See also Documentation/fault-injection/.
floppy= [HW]
- See Documentation/blockdev/floppy.txt.
+ See Documentation/blockdev/floppy.rst.
force_pal_cache_flush
[IA-64] Avoid check_sal_cache_flush which may hang on
memblock=debug [KNL] Enable memblock debug messages.
load_ramdisk= [RAM] List of ramdisks to load from floppy
- See Documentation/blockdev/ramdisk.txt.
+ See Documentation/blockdev/ramdisk.rst.
lockd.nlm_grace_period=P [NFS] Assign grace period.
Format: <integer>
pcd. [PARIDE]
See header of drivers/block/paride/pcd.c.
- See also Documentation/blockdev/paride.txt.
+ See also Documentation/blockdev/paride.rst.
pci=option[,option...] [PCI] various PCI subsystem options.
needed on a platform with proper driver support.
pd. [PARIDE]
- See Documentation/blockdev/paride.txt.
+ See Documentation/blockdev/paride.rst.
pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
boot time.
and performance comparison.
pf. [PARIDE]
- See Documentation/blockdev/paride.txt.
+ See Documentation/blockdev/paride.rst.
pg. [PARIDE]
- See Documentation/blockdev/paride.txt.
+ See Documentation/blockdev/paride.rst.
pirq= [SMP,APIC] Manual mp-table setup
See Documentation/x86/i386/IO-APIC.rst.
prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
before loading.
- See Documentation/blockdev/ramdisk.txt.
+ See Documentation/blockdev/ramdisk.rst.
psi= [KNL] Enable or disable pressure stall information
tracking.
pstore.backend= Specify the name of the pstore backend to use
pt. [PARIDE]
- See Documentation/blockdev/paride.txt.
+ See Documentation/blockdev/paride.rst.
pti= [X86_64] Control Page Table Isolation of user and
kernel address spaces. Disabling this feature
See Documentation/admin-guide/md.rst.
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
- See Documentation/blockdev/ramdisk.txt.
+ See Documentation/blockdev/ramdisk.rst.
random.trust_cpu={on,off}
[KNL] Enable or disable trusting the use of the
+================================
+kernel data structure for DRBD-9
+================================
+
This describes the in kernel data structure for DRBD-9. Starting with
Linux v3.14 we are reorganizing DRBD to use this data structure.
The DRBD objects are interconnected to form a matrix as depicted below; a
drbd_peer_device object sits at each intersection between a drbd_device and a
-drbd_connection:
+drbd_connection::
/--------------+---------------+.....+---------------\
| resource | device | | device |
--- /dev/null
+.. The here included files are intended to help understand the implementation
+
+Data flows that Relate some functions, and write packets
+========================================================
+
+.. kernel-figure:: DRBD-8.3-data-packets.svg
+ :alt: DRBD-8.3-data-packets.svg
+ :align: center
+
+.. kernel-figure:: DRBD-data-packets.svg
+ :alt: DRBD-data-packets.svg
+ :align: center
+
+
+Sub graphs of DRBD's state transitions
+======================================
+
+.. kernel-figure:: conn-states-8.dot
+ :alt: conn-states-8.dot
+ :align: center
+
+.. kernel-figure:: disk-states-8.dot
+ :alt: disk-states-8.dot
+ :align: center
+
+.. kernel-figure:: node-states-8.dot
+ :alt: node-states-8.dot
+ :align: center
+==========================================
+Distributed Replicated Block Device - DRBD
+==========================================
+
Description
+===========
DRBD is a shared-nothing, synchronously replicated block device. It
is designed to serve as a building block for high availability
Please visit http://www.drbd.org to find out more.
-The here included files are intended to help understand the implementation
-
-DRBD-8.3-data-packets.svg, DRBD-data-packets.svg
- relates some functions, and write packets.
+.. toctree::
+ :maxdepth: 1
-conn-states-8.dot, disk-states-8.dot, node-states-8.dot
- The sub graphs of DRBD's state transitions
+ data-structure-v9
+ figures
-This file describes the floppy driver.
+=============
+Floppy Driver
+=============
FAQ list:
=========
- A FAQ list may be found in the fdutils package (see below), and also
+A FAQ list may be found in the fdutils package (see below), and also
at <http://fdutils.linux.lu/faq.html>.
LILO configuration options (Thinkpad users, read this)
======================================================
- The floppy driver is configured using the 'floppy=' option in
+The floppy driver is configured using the 'floppy=' option in
lilo. This option can be typed at the boot prompt, or entered in the
lilo configuration file.
- Example: If your kernel is called linux-2.6.9, type the following line
-at the lilo boot prompt (if you have a thinkpad):
+Example: If your kernel is called linux-2.6.9, type the following line
+at the lilo boot prompt (if you have a thinkpad)::
linux-2.6.9 floppy=thinkpad
You may also enter the following line in /etc/lilo.conf, in the description
-of linux-2.6.9:
+of linux-2.6.9::
append = "floppy=thinkpad"
- Several floppy related options may be given, example:
+Several floppy related options may be given, example::
linux-2.6.9 floppy=daring floppy=two_fdc
append = "floppy=daring floppy=two_fdc"
- If you give options both in the lilo config file and on the boot
+If you give options both in the lilo config file and on the boot
prompt, the option strings of both places are concatenated, the boot
prompt options coming last. That's why there are also options to
restore the default behavior.
Module configuration options
============================
- If you use the floppy driver as a module, use the following syntax:
-modprobe floppy floppy="<options>"
+If you use the floppy driver as a module, use the following syntax::
-Example:
- modprobe floppy floppy="omnibook messages"
+ modprobe floppy floppy="<options>"
- If you need certain options enabled every time you load the floppy driver,
-you can put:
+Example::
- options floppy floppy="omnibook messages"
+ modprobe floppy floppy="omnibook messages"
+
+If you need certain options enabled every time you load the floppy driver,
+you can put::
+
+ options floppy floppy="omnibook messages"
in a configuration file in /etc/modprobe.d/.
