txt
|
||||
- How to use NEON instructions in kernel mode
|
||||
kernel_user_helpers.txt
|
||||
- Helper functions in kernel space made available for userspace.
|
||||
mem_alignment
|
||||
- alignment abort handler documentation
|
||||
memory.txt
|
||||
- description of the virtual memory layout
|
||||
nwfpe/
|
||||
- NWFPE floating point emulator documentation
|
||||
swp_emulation
|
||||
- SWP/SWPB emulation handler/logging description
|
||||
tcm.txt
|
||||
- ARM Tightly Coupled Memory
|
||||
uefi.txt
|
||||
- [U]EFI configuration and runtime services documentation
|
||||
vlocks.txt
|
||||
- Voting locks, low-level mechanism relying on memory system atomic writes.
|
||||
@@ -1,34 +0,0 @@
|
||||
00-INDEX
|
||||
- This file
|
||||
bfq-iosched.txt
|
||||
- BFQ IO scheduler and its tunables
|
||||
biodoc.txt
|
||||
- Notes on the Generic Block Layer Rewrite in Linux 2.5
|
||||
biovecs.txt
|
||||
- Immutable biovecs and biovec iterators
|
||||
capability.txt
|
||||
- Generic Block Device Capability (/sys/block/<device>/capability)
|
||||
cfq-iosched.txt
|
||||
- CFQ IO scheduler tunables
|
||||
cmdline-partition.txt
|
||||
- how to specify block device partitions on kernel command line
|
||||
data-integrity.txt
|
||||
- Block data integrity
|
||||
deadline-iosched.txt
|
||||
- Deadline IO scheduler tunables
|
||||
ioprio.txt
|
||||
- Block io priorities (in CFQ scheduler)
|
||||
pr.txt
|
||||
- Block layer support for Persistent Reservations
|
||||
null_blk.txt
|
||||
- Null block for block-layer benchmarking.
|
||||
queue-sysfs.txt
|
||||
- Queue's sysfs entries
|
||||
request.txt
|
||||
- The members of struct request (in include/linux/blkdev.h)
|
||||
stat.txt
|
||||
- Block layer statistics in /sys/block/<device>/stat
|
||||
switching-sched.txt
|
||||
- Switching I/O schedulers at runtime
|
||||
writeback_cache_control.txt
|
||||
- Control of volatile write back caches
|
||||
@@ -1,18 +0,0 @@
|
||||
00-INDEX
|
||||
- this file
|
||||
README.DAC960
|
||||
- info on Mylex DAC960/DAC1100 PCI RAID Controller Driver for Linux.
|
||||
cciss.txt
|
||||
- info, major/minor #'s for Compaq's SMART Array Controllers.
|
||||
cpqarray.txt
|
||||
- info on using Compaq's SMART2 Intelligent Disk Array Controllers.
|
||||
floppy.txt
|
||||
- notes and driver options for the floppy disk driver.
|
||||
mflash.txt
|
||||
- info on mGine m(g)flash driver for linux.
|
||||
nbd.txt
|
||||
- info on a TCP implementation of a network block device.
|
||||
paride.txt
|
||||
- information about the parallel port IDE subsystem.
|
||||
ramdisk.txt
|
||||
- short guide on how to set up and use the RAM disk.
|
||||
@@ -1,11 +0,0 @@
|
||||
00-INDEX
|
||||
- this file (info on CD-ROMs and Linux)
|
||||
Makefile
|
||||
- only used to generate TeX output from the documentation.
|
||||
cdrom-standard.tex
|
||||
- LaTeX document on standardizing the CD-ROM programming interface.
|
||||
ide-cd
|
||||
- info on setting up and using ATAPI (aka IDE) CD-ROMs.
|
||||
packet-writing.txt
|
||||
- Info on the CDRW packet writing module
|
||||
|
||||
@@ -1,26 +0,0 @@
|
||||
00-INDEX
|
||||
- this file
|
||||
blkio-controller.txt
|
||||
- Description for Block IO Controller, implementation and usage details.
|
||||
cgroups.txt
|
||||
- Control Groups definition, implementation details, examples and API.
|
||||
cpuacct.txt
|
||||
- CPU Accounting Controller; account CPU usage for groups of tasks.
|
||||
cpusets.txt
|
||||
- documents the cpusets feature; assign CPUs and Mem to a set of tasks.
|
||||
admin-guide/devices.rst
|
||||
- Device Whitelist Controller; description, interface and security.
|
||||
freezer-subsystem.txt
|
||||
- checkpointing; rationale to not use signals, interface.
|
||||
hugetlb.txt
|
||||
- HugeTLB Controller implementation and usage details.
|
||||
memcg_test.txt
|
||||
- Memory Resource Controller; implementation details.
|
||||
memory.txt
|
||||
- Memory Resource Controller; design, accounting, interface, testing.
|
||||
net_cls.txt
|
||||
- Network classifier cgroups details and usages.
|
||||
net_prio.txt
|
||||
- Network priority cgroups details and usages.
|
||||
pids.txt
|
||||
- Process number cgroups details and usages.
|
||||
@@ -259,7 +259,7 @@ latex_elements = {
|
||||
'papersize': 'a4paper',
|
||||
|
||||
# The font size ('10pt', '11pt' or '12pt').
|
||||
'pointsize': '8pt',
|
||||
'pointsize': '11pt',
|
||||
|
||||
# Latex figure (float) alignment
|
||||
#'figure_align': 'htbp',
|
||||
@@ -272,8 +272,8 @@ latex_elements = {
|
||||
'preamble': '''
|
||||
% Use some font with UTF-8 support with XeLaTeX
|
||||
\\usepackage{fontspec}
|
||||
\\setsansfont{DejaVu Serif}
|
||||
\\setromanfont{DejaVu Sans}
|
||||
\\setsansfont{DejaVu Sans}
|
||||
\\setromanfont{DejaVu Serif}
|
||||
\\setmonofont{DejaVu Sans Mono}
|
||||
|
||||
'''
|
||||
|
||||
@@ -76,7 +76,7 @@ These interfaces available only with bootmem, i.e when ``CONFIG_NO_BOOTMEM=n``
|
||||
|
||||
.. kernel-doc:: include/linux/bootmem.h
|
||||
.. kernel-doc:: mm/bootmem.c
|
||||
:nodocs:
|
||||
:functions:
|
||||
|
||||
Memblock specific API
|
||||
---------------------
|
||||
@@ -89,4 +89,4 @@ really happens under the hood.
|
||||
|
||||
.. kernel-doc:: include/linux/memblock.h
|
||||
.. kernel-doc:: mm/memblock.c
|
||||
:nodocs:
|
||||
:functions:
|
||||
|
||||
@@ -1,3 +1,5 @@
|
||||
.. _gfp_mask_from_fs_io:
|
||||
|
||||
=================================
|
||||
GFP masks used from FS/IO context
|
||||
=================================
|
||||
|
||||
@@ -27,10 +27,13 @@ Core utilities
|
||||
errseq
|
||||
printk-formats
|
||||
circular-buffers
|
||||
memory-allocation
|
||||
mm-api
|
||||
gfp_mask-from-fs-io
|
||||
timekeeping
|
||||
boot-time-mm
|
||||
memory-hotplug
|
||||
|
||||
|
||||
Interfaces for kernel debugging
|
||||
===============================
|
||||
|
||||
122
Documentation/core-api/memory-allocation.rst
Normal file
122
Documentation/core-api/memory-allocation.rst
Normal file
@@ -0,0 +1,122 @@
|
||||
=======================
|
||||
Memory Allocation Guide
|
||||
=======================
|
||||
|
||||
Linux provides a variety of APIs for memory allocation. You can
|
||||
allocate small chunks using `kmalloc` or `kmem_cache_alloc` families,
|
||||
large virtually contiguous areas using `vmalloc` and its derivatives,
|
||||
or you can directly request pages from the page allocator with
|
||||
`alloc_pages`. It is also possible to use more specialized allocators,
|
||||
for instance `cma_alloc` or `zs_malloc`.
|
||||
|
||||
Most of the memory allocation APIs use GFP flags to express how that
|
||||
memory should be allocated. The GFP acronym stands for "get free
|
||||
pages", the underlying memory allocation function.
|
||||
|
||||
Diversity of the allocation APIs combined with the numerous GFP flags
|
||||
makes the question "How should I allocate memory?" not that easy to
|
||||
answer, although very likely you should use
|
||||
|
||||
::
|
||||
|
||||
kzalloc(<size>, GFP_KERNEL);
|
||||
|
||||
Of course there are cases when other allocation APIs and different GFP
|
||||
flags must be used.
|
||||
|
||||
Get Free Page flags
|
||||
===================
|
||||
|
||||
The GFP flags control the allocators behavior. They tell what memory
|
||||
zones can be used, how hard the allocator should try to find free
|
||||
memory, whether the memory can be accessed by the userspace etc. The
|
||||
:ref:`Documentation/core-api/mm-api.rst <mm-api-gfp-flags>` provides
|
||||
reference documentation for the GFP flags and their combinations and
|
||||
here we briefly outline their recommended usage:
|
||||
|
||||
* Most of the time ``GFP_KERNEL`` is what you need. Memory for the
|
||||
kernel data structures, DMAable memory, inode cache, all these and
|
||||
many other allocations types can use ``GFP_KERNEL``. Note, that
|
||||
using ``GFP_KERNEL`` implies ``GFP_RECLAIM``, which means that
|
||||
direct reclaim may be triggered under memory pressure; the calling
|
||||
context must be allowed to sleep.