- The floppy driver related options are:
+The floppy driver related options are:
floppy=asus_pci
Sets the bit mask to allow only units 0 and 1. (default)
Tells the floppy driver that you have only one floppy controller.
(default)
- floppy=two_fdc
- floppy=<address>,two_fdc
+ floppy=two_fdc / floppy=<address>,two_fdc
Tells the floppy driver that you have two floppy controllers.
The second floppy controller is assumed to be at <address>.
This option is not needed if the second controller is at address
floppy=0,thinkpad
Tells the floppy driver that you don't have a Thinkpad.
- floppy=omnibook
- floppy=nodma
+ floppy=omnibook / floppy=nodma
Tells the floppy driver not to use Dma for data transfers.
This is needed on HP Omnibooks, which don't have a workable
DMA channel for the floppy driver. This option is also useful
described in the physical CMOS), or if your BIOS uses
non-standard CMOS types. The CMOS types are:
- 0 - Use the value of the physical CMOS
- 1 - 5 1/4 DD
- 2 - 5 1/4 HD
- 3 - 3 1/2 DD
- 4 - 3 1/2 HD
- 5 - 3 1/2 ED
- 6 - 3 1/2 ED
- 16 - unknown or not installed
+ == ==================================
+ 0 Use the value of the physical CMOS
+ 1 5 1/4 DD
+ 2 5 1/4 HD
+ 3 3 1/2 DD
+ 4 3 1/2 HD
+ 5 3 1/2 ED
+ 6 3 1/2 ED
+ 16 unknown or not installed
+ == ==================================
(Note: there are two valid types for ED drives. This is because 5 was
initially chosen to represent floppy *tapes*, and 6 for ED drives.
Print a warning message when an unexpected interrupt is received.
(default)
- floppy=no_unexpected_interrupts
- floppy=L40SX
+ floppy=no_unexpected_interrupts / floppy=L40SX
Don't print a message when an unexpected interrupt is received. This
is needed on IBM L40SX laptops in certain video modes. (There seems
to be an interaction between video and floppy. The unexpected
Sets the floppy DMA channel to <nr> instead of 2.
floppy=slow
- Use PS/2 stepping rate:
- " PS/2 floppies have much slower step rates than regular floppies.
+ Use PS/2 stepping rate::
+
+ PS/2 floppies have much slower step rates than regular floppies.
It's been recommended that take about 1/4 of the default speed
- in some more extreme cases."
+ in some more extreme cases.
Supporting utilities and additional documentation:
==================================================
- Additional parameters of the floppy driver can be configured at
+Additional parameters of the floppy driver can be configured at
runtime. Utilities which do this can be found in the fdutils package.
This package also contains a new version of mtools which allows to
access high capacity disks (up to 1992K on a high density 3 1/2 disk!).
It also contains additional documentation about the floppy driver.
The latest version can be found at fdutils homepage:
+
http://fdutils.linux.lu
The fdutils releases can be found at:
+
http://fdutils.linux.lu/download.html
+
http://www.tux.org/pub/knaff/fdutils/
+
ftp://metalab.unc.edu/pub/Linux/utils/disk-management/
Reporting problems about the floppy driver
==========================================
- If you have a question or a bug report about the floppy driver, mail
+If you have a question or a bug report about the floppy driver, mail
me at Alain.Knaff@poboxes.com . If you post to Usenet, preferably use
comp.os.linux.hardware. As the volume in these groups is rather high,
be sure to include the word "floppy" (or "FLOPPY") in the subject
line. If the reported problem happens when mounting floppy disks, be
sure to mention also the type of the filesystem in the subject line.
- Be sure to read the FAQ before mailing/posting any bug reports!
+Be sure to read the FAQ before mailing/posting any bug reports!
- Alain
+Alain
Changelog
=========
-10-30-2004 : Cleanup, updating, add reference to module configuration.
+10-30-2004 :
+ Cleanup, updating, add reference to module configuration.
James Nelson <james4765@gmail.com>
-6-3-2000 : Original Document
+6-3-2000 :
+ Original Document
--- /dev/null
+:orphan:
+
+===========================
+The Linux RapidIO Subsystem
+===========================
+
+.. toctree::
+ :maxdepth: 1
+
+ floppy
+ nbd
+ paride
+ ramdisk
+ zram
+
+ drbd/index
+==================================
Network Block Device (TCP version)
==================================
nbds_max
Number of block devices that should be initialized (default: 16).
-
-
- Linux and parallel port IDE devices
+===================================
+Linux and parallel port IDE devices
+===================================
PARIDE v1.03 (c) 1997-8 Grant Guenther <grant@torque.net>
1. Introduction
+===============
Owing to the simplicity and near universality of the parallel port interface
to personal computers, many external devices such as portable hard-disk,
CD-ROM, LS-120 and tape drives use the parallel port to connect to their
host computer. While some devices (notably scanners) use ad-hoc methods
-to pass commands and data through the parallel port interface, most
+to pass commands and data through the parallel port interface, most
external devices are actually identical to an internal model, but with
a parallel-port adapter chip added in. Some of the original parallel port
adapters were little more than mechanisms for multiplexing a SCSI bus.
find a standard ATAPI CD-ROM drive, a power supply, and a single adapter
that interconnected a standard PC parallel port cable and a standard
IDE cable. It is usually possible to exchange the CD-ROM device with
-any other device using the IDE interface.
+any other device using the IDE interface.
The document describes the support in Linux for parallel port IDE
devices. It does not cover parallel port SCSI devices, "ditto" tape
-drives or scanners. Many different devices are supported by the
+drives or scanners. Many different devices are supported by the
parallel port IDE subsystem, including:
- MicroSolutions backpack CD-ROM
- MicroSolutions backpack PD/CD
- MicroSolutions backpack hard-drives
- MicroSolutions backpack 8000t tape drive
- SyQuest EZ-135, EZ-230 & SparQ drives
- Avatar Shark
- Imation Superdisk LS-120
- Maxell Superdisk LS-120
- FreeCom Power CD
- Hewlett-Packard 5GB and 8GB tape drives
- Hewlett-Packard 7100 and 7200 CD-RW drives
+ - MicroSolutions backpack CD-ROM
+ - MicroSolutions backpack PD/CD
+ - MicroSolutions backpack hard-drives
+ - MicroSolutions backpack 8000t tape drive
+ - SyQuest EZ-135, EZ-230 & SparQ drives
+ - Avatar Shark
+ - Imation Superdisk LS-120
+ - Maxell Superdisk LS-120
+ - FreeCom Power CD
+ - Hewlett-Packard 5GB and 8GB tape drives
+ - Hewlett-Packard 7100 and 7200 CD-RW drives
as well as most of the clone and no-name products on the market.
To support such a wide range of devices, PARIDE, the parallel port IDE
subsystem, is actually structured in three parts. There is a base
paride module which provides a registry and some common methods for
-accessing the parallel ports. The second component is a set of
-high-level drivers for each of the different types of supported devices:
+accessing the parallel ports. The second component is a set of
+high-level drivers for each of the different types of supported devices:
+ === =============
pd IDE disk
pcd ATAPI CD-ROM
pf ATAPI disk
pt ATAPI tape
pg ATAPI generic
+ === =============
(Currently, the pg driver is only used with CD-R drives).
The high-level drivers function according to the relevant standards.
The third component of PARIDE is a set of low-level protocol drivers
for each of the parallel port IDE adapter chips. Thanks to the interest
-and encouragement of Linux users from many parts of the world,
+and encouragement of Linux users from many parts of the world,
support is available for almost all known adapter protocols:
+ ==== ====================================== ====
aten ATEN EH-100 (HK)
bpck Microsolutions backpack (US)
comm DataStor (old-type) "commuter" adapter (TW)
ktti KT Technology PHd adapter (SG)
on20 OnSpec 90c20 (US)
on26 OnSpec 90c26 (US)
+ ==== ====================================== ====
2. Using the PARIDE subsystem
+=============================
While configuring the Linux kernel, you may choose either to build
the PARIDE drivers into your kernel, or to build them as modules.
as well as at least one of the high-level drivers and at least one
of the parallel port communication protocols. If you do not know
what kind of parallel port adapter is used in your drive, you could
-begin by checking the file names and any text files on your DOS
+begin by checking the file names and any text files on your DOS
installation floppy. Alternatively, you can look at the markings on
the adapter chip itself. That's usually sufficient to identify the
-correct device.
+correct device.
You can actually select all the protocol modules, and allow the PARIDE
subsystem to try them all for you.
For the "brand-name" products listed above, here are the protocol
and high-level drivers that you would use:
+ ================ ============ ====== ========
Manufacturer Model Driver Protocol
-
+ ================ ============ ====== ========
MicroSolutions CD-ROM pcd bpck
MicroSolutions PD drive pf bpck
MicroSolutions hard-drive pd bpck
Hewlett-Packard 5GB Tape pt epat
Hewlett-Packard 7200e (CD) pcd epat
Hewlett-Packard 7200e (CD-R) pg epat
+ ================ ============ ====== ========
2.1 Configuring built-in drivers
+---------------------------------
We recommend that you get to know how the drivers work and how to
configure them as loadable modules, before attempting to compile a
chain ID. While your system is booting, a number of messages are
displayed on the console. Like all such messages, they can be
reviewed with the 'dmesg' command. Among those messages will be
-some lines like:
+some lines like::
paride: bpck registered as protocol 0
paride: epat registered as protocol 1
documentation about this).
As an example, let's assume that you have a MicroSolutions PD/CD drive
-with unit ID number 36 connected to the parallel port at 0x378, a SyQuest
-EZ-135 connected to the chained port on the PD/CD drive and also an
-Imation Superdisk connected to port 0x278. You could give the following
-options on your boot command:
+with unit ID number 36 connected to the parallel port at 0x378, a SyQuest
+EZ-135 connected to the chained port on the PD/CD drive and also an
+Imation Superdisk connected to port 0x278. You could give the following
+options on your boot command::
pd.drive0=0x378,1 pf.drive0=0x278,1 pf.drive1=0x378,0,36
is the parallel port base address, the 0 is the protocol registration
number and 36 is the chain ID.
-Please note: while PARIDE will work both with and without the
+Please note: while PARIDE will work both with and without the
PARPORT parallel port sharing system that is included by the
"Parallel port support" option, PARPORT must be included and enabled
if you want to use chains of devices on the same parallel port.
2.2 Loading and configuring PARIDE as modules
+----------------------------------------------
It is much faster and simpler to get to understand the PARIDE drivers
-if you use them as loadable kernel modules.
+if you use them as loadable kernel modules.
-Note 1: using these drivers with the "kerneld" automatic module loading
-system is not recommended for beginners, and is not documented here.
+Note 1:
+ using these drivers with the "kerneld" automatic module loading
+ system is not recommended for beginners, and is not documented here.
-Note 2: if you build PARPORT support as a loadable module, PARIDE must
-also be built as loadable modules, and PARPORT must be loaded before the
-PARIDE modules.
+Note 2:
+ if you build PARPORT support as a loadable module, PARIDE must
+ also be built as loadable modules, and PARPORT must be loaded before
+ the PARIDE modules.
-To use PARIDE, you must begin by
+To use PARIDE, you must begin by::
insmod paride
Then, load as many of the protocol modules as you think you might need.