|
||||
* If the allocation is performed from an atomic context, e.g interrupt
|
||||
handler, use ``GFP_NOWAIT``. This flag prevents direct reclaim and
|
||||
IO or filesystem operations. Consequently, under memory pressure
|
||||
``GFP_NOWAIT`` allocation is likely to fail. Allocations which
|
||||
have a reasonable fallback should be using ``GFP_NOWARN``.
|
||||
* If you think that accessing memory reserves is justified and the kernel
|
||||
will be stressed unless allocation succeeds, you may use ``GFP_ATOMIC``.
|
||||
* Untrusted allocations triggered from userspace should be a subject
|
||||
of kmem accounting and must have ``__GFP_ACCOUNT`` bit set. There
|
||||
is the handy ``GFP_KERNEL_ACCOUNT`` shortcut for ``GFP_KERNEL``
|
||||
allocations that should be accounted.
|
||||
* Userspace allocations should use either of the ``GFP_USER``,
|
||||
``GFP_HIGHUSER`` or ``GFP_HIGHUSER_MOVABLE`` flags. The longer
|
||||
the flag name the less restrictive it is.
|
||||
|
||||
``GFP_HIGHUSER_MOVABLE`` does not require that allocated memory
|
||||
will be directly accessible by the kernel and implies that the
|
||||
data is movable.
|
||||
|
||||
``GFP_HIGHUSER`` means that the allocated memory is not movable,
|
||||
but it is not required to be directly accessible by the kernel. An
|
||||
example may be a hardware allocation that maps data directly into
|
||||
userspace but has no addressing limitations.
|
||||
|
||||
``GFP_USER`` means that the allocated memory is not movable and it
|
||||
must be directly accessible by the kernel.
|
||||
|
||||
You may notice that quite a few allocations in the existing code
|
||||
specify ``GFP_NOIO`` or ``GFP_NOFS``. Historically, they were used to
|
||||
prevent recursion deadlocks caused by direct memory reclaim calling
|
||||
back into the FS or IO paths and blocking on already held
|
||||
resources. Since 4.12 the preferred way to address this issue is to
|
||||
use new scope APIs described in
|
||||
:ref:`Documentation/core-api/gfp_mask-from-fs-io.rst <gfp_mask_from_fs_io>`.
|
||||
|
||||
Other legacy GFP flags are ``GFP_DMA`` and ``GFP_DMA32``. They are
|
||||
used to ensure that the allocated memory is accessible by hardware
|
||||
with limited addressing capabilities. So unless you are writing a
|
||||
driver for a device with such restrictions, avoid using these flags.
|
||||
And even with hardware with restrictions it is preferable to use
|
||||
`dma_alloc*` APIs.
|
||||
|
||||
Selecting memory allocator
|
||||
==========================
|
||||
|
||||
The most straightforward way to allocate memory is to use a function
|
||||
from the :c:func:`kmalloc` family. And, to be on the safe size it's
|
||||
best to use routines that set memory to zero, like
|
||||
:c:func:`kzalloc`. If you need to allocate memory for an array, there
|
||||
are :c:func:`kmalloc_array` and :c:func:`kcalloc` helpers.
|
||||
|
||||
The maximal size of a chunk that can be allocated with `kmalloc` is
|
||||
limited. The actual limit depends on the hardware and the kernel
|
||||
configuration, but it is a good practice to use `kmalloc` for objects
|
||||
smaller than page size.
|
||||
|
||||
For large allocations you can use :c:func:`vmalloc` and
|
||||
:c:func:`vzalloc`, or directly request pages from the page
|
||||
allocator. The memory allocated by `vmalloc` and related functions is
|
||||
not physically contiguous.
|
||||
|
||||
If you are not sure whether the allocation size is too large for
|
||||
`kmalloc`, it is possible to use :c:func:`kvmalloc` and its
|
||||
derivatives. It will try to allocate memory with `kmalloc` and if the
|
||||
allocation fails it will be retried with `vmalloc`. There are
|
||||
restrictions on which GFP flags can be used with `kvmalloc`; please
|
||||
see :c:func:`kvmalloc_node` reference documentation. Note that
|
||||
`kvmalloc` may return memory that is not physically contiguous.
|
||||
|
||||
If you need to allocate many identical objects you can use the slab
|
||||
cache allocator. The cache should be set up with
|
||||
:c:func:`kmem_cache_create` before it can be used. Afterwards
|
||||
:c:func:`kmem_cache_alloc` and its convenience wrappers can allocate
|
||||
memory from that cache.
|
||||
|
||||
When the allocated memory is no longer needed it must be freed. You
|
||||
can use :c:func:`kvfree` for the memory allocated with `kmalloc`,
|
||||
`vmalloc` and `kvmalloc`. The slab caches should be freed with
|
||||
:c:func:`kmem_cache_free`. And don't forget to destroy the cache with
|
||||
:c:func:`kmem_cache_destroy`.
|
||||
Some files were not shown because too many files have changed in this diff Show More
Reference in New Issue
Block a user