As you load each module, it will register the protocols that it supports,
-and print a log message to your kernel log file and your console. For
-example:
+and print a log message to your kernel log file and your console. For
+example::
# insmod epat
paride: epat registered as protocol 0
paride: k971 registered as protocol 2
Finally, you can load high-level drivers for each kind of device that
-you have connected. By default, each driver will autoprobe for a single
+you have connected. By default, each driver will autoprobe for a single
device, but you can support up to four similar devices by giving their
individual co-ordinates when you load the driver.
For example, if you had two no-name CD-ROM drives both using the
KingByte KBIC-951A adapter, one on port 0x378 and the other on 0x3bc
-you could give the following command:
+you could give the following command::
# insmod pcd drive0=0x378,1 drive1=0x3bc,1
For most adapters, giving a port address and protocol number is sufficient,
-but check the source files in linux/drivers/block/paride for more
+but check the source files in linux/drivers/block/paride for more
information. (Hopefully someone will write some man pages one day !).
As another example, here's what happens when PARPORT is installed, and
-a SyQuest EZ-135 is attached to port 0x378:
+a SyQuest EZ-135 is attached to port 0x378::
# insmod paride
paride: version 1.0 installed
scanner - in this case it reports that it has found a disk with one partition.
2.3 Using a PARIDE device
+--------------------------
Once the drivers have been loaded, you can access PARIDE devices in the
same way as their traditional counterparts. You will probably need to
create the device "special files". Here is a simple script that you can
-cut to a file and execute:
-
-#!/bin/bash
-#
-# mkd -- a script to create the device special files for the PARIDE subsystem
-#
-function mkdev {
- mknod $1 $2 $3 $4 ; chmod 0660 $1 ; chown root:disk $1
-}
-#
-function pd {
- D=$( printf \\$( printf "x%03x" $[ $1 + 97 ] ) )
- mkdev pd$D b 45 $[ $1 * 16 ]
- for P in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
- do mkdev pd$D$P b 45 $[ $1 * 16 + $P ]
- done
-}
-#
-cd /dev
-#
-for u in 0 1 2 3 ; do pd $u ; done
-for u in 0 1 2 3 ; do mkdev pcd$u b 46 $u ; done
-for u in 0 1 2 3 ; do mkdev pf$u b 47 $u ; done
-for u in 0 1 2 3 ; do mkdev pt$u c 96 $u ; done
-for u in 0 1 2 3 ; do mkdev npt$u c 96 $[ $u + 128 ] ; done
-for u in 0 1 2 3 ; do mkdev pg$u c 97 $u ; done
-#
-# end of mkd
+cut to a file and execute::
+
+ #!/bin/bash
+ #
+ # mkd -- a script to create the device special files for the PARIDE subsystem
+ #
+ function mkdev {
+ mknod $1 $2 $3 $4 ; chmod 0660 $1 ; chown root:disk $1
+ }
+ #
+ function pd {
+ D=$( printf \\$( printf "x%03x" $[ $1 + 97 ] ) )
+ mkdev pd$D b 45 $[ $1 * 16 ]
+ for P in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
+ do mkdev pd$D$P b 45 $[ $1 * 16 + $P ]
+ done
+ }
+ #
+ cd /dev
+ #
+ for u in 0 1 2 3 ; do pd $u ; done
+ for u in 0 1 2 3 ; do mkdev pcd$u b 46 $u ; done
+ for u in 0 1 2 3 ; do mkdev pf$u b 47 $u ; done
+ for u in 0 1 2 3 ; do mkdev pt$u c 96 $u ; done
+ for u in 0 1 2 3 ; do mkdev npt$u c 96 $[ $u + 128 ] ; done
+ for u in 0 1 2 3 ; do mkdev pg$u c 97 $u ; done
+ #
+ # end of mkd
With the device files and drivers in place, you can access PARIDE devices
-like any other Linux device. For example, to mount a CD-ROM in pcd0, use:
+like any other Linux device. For example, to mount a CD-ROM in pcd0, use::
mount /dev/pcd0 /cdrom
If you have a fresh Avatar Shark cartridge, and the drive is pda, you
-might do something like:
+might do something like::
fdisk /dev/pda -- make a new partition table with
partition 1 of type 83
Devices like the Imation superdisk work in the same way, except that
they do not have a partition table. For example to make a 120MB
-floppy that you could share with a DOS system:
+floppy that you could share with a DOS system::
mkdosfs /dev/pf0
mount /dev/pf0 /mnt
2.4 The pf driver
+------------------
The pf driver is intended for use with parallel port ATAPI disk
devices. The most common devices in this category are PD drives
and LS-120 drives. Traditionally, media for these devices are not
partitioned. Consequently, the pf driver does not support partitioned
-media. This may be changed in a future version of the driver.
+media. This may be changed in a future version of the driver.
2.5 Using the pt driver
+------------------------
The pt driver for parallel port ATAPI tape drives is a minimal driver.
-It does not yet support many of the standard tape ioctl operations.
+It does not yet support many of the standard tape ioctl operations.
For best performance, a block size of 32KB should be used. You will
probably want to set the parallel port delay to 0, if you can.
2.6 Using the pg driver
+------------------------
The pg driver can be used in conjunction with the cdrecord program
to create CD-ROMs. Please get cdrecord version 1.6.1 or later
-from ftp://ftp.fokus.gmd.de/pub/unix/cdrecord/ . To record CD-R media
-your parallel port should ideally be set to EPP mode, and the "port delay"
-should be set to 0. With those settings it is possible to record at 2x
+from ftp://ftp.fokus.gmd.de/pub/unix/cdrecord/ . To record CD-R media
+your parallel port should ideally be set to EPP mode, and the "port delay"
+should be set to 0. With those settings it is possible to record at 2x
speed without any buffer underruns. If you cannot get the driver to work
in EPP mode, try to use "bidirectional" or "PS/2" mode and 1x speeds only.
3. Troubleshooting
+==================
3.1 Use EPP mode if you can
+----------------------------
The most common problems that people report with the PARIDE drivers
concern the parallel port CMOS settings. At this time, none of the
using your CMOS setup procedure.
3.2 Check the port delay
+-------------------------
Some parallel ports cannot reliably transfer data at full speed. To
offset the errors, the PARIDE protocol modules introduce a "port
linux/drivers/block/paride.
3.3 Some drives need a printer reset
+-------------------------------------
There appear to be a number of "noname" external drives on the market
that do not always power up correctly. We have noticed this with some
drives based on OnSpec and older Freecom adapters. In these rare cases,
the adapter can often be reinitialised by issuing a "printer reset" on
-the parallel port. As the reset operation is potentially disruptive in
-multiple device environments, the PARIDE drivers will not do it
-automatically. You can however, force a printer reset by doing:
+the parallel port. As the reset operation is potentially disruptive in
+multiple device environments, the PARIDE drivers will not do it
+automatically. You can however, force a printer reset by doing::
insmod lp reset=1
rmmod lp
If you have one of these marginal cases, you should probably build
your paride drivers as modules, and arrange to do the printer reset
-before loading the PARIDE drivers.
+before loading the PARIDE drivers.
3.4 Use the verbose option and dmesg if you need help
+------------------------------------------------------
While a lot of testing has gone into these drivers to make them work
as smoothly as possible, problems will arise. If you do have problems,
and that either (a) PARPORT is enabled or (b) no other device driver
is using your parallel port (check in /proc/ioports). Then, load the
appropriate drivers (you can load several protocol modules if you want)
-as in:
+as in::
# insmod paride
# insmod epat
and post your report there.
3.5 For more information or help
+---------------------------------
You can join the linux-parport mailing list by sending a mail message
-to
+to:
+
linux-parport-request@torque.net
-with the single word
+with the single word::
subscribe
You might also find some useful information on the linux-parport
web pages (although they are not always up to date) at
- http://web.archive.org/web/*/http://www.torque.net/parport/
-
-
+ http://web.archive.org/web/%2E/http://www.torque.net/parport/
+==========================================
Using the RAM disk block device with Linux
-------------------------------------------
+==========================================
-Contents:
+.. Contents:
1) Overview
2) Kernel Command Line Parameters
2a) Kernel Command Line Parameters
ramdisk_size=N
- ==============
+ Size of the ramdisk.
This parameter tells the RAM disk driver to set up RAM disks of N k size. The
default is 4096 (4 MB).
2b) Module parameters
rd_nr
- =====
- /dev/ramX devices created.
+ /dev/ramX devices created.
max_part
- ========
- Maximum partition number.
+ Maximum partition number.
rd_size
- =======
- See ramdisk_size.
+ See ramdisk_size.
3) Using "rdev -r"
------------------
prompt/wait sequence is to be given before trying to read the RAM disk. Since
the RAM disk dynamically grows as data is being written into it, a size field
is not required. Bits 11 to 13 are not currently used and may as well be zero.
-These numbers are no magical secrets, as seen below:
+These numbers are no magical secrets, as seen below::
-./arch/x86/kernel/setup.c:#define RAMDISK_IMAGE_START_MASK 0x07FF
-./arch/x86/kernel/setup.c:#define RAMDISK_PROMPT_FLAG 0x8000
-./arch/x86/kernel/setup.c:#define RAMDISK_LOAD_FLAG 0x4000
+ ./arch/x86/kernel/setup.c:#define RAMDISK_IMAGE_START_MASK 0x07FF
+ ./arch/x86/kernel/setup.c:#define RAMDISK_PROMPT_FLAG 0x8000
+ ./arch/x86/kernel/setup.c:#define RAMDISK_LOAD_FLAG 0x4000
Consider a typical two floppy disk setup, where you will have the
kernel on disk one, and have already put a RAM disk image onto disk #2.
The command line equivalent is: "prompt_ramdisk=1"
Putting that together gives 2^15 + 2^14 + 0 = 49152 for an rdev word.
-So to create disk one of the set, you would do:
+So to create disk one of the set, you would do::
/usr/src/linux# cat arch/x86/boot/zImage > /dev/fd0
/usr/src/linux# rdev /dev/fd0 /dev/fd0
/usr/src/linux# rdev -r /dev/fd0 49152
-If you make a boot disk that has LILO, then for the above, you would use:
+If you make a boot disk that has LILO, then for the above, you would use::
+
append = "ramdisk_start=0 load_ramdisk=1 prompt_ramdisk=1"
-Since the default start = 0 and the default prompt = 1, you could use:
+
+Since the default start = 0 and the default prompt = 1, you could use::
+
append = "load_ramdisk=1"
4) An Example of Creating a Compressed RAM Disk
-----------------------------------------------
+-----------------------------------------------
To create a RAM disk image, you will need a spare block device to
construct it on. This can be the RAM disk device itself, or an
Create it by writing to the RAM disk device. (This step is not currently
required, but may be in the future.) It is wise to zero out the
area (esp. for disks) so that maximal compression is achieved for
- the unused blocks of the image that you are about to create.
+ the unused blocks of the image that you are about to create::
dd if=/dev/zero of=/dev/ram0 bs=1k count=2048
-b) Make a filesystem on it. Say ext2fs for this example.
+b) Make a filesystem on it. Say ext2fs for this example::
mke2fs -vm0 /dev/ram0 2048
d) Compress the contents of the RAM disk. The level of compression
will be approximately 50% of the space used by the files. Unused
- space on the RAM disk will compress to almost nothing.
+ space on the RAM disk will compress to almost nothing::
dd if=/dev/ram0 bs=1k count=2048 | gzip -v9 > /tmp/ram_image.gz
-e) Put the kernel onto the floppy
+e) Put the kernel onto the floppy::
dd if=zImage of=/dev/fd0 bs=1k
(possibly larger) kernel onto the same floppy later without overlapping
the RAM disk image. An offset of 400 kB for kernels about 350 kB in
size would be reasonable. Make sure offset+size of ram_image.gz is
- not larger than the total space on your floppy (usually 1440 kB).
+ not larger than the total space on your floppy (usually 1440 kB)::
dd if=/tmp/ram_image.gz of=/dev/fd0 bs=1k seek=400
g) Use "rdev" to set the boot device, RAM disk offset, prompt flag, etc.
For prompt_ramdisk=1, load_ramdisk=1, ramdisk_start=400, one would
- have 2^15 + 2^14 + 400 = 49552.
+ have 2^15 + 2^14 + 400 = 49552::
rdev /dev/fd0 /dev/fd0
rdev -r /dev/fd0 49552
That is it. You now have your boot/root compressed RAM disk floppy. Some
users may wish to combine steps (d) and (f) by using a pipe.
---------------------------------------------------------------------------
+
Paul Gortmaker 12/95
Changelog:
----------
-10-22-04 : Updated to reflect changes in command line options, remove
+10-22-04 :
+ Updated to reflect changes in command line options, remove
obsolete references, general cleanup.
James Nelson (james4765@gmail.com)
-12-95 : Original Document
+12-95 :
+ Original Document
+========================================
zram: Compressed RAM based block devices
-----------------------------------------
+========================================
-* Introduction
+Introduction
+============
The zram module creates RAM based block devices named /dev/zram<id>
(<id> = 0, 1, ...). Pages written to these disks are compressed and stored
Statistics for individual zram devices are exported through sysfs nodes at
/sys/block/zram<id>/
-* Usage
+Usage
+=====
There are several ways to configure and manage zram device(-s):
+
a) using zram and zram_control sysfs attributes
b) using zramctl utility, provided by util-linux (util-linux@vger.kernel.org).
IOW, zram and zram_control sysfs attributes.
In order to get a better idea about zramctl please consult util-linux
-documentation, zramctl man-page or `zramctl --help'. Please be informed
+documentation, zramctl man-page or `zramctl --help`. Please be informed
that zram maintainers do not develop/maintain util-linux or zramctl, should
you have any questions please contact util-linux@vger.kernel.org
WARNING
=======
+
For the sake of simplicity we skip error checking parts in most of the
examples below. However, it is your sole responsibility to handle errors.
zram sysfs attributes always return negative values in case of errors.
The list of possible return codes:
--EBUSY -- an attempt to modify an attribute that cannot be changed once
-the device has been initialised. Please reset device first;
--ENOMEM -- zram was not able to allocate enough memory to fulfil your
-needs;
--EINVAL -- invalid input has been provided.
+
+======== =============================================================
+-EBUSY an attempt to modify an attribute that cannot be changed once
+ the device has been initialised. Please reset device first;
+-ENOMEM zram was not able to allocate enough memory to fulfil your
+ needs;
+-EINVAL invalid input has been provided.
+======== =============================================================
If you use 'echo', the returned value that is changed by 'echo' utility,
-and, in general case, something like:
+and, in general case, something like::
echo 3 > /sys/block/zram0/max_comp_streams
if [ $? -ne 0 ];
should suffice.
-1) Load Module:
+1) Load Module
+==============
+
+::
+
modprobe zram num_devices=4
This creates 4 devices: /dev/zram{0,1,2,3}
pre-created. Default: 1.
2) Set max number of compression streams
+========================================
+
Regardless the value passed to this attribute, ZRAM will always
allocate multiple compression streams - one per online CPUs - thus
allowing several concurrent compression operations. The number of
become offline. There is no single-compression-stream mode anymore,
unless you are running a UP system or has only 1 CPU online.
-To find out how many streams are currently available:
+To find out how many streams are currently available::
+
cat /sys/block/zram0/max_comp_streams
3) Select compression algorithm
+===============================
+
Using comp_algorithm device attribute one can see available and
currently selected (shown in square brackets) compression algorithms,
change selected compression algorithm (once the device is initialised
there is no way to change compression algorithm).
-Examples:
+Examples::
+
#show supported compression algorithms
cat /sys/block/zram0/comp_algorithm
lzo [lz4]
#select lzo compression algorithm
echo lzo > /sys/block/zram0/comp_algorithm
-For the time being, the `comp_algorithm' content does not necessarily
+For the time being, the `comp_algorithm` content does not necessarily
show every compression algorithm supported by the kernel. We keep this
list primarily to simplify device configuration and one can configure
a new device with a compression algorithm that is not listed in
-`comp_algorithm'. The thing is that, internally, ZRAM uses Crypto API
+`comp_algorithm`. The thing is that, internally, ZRAM uses Crypto API
and, if some of the algorithms were built as modules, it's impossible
to list all of them using, for instance, /proc/crypto or any other
method. This, however, has an advantage of permitting the usage of
custom crypto compression modules (implementing S/W or H/W compression).
4) Set Disksize
+===============
+
Set disk size by writing the value to sysfs node 'disksize'.
The value can be either in bytes or you can use mem suffixes.
-Examples:
+Examples::
+
# Initialize /dev/zram0 with 50MB disksize
echo $((50*1024*1024)) > /sys/block/zram0/disksize
size of the disk when not in use so a huge zram is wasteful.
5) Set memory limit: Optional
+=============================
+
Set memory limit by writing the value to sysfs node 'mem_limit'.
The value can be either in bytes or you can use mem suffixes.
In addition, you could change the value in runtime.
-Examples:
+Examples::
+
# limit /dev/zram0 with 50MB memory
echo $((50*1024*1024)) > /sys/block/zram0/mem_limit
# To disable memory limit
echo 0 > /sys/block/zram0/mem_limit
-6) Activate:
+6) Activate
+===========
+
+::
+
mkswap /dev/zram0
swapon /dev/zram0
mount /dev/zram1 /tmp
7) Add/remove zram devices
+==========================
zram provides a control interface, which enables dynamic (on-demand) device
addition and removal.
attribute. This will return either new device's device id (meaning that you
can use /dev/zram<id>) or error code.
-Example:
+Example::
+
cat /sys/class/zram-control/hot_add
1
To remove the existing /dev/zramX device (where X is a device id)
-execute
+execute::
+
echo X > /sys/class/zram-control/hot_remove
-8) Stats:
+8) Stats
+========
+
Per-device statistics are exported as various nodes under /sys/block/zram<id>/
A brief description of exported device attributes. For more details please
read Documentation/ABI/testing/sysfs-block-zram.
+====================== ====== ===============================================
Name access description
----- ------ -----------
+====================== ====== ===============================================
disksize RW show and set the device's disk size
initstate RO shows the initialization state of the device
reset WO trigger device reset
-mem_used_max WO reset the `mem_used_max' counter (see later)
-mem_limit WO specifies the maximum amount of memory ZRAM can use
- to store the compressed data
-writeback_limit WO specifies the maximum amount of write IO zram can
- write out to backing device as 4KB unit
+mem_used_max WO reset the `mem_used_max` counter (see later)
+mem_limit WO specifies the maximum amount of memory ZRAM can
+ use to store the compressed data
+writeback_limit WO specifies the maximum amount of write IO zram
+ can write out to backing device as 4KB unit
writeback_limit_enable RW show and set writeback_limit feature
-max_comp_streams RW the number of possible concurrent compress operations
+max_comp_streams RW the number of possible concurrent compress
+ operations
comp_algorithm RW show and change the compression algorithm
compact WO trigger memory compaction
debug_stat RO this file is used for zram debugging purposes
backing_dev RW set up backend storage for zram to write out
idle WO mark allocated slot as idle
+====================== ====== ===============================================
User space is advised to use the following files to read the device statistics.
layer and, thus, not available in zram<id>/stat file. It consists of a
single line of text and contains the following stats separated by
whitespace:
- failed_reads the number of failed reads
- failed_writes the number of failed writes
- invalid_io the number of non-page-size-aligned I/O requests
+
+ ============= =============================================================
+ failed_reads The number of failed reads
+ failed_writes The number of failed writes
+ invalid_io The number of non-page-size-aligned I/O requests
notify_free Depending on device usage scenario it may account
+
a) the number of pages freed because of swap slot free
- notifications or b) the number of pages freed because of
- REQ_OP_DISCARD requests sent by bio. The former ones are
- sent to a swap block device when a swap slot is freed,
- which implies that this disk is being used as a swap disk.
+ notifications
+ b) the number of pages freed because of
+ REQ_OP_DISCARD requests sent by bio. The former ones are
+ sent to a swap block device when a swap slot is freed,
+ which implies that this disk is being used as a swap disk.
+
The latter ones are sent by filesystem mounted with
discard option, whenever some data blocks are getting
discarded.
+ ============= =============================================================
File /sys/block/zram<id>/mm_stat
The stat file represents device's mm statistics. It consists of a single
line of text and contains the following stats separated by whitespace:
+
+ ================ =============================================================
orig_data_size uncompressed size of data stored in this disk.
This excludes same-element-filled pages (same_pages) since
no memory is allocated for them.
No memory is allocated for such pages.
pages_compacted the number of pages freed during compaction
huge_pages the number of incompressible pages
+ ================ =============================================================
File /sys/block/zram<id>/bd_stat
The stat file represents device's backing device statistics. It consists of
a single line of text and contains the following stats separated by whitespace:
+
+ ============== =============================================================
bd_count size of data written in backing device.
Unit: 4K bytes
bd_reads the number of reads from backing device
Unit: 4K bytes
bd_writes the number of writes to backing device
Unit: 4K bytes
+ ============== =============================================================
+
+9) Deactivate
+=============
+
+::
-9) Deactivate:
swapoff /dev/zram0
umount /dev/zram1
-10) Reset:
- Write any positive value to 'reset' sysfs node
- echo 1 > /sys/block/zram0/reset
- echo 1 > /sys/block/zram1/reset
+10) Reset
+=========
+
+ Write any positive value to 'reset' sysfs node::
+
+ echo 1 > /sys/block/zram0/reset
+ echo 1 > /sys/block/zram1/reset
This frees all the memory allocated for the given device and
resets the disksize to zero. You must set the disksize again
before reusing the device.
-* Optional Feature
+Optional Feature
+================
-= writeback
+writeback
+---------
With CONFIG_ZRAM_WRITEBACK, zram can write idle/incompressible page
to backing storage rather than keeping it in memory.
-To use the feature, admin should set up backing device via
+To use the feature, admin should set up backing device via::
- "echo /dev/sda5 > /sys/block/zramX/backing_dev"
+ echo /dev/sda5 > /sys/block/zramX/backing_dev
before disksize setting. It supports only partition at this moment.
-If admin want to use incompressible page writeback, they could do via
+If admin want to use incompressible page writeback, they could do via::
- "echo huge > /sys/block/zramX/write"
+ echo huge > /sys/block/zramX/write
To use idle page writeback, first, user need to declare zram pages
-as idle.
+as idle::
- "echo all > /sys/block/zramX/idle"
+ echo all > /sys/block/zramX/idle
From now on, any pages on zram are idle pages. The idle mark
will be removed until someone request access of the block.
IOW, unless there is access request, those pages are still idle pages.
-Admin can request writeback of those idle pages at right timing via
+Admin can request writeback of those idle pages at right timing via::
- "echo idle > /sys/block/zramX/writeback"
+ echo idle > /sys/block/zramX/writeback
With the command, zram writeback idle pages from memory to the storage.
To overcome the concern, zram supports "writeback_limit" feature.
The "writeback_limit_enable"'s default value is 0 so that it doesn't limit
any writeback. IOW, if admin want to apply writeback budget, he should
-enable writeback_limit_enable via
+enable writeback_limit_enable via::
$ echo 1 > /sys/block/zramX/writeback_limit_enable
assigned via /sys/block/zramX/writeback_limit is meaninless.)
If admin want to limit writeback as per-day 400M, he could do it
-like below.
+like below::
$ MB_SHIFT=20
$ 4K_SHIFT=12
$ echo 1 > /sys/block/zram0/writeback_limit_enable
If admin want to allow further write again once the bugdet is exausted,
-he could do it like below
+he could do it like below::
$ echo $((400<<MB_SHIFT>>4K_SHIFT)) > \
/sys/block/zram0/writeback_limit
-If admin want to see remaining writeback budget since he set,
+If admin want to see remaining writeback budget since he set::
$ cat /sys/block/zramX/writeback_limit
-If admin want to disable writeback limit, he could do
+If admin want to disable writeback limit, he could do::
$ echo 0 > /sys/block/zramX/writeback_limit_enable
If admin want to measure writeback count in a certain period, he could
know it via /sys/block/zram0/bd_stat's 3rd column.
-= memory tracking
+memory tracking
+===============
With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the
zram block. It could be useful to catch cold or incompressible
pages of the process with*pagemap.
+
If you enable the feature, you could see block state via
-/sys/kernel/debug/zram/zram0/block_state". The output is as follows,
+/sys/kernel/debug/zram/zram0/block_state". The output is as follows::
300 75.033841 .wh.
301 63.806904 s...
302 63.806919 ..hi
-First column is zram's block index.
-Second column is access time since the system was booted
-Third column is state of the block.
-(s: same page
-w: written page to backing store
-h: huge page
-i: idle page)
+First column
+ zram's block index.
+Second column
+ access time since the system was booted
+Third column
+ state of the block:
+
+ s:
+ same page
+ w:
+ written page to backing store
+ h:
+ huge page
+ i:
+ idle page
First line of above example says 300th block is accessed at 75.033841sec
and the block's state is huge so it is written back to the backing
S: Maintained
L: linux-block@vger.kernel.org
L: nbd@other.debian.org
-F: Documentation/blockdev/nbd.txt
+F: Documentation/blockdev/nbd.rst
F: drivers/block/nbd.c
F: include/trace/events/nbd.h
F: include/uapi/linux/nbd.h
M: Tim Waugh <tim@cyberelk.net>
L: linux-parport@lists.infradead.org (subscribers-only)
S: Maintained
-F: Documentation/blockdev/paride.txt
+F: Documentation/blockdev/paride.rst
F: drivers/block/paride/
PARISC ARCHITECTURE
RAMDISK RAM BLOCK DEVICE DRIVER
M: Jens Axboe <axboe@kernel.dk>
S: Maintained
-F: Documentation/blockdev/ramdisk.txt
+F: Documentation/blockdev/ramdisk.rst
F: drivers/block/brd.c
RANCHU VIRTUAL BOARD FOR MIPS
L: linux-kernel@vger.kernel.org
S: Maintained
F: drivers/block/zram/
-F: Documentation/blockdev/zram.txt
+F: Documentation/blockdev/zram.rst
ZS DECSTATION Z85C30 SERIAL DRIVER
M: "Maciej W. Rozycki" <macro@linux-mips.org>
If you want to use the floppy disk drive(s) of your PC under Linux,
say Y. Information about this driver, especially important for IBM
Thinkpad users, is contained in
- <file:Documentation/blockdev/floppy.txt>.
+ <file:Documentation/blockdev/floppy.rst>.
That file also contains the location of the Floppy driver FAQ as
well as location of the fdutils package used to configure additional
parameters of the driver at run time.
your computer's parallel port. Most of them are actually IDE devices
using a parallel port IDE adapter. This option enables the PARIDE
subsystem which contains drivers for many of these external drives.
- Read <file:Documentation/blockdev/paride.txt> for more information.
+ Read <file:Documentation/blockdev/paride.rst> for more information.
If you have said Y to the "Parallel-port support" configuration
option, you may share a single port between your printer and other
userland (making server and client physically the same computer,
communicating using the loopback network device).
- Read <file:Documentation/blockdev/nbd.txt> for more information,
+ Read <file:Documentation/blockdev/nbd.rst> for more information,
especially about where to find the server code, which runs in user
space and does not need special kernel support.
during the initial install of Linux.
Note that the kernel command line option "ramdisk=XX" is now obsolete.
- For details, read <file:Documentation/blockdev/ramdisk.txt>.
+ For details, read <file:Documentation/blockdev/ramdisk.rst>.
To compile this driver as a module, choose M here: the
module will be called brd. An alias "rd" has been defined
pr_cont("\n");
} else
DPRINT("botched floppy option\n");
- DPRINT("Read Documentation/blockdev/floppy.txt\n");
+ DPRINT("Read Documentation/blockdev/floppy.rst\n");
return 0;
}
It has several use cases, for example: /tmp storage, use as swap
disks and maybe many more.
- See Documentation/blockdev/zram.txt for more information.
+ See Documentation/blockdev/zram.rst for more information.
config ZRAM_WRITEBACK
bool "Write back incompressible or idle page to backing device"
With /sys/block/zramX/{idle,writeback}, application could ask
idle page's writeback to the backing device to save in memory.
- See Documentation/blockdev/zram.txt for more information.
+ See Documentation/blockdev/zram.rst for more information.
config ZRAM_MEMORY_TRACKING
bool "Track zRam block status"
of zRAM. Admin could see the information via
/sys/kernel/debug/zram/zramX/block_state.
- See Documentation/blockdev/zram.txt for more information.
+ See Documentation/blockdev/zram.rst for more information.
- mkfs/ mkfs.ext4
For more information please refer:
-kernel-source-tree/Documentation/blockdev/zram.txt
+kernel-source-tree/Documentation/blockdev/zram.rst
projects / thirdparty / kernel / stable.git / commitdiff